Showing papers in "Dalton Transactions in 2020"

A practical guide to calculate the isosteric heat/enthalpy of adsorption via adsorption isotherms in metal-organic frameworks, MOFs.

Abstract: Porous materials such as MOFs are interesting candidates for gas separation and storage. An important parameter to gain deeper insights to the adsorption process of an adsorptive on an adsorbent is the isosteric enthalpy of adsorption, ΔHads which is defined as the heat to be released/required when an adsorptive binds to/detaches from the solid surface of an adsorbent. Two or three adsorption isotherms at different but close temperatures with ΔT ≤ 20 K for two and ΔT ≈ 10 K for three isotherms are the basis to derive the isosteric enthalpy of adsorption through the Clausius-Clapeyron approach or the virial analysis. This Perspective presents the procedure of the common (dual-site) Freundlich-Langmuir fit/Clausius-Clapeyron approach and the virial fit of the isotherms with usable Excel sheets and Origin files for the subsequent derivation of ΔHads. Exemplary adsorption isotherms of CO2, SO2 and H2 at two temperatures on MOFs are analyzed. The detailed computational description and comparison of the Clausius-Clapeyron approach and the virial analysis to determine ΔHads outlines the limitations of the two methods with respect to the available experimental data, especially at low pressure/low uptake values. It is emphasized that no extrapolation beyond the experimental data range should be done. The quality of the important and underlying isotherm fits must be checked and ensured with logarithmic-scale n/p isotherm plots for the (dual-site) Freundlich-Langmuir fit in the low-pressure region and through low standard deviations for the coefficients in the virial analysis.

Ionic liquid induced highly dense assembly of porphyrin in MOF nanosheets for photodynamic therapy

Abstract: Two-dimensional (2D) metal-organic framework (MOF) nanosheets have emerged as a new member of 2D nanomaterials for molecular sieving, energy conversion and storage, catalysis and biomedicine. In this paper, a highly dense assembly of porphyrin achievable in porphyrin-integrated MOF nanosheets induced by an ionic liquid is obtained by sonication exfoliation of its bulk crystals. The 2D layered structure MOF, [BMI]2[Ca3(H2TCPP)2(μ2-OH2)2(H2O)2] (1), was firstly prepared by using the ionic liquid assisted synthetic method (H6TCPP = meso-tetra(carboxyphenyl) porphyrin, BMI = 1-butyl-3-methylimidazolium). The laminated layers in 1 clearly indicate a weak interlayer non-covalent interaction but a strong metal-carboxylate bonding within the layers, which facilitates the exfoliation of 1 to form 2D MOF nanosheets (1 NSs). Powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM) and fast Fourier transform (FFT) patterns revealed that 1 NSs could maintain their crystalline structure after exfoliation. These MOF nanosheets exhibited excellent aqueous dispersibility, biodegradability and high cytotoxicity under light irradiation against MCF-7 cells.

Cage-like silsesquioxanes-based hybrid materials.

Abstract: Cage-like silsesquioxanes are considered to be ideal and versatile building blocks of hybrid materials due to their unique structures and excellent performance. This Perspective highlights recent advances in the field of cage-like silsesquioxane-based hybrid materials, ranging from monomer functionalization and materials preparation to application. The existing issues are reviewed and the challenges and prospects in this field are also discussed for further development and exploitation.

Recent advances in MOF-based nanoplatforms generating reactive species for chemodynamic therapy

Abstract: Still today, cancer remains a threat to human health. Possible common treatments to cure this disease include chemotherapy (CT), radiotherapy (RT), photothermal therapy (PTT), and surgical resection, which give unreasonable results because of their limited efficiency and also lead to side-effects. Hence, different strategies are now being exploited to not only enhance the efficiency of these traditional therapeutic methods or treat the tumor cells but also curtail the side effects. A latest method with authentic proof of chemodynamic therapy (CDT) utilizing the Fenton reaction is now gaining importance. This approach, which is developed based on the high level of hydrogen peroxide (H2O2) in a tumor microenvironment (TME), can be used to catalyze the Fenton reaction to generate cancer cell-killing reactive oxygen species (ROS). The selection of materials is extremely important and nanomaterials offer the most likely method to facilitate CDT. Among various materials, metal-organic frameworks (MOFs) which have been extensively applied in medical areas are regarded as a promising material and possess potential for the next generation of nanotechnology. This review focuses on summarizing the use of MOFs in CDT and their synergetic therapeutics as well as the challenges, obstacles, and development.

A review: recent advances in preparations and applications of heteroatom-doped carbon quantum dots

Abstract: Carbon quantum dots (CQDs) are widely used in optoelectronic catalysis, biological imaging, and ion probes owing to their low toxicity, stable photoluminescence, and ease of chemical modification. However, the low fluorescence yield and monochromatic fluorescence of CQDs limit their practical applications. This review summarizes the commonly used approaches for improving the fluorescence efficiency of CQDs doped with non-metallic (heteroatom) elements. Herein, three types of heteroatom-doped CQDs have been investigated: (1) CQDs doped with a single heteroatom; (2) CQDs doped with two heteroatoms; and (3) CQDs doped with three heteroatoms. The limitations and future perspectives of doped CQDs from the viewpoint of producing CQDs for specific applications, especially for bioimaging and light emitting diodes, have also been discussed herein.

Investigation into antiproliferative activity and apoptosis mechanism of new arene Ru(II) carbazole-based hydrazone complexes

Abstract: Ruthenium complexes with bioactive ligands are becoming promising substitutes for platinum complexes due to their precise action against various cancers. In the present study, the synthesis of three new arene Ru(ii) complexes containing new carbazole-based hydrazone ligands of general formula [(η6-benzene)Ru(L)Cl] (1-3; L = carbazolone benzhydrazone ligands), and their anticancer properties are described. The structural characterization of the ligands and their ruthenium complexes has been realized with the aid of elemental analysis, IR, UV-vis, NMR and HR-MS techniques. The molecular structures of all three complexes have been elucidated by single crystal X-ray crystallography and reveal the existence of pseudo-octahedral geometry around the ruthenium. The in vitro cancer cell growth inhibition property of the complexes against A549 (lung carcinoma), A2780 (ovarian adenocarcinoma) and non-cancerous 16HBE (human lung bronchial epithelium) cells were examined by MTT assay. All the complexes display good cytotoxicity towards both of these types of cancer cell compared to the standard drug cisplatin, with low IC50 values. Remarkably, complex 3, which contains an electron-donating substituent, induces a significant reduction of viability in A2780 cells. The inhibition capacity of the complexes towards A2780 cells proliferation was further confirmed using 5-ethynyl-2-deoxyuridine (EdU) assay via minimal DNA synthesis. The result of the acridine orange-ethidium bromide (AO-EB) fluorescent staining assay establishes that the cytotoxicity of the complexes was mediated by apoptosis in cancer cells. Furthermore, flow cytometry using Annexin V-FITC/propidium iodide (PI) double staining determines the quantitative discrimination of early apoptosis by the externalization of phosphatidylserine. In addition, cell cycle distribution indicates that the complexes block the cell cycle progression in the S-phase. The outcome of our investigation shows the promising scope and potency of tailored arene ruthenium complexes for precise cancer chemotherapy beyond platinum drugs.

Recent advances in metalloporphyrin-based catalyst design towards carbon dioxide reduction: from bio-inspired second coordination sphere modifications to hierarchical architectures

Abstract: Research in the development of new molecular catalysts for the selective transformation of CO2 to reduced forms of carbon is attracting enormous interest from chemists. Molecular catalyst design hinges on the elaboration of ligand scaffolds to manipulate the electronic and structural properties for the fine tuning of the reactivity pattern. A cornucopia of ligand sets have been designed along this line and more and more are being reported. In this quest, the porphyrin molecular platform has been under intensive focus due to the unmatched catalytic properties of metalloporphyrins. There have been rapid advances in this particular field during the last few years wherein both electronic and structural aspects in the second coordination spheres have been addressed to shift the overpotential and improve the catalytic rates and product selectivity. Metalloporphyrins have also attracted much attention in terms of the elaboration of hybrid materials for heterogeneous catalysis. Here too, some promising activities have made metalloporphyrin derivatives serious candidates for technological implementation. This review collects the recent advances centred around the chemistry of metalloporphyrins for the reduction of CO2.

Facile preparation of a highly efficient NiZn2O4-NiO nanoflower composite grown on Ni foam as an advanced battery-type electrode material for high-performance electrochemical supercapacitors.

Abstract: The development of combined simple metal oxides and binary metal oxides on a flexible conductor has been needed as a novel approach for energy storage sources. Here, we demonstrate a simple and versatile strategy towards the synthesis of a NiZn2O4-NiO nanoflower array (NFA) composite effectively deposited into a nickel (Ni) foam conductor for energy storing applications to achieve better electrochemical results. The morphology and other physical properties of the as-developed composite were analyzed, and the results suggest that the NiO nanoparticles have been effectively anchored into the binary NiZn2O4 nanoleaves array surface. The composite NiZn2O4-NiO NFAs nanoarchitecture combines superior surface area with huge numbers of active sites to boost electrochemical reactions and excellent transport between electrons and ions, as compared to NiZn2O4 nanoleaf arrays (NLAs). Meanwhile, taking into consideration electrochemical studies, the composite NiZn2O4-NiO NFAs exhibited extraordinary faradaic redox progress, which was different from the metal oxide based electrode profiles. Cyclic voltammetry and galvanostatic charge-discharge plateaus from the NiZn2O4 NLAs and NiZn2O4-NiO NFAs electrodes exhibit faradaic battery-type redox behavior, which is distinct from the profiles of carbon-based materials. As a battery-type electrode, the composite NiZn2O4-NiO NFAs electrode exhibited a greater supercapacitor activity with a higher specific capacitance of 482.7 C g-1 at 1 A g-1 and also yielded the best life-span with up to 98.14% capacity retained after 5000 cycles (vs. 253.4 C g-1 at 1 A g-1 and 91.4% retention of capacity after 5000 cycles for NiZn2O4 NLAs), which was the best result or comparable to recently reported composites of simple metal oxides/binary metal oxides-based electrode materials. Thus, with the above findings, the battery-type NiZn2O4-NiO NFAs electrode material has remarkable application potential and could be effectively applied in other energy storage technologies.

Two-fold interpenetrated Mn-based metal-organic frameworks (MOFs) as battery-type electrode materials for charge storage.

Abstract: Two novel interpenetrated 2-fold Mn-based metal–organic frameworks (MOFs) (SC-7 and SC-8), assembled from the rigid ligand H3TATB (4,4′,4′′-s-triazine-2,4,6-triyl-tribenzoic acid) and Mn ions with the assistance of the flexible N-donor linker BIB (bis((1H-imidazol-1-yl)methyl)benzene) or TIPA (tris(4-imidazolylphenyl)amine), have been successfully prepared. The as-obtained MOFs show two distinct topological structures with the symbols 44·62 and (52·6)(53·6·73·82·9) due to discrepancies between the flexibilities of the bi-imidazole and tri-imidazole linkers. The electrodes based on the as-prepared bulk Mn-MOFs behave as alkaline batteries in electrochemical cells and deliver high capacities (279 and 172 mA h g−1 at 1 A g−1 for SC-7 and SC-8, respectively). Theoretical mechanism analyses indicate that the surface-controlled (k1v) process can be transformed into a diffusion-dominated (k2v1/2) process when the charging time exceeds 30 seconds in the MOF-based systems. Our research provides a new strategy to construct an increasing number of stable redox sites in MOFs for application to battery-capacitor hybrid devices.

The unique β-diketiminate ligand in aluminum(i) and gallium(i) chemistry.

Abstract: Over the past few decades, β-diketiminate ligands have been widely used in coordination chemistry and are capable of stabilizing various metal complexes in multiple oxidation states. Recently, the chemistry of aluminum and gallium in their +1 oxidation state has rapidly emerged. NacNacM(i) (M = Al, Ga; NacNac = β-diketiminate ligand) shows a two coordinate metal center comparable with singlet carbene-like species. The metal center also possesses a formally vacant p-orbital. In this article we present an overview of the last 10 years for aluminum(i) and gallium(i) stabilized by β-diketiminate ligands that have been widely explored in bond breaking and forming species.

Zero-concentration quenching: a novel Eu3+ based red phosphor with non-layered crystal structure for white LEDs and NaSrY(MoO4)3:Sm3+ based deep-red LEDs for plant growth

Abstract: Oxide based highly efficient narrow band red emitting phosphors are still a bottleneck in white LED applications. Trivalent europium ion based phosphors could be a better choice, however their weak oscillator strength restricts their use in white light emitting diodes (LEDs). Herein, we report a novel red emitting NaSrEu(MoO4)3 (NSEuM) phosphor with zero concentration quenching (non-layered crystal structure). The phosphors (NaSrY1−xEux(MoO4)3, x = 0.1–1, in increments of 0.1) were synthesized through a traditional solid-state reaction and their phase formations were analyzed by powder X-ray diffraction (PXRD) followed by Rietveld refinement. Under 395 nm excitation, all the phosphors showed sharp emission at 616 nm (full width at half maximum, FWHM ∼4–5 nm) owing to the 5D0 → 7F2 electric dipole transition of the Eu3+ ion. A concentration dependent photoluminescence (PL) study revealed that there is no concentration quenching of the systems, leading to them having superior emission characteristics over those of commercial red phosphors as well as a reported Eu3+ phosphor with a layered structure. The color purity of the synthesized phosphor was observed to be 96.32% and it shows excellent thermal stability at 423 K, retaining 64.6% of the emission intensity of its initial room temperature. The NSEuM phosphor shows a high absolute quantum yield of 79.7%. Besides this, a red LED (near UV (NUV) LED chip with the NaSrEu(MoO4)3 phosphor) as well as a hybrid white LED (NUV LED chip with an organic yellow dye + red NSEuM phosphor) were fabricated and their optical properties were studied. After the inclusion of the red phosphor in the hybrid white LED, the color rendering index (CRI)/correlated color temperature (CCT) were improved significantly (60/9333 K vs. 79/6004 K, respectively). In addition, to show the potential use of the system in plant growth application, we systematically investigated the Sm3+ activation in NaSrY(MoO4)3 and found that the phosphor shows orange red emission with an intense deep red emission (645 nm (4G5/2 → 6H9/2)). We fabricated a hybrid red/deep red LED by integrating a NUV LED with a mixed Sm3+ and Eu3+ phosphor and the spectral lines were well matched with the phytochrome (Pr) absorption spectrum. The presently investigated phosphor showed potential in a white LED as well as a deep red/orange-red LED for plant growth.

A hierarchical LDH/MOF nanocomposite: single, simultaneous and consecutive adsorption of a reactive dye and Cr(vi).

Abstract: The design and development of an environmentally benign porous adsorbent for effective simultaneous adsorption of organic dyes and heavy metals from water are important but remain a big challenge. Herein, we have designed a layered double hydroxide/metal-organic framework-based hierarchical nanocomposite (LDH/MOF HNC) by a facile, room-temperature in situ approach. This paper for the first time reports a hierarchical trimodal micro-meso-macroporous LDH/MOF composite with a high surface area (surface area 1282 m2 g-1 and pore volume 0.93 cm3 g-1), synthesised by uniformly growing MOF nanocrystals on the surface of LDH nanosheet ultrathin films. An attempt is made to quantitatively demonstrate the adsorption data via suitable nonlinear kinetic and isotherm equations for single, simultaneous, and consecutive adsorption of the orange II reactive dye and Cr(vi). Experiments were performed at various values of pH (6.0-11.0), adsorbent dosages (1.0-8.0 mg), adsorbate concentrations (5-500 mg L-1), and temperatures (293-323 K). The Langmuir model revealed a satisfactory fit to the equilibrium data of the LDH/MOF HNC (correlation coefficients R2 > 0.98) with a calculated maximum adsorption capacity of 1173 and 733 mg g-1 for orange II and Cr(vi), respectively, in a simultaneous adsorption system. The results of the study demonstrated that LDH/MOF HNCs could potentially be applied as a promising nanoadsorbent for the simultaneous removal and extraction of toxic dyes and metals from water.

A novel electrode for supercapacitors: efficient PVP-assisted synthesis of Ni3S2 nanostructures grown on Ni foam for energy storage

Abstract: In this academic research, we report the polyvinylpyrrolidone (PVP) assisted synthesis of a Ni3S2 electrode material containing a plentiful number of active sites on Ni foam by a novel hydrothermal approach. Interestingly, the Ni3S2 electrode is a highly efficient electroactive material, as evidenced by the physical and electrochemical characterization. Based on the physical characterization, the constructed Ni3S2 nano architecture exhibited plentiful electroactive sites, quick charge/discharge transportation and better maximum conductivity, which gave rise to enhanced electrochemical activity for large-scale supercapacitors (SCs). Besides, the electrochemical characterization of the as-developed Ni3S2 electrode obviously displayed a faradaic battery-based redox profile, which is distinct from the profiles of carbon-type materials. The battery-based PVP-assisted Ni3S2 electrode achieved impressive electrochemical activity, namely exceptional SC activity with a superior specific capacity of ∼316.8 mA h g-1 at 2 A g-1 current density, high rate capability with ∼91.4% of capacity retained at 20 A g-1, and superb cycling performance with ∼96.7% of capacity retained at 6 A g-1 after 4000 cycles. Thus, considering the best findings above, the as-developed PVP-assisted Ni3S2 is a highly efficient candidate for SCs and could effectively serve in various advanced energy storage applications.

A hydrostable cage-based MOF with open metal sites and Lewis basic sites immobilized in the pore surface for efficient separation and purification of natural gas and C2H2.

Abstract: Design and construction of stable adsorbents for efficient separation and purification of natural gas and C2H2 is fundamentally important in the chemical industry, and hierarchical cage-based MOFs are attractive in this regard due to their intrinsic structural advantages. In this work, a cage-based MOF (termed ZJNU-15) assembled from a tetranuclear Cu4O-based SBU and an amine-functionalized N,O-mixed donor ligand was solvothermally constructed. Single-crystal X-ray diffraction studies showed that the resulting MOF incorporates two different types of polyhedral cages in the entire network and bears incompatible open copper sites and uncoordinated amine groups immobilized in the pore surface. In view of its intriguing structural features, its gas adsorption properties with respect to C2 hydrocarbons, CO2, and CH4 were systematically investigated, revealing that it could achieve efficient removal of C2 hydrocarbons and CO2 from CH4 as well as separation of a binary C2H2–CO2 mixed gas, which is associated with natural gas and C2H2 separation and purification. At 298 K and 1 atm, for equimolar binary components, the IAST-predicted adsorption selectivities for C2 hydrocarbons over CH4 are above 17.7, while the CO2/CH4 and C2H2/CO2 adsorption selectivities are 5.0 and 4.4, respectively. Notably, stability studies showed that the framework maintained its structural integrity after being immersed in HCl/NaOH aqueous solutions within a pH range of 4–11 at ambient temperature for 24 h, indicating its good hydrolytic stability under harsh chemical conditions, which might lay a solid foundation for its practical applications.

A versatile and multifunctional metal-organic framework nanocomposite toward chemo-photodynamic therapy.

Abstract: Previously most of the applications of targeting components have been based on the enhanced permeability and retention effect achieved using folic acid, which consider the side effects of the targeting components to some extent. Herein, we report a new strategy to decorate the surface of MOFs using a pemetrexed (MTA) targeting molecule, affording a new drug delivery system of ALA@UIO-66-NH-FAM/MTA (ALA = 5-amino-levulinic acid and FAM = 5-carboxyfluorescein). The confocal microscopy and flow cytometry results showed that ALA@UIO-66-NH-FAM/MTA presented a better targeting effect compared to ALA@UIO-66-NH-FAM/FA (FA = folic acid) and indicated a gradually increasing tendency of the targeting effect with the increasing expression of folate receptors on the tumor cell cytomembrane. Furthermore, the cytotoxicity experiment indicates that the combination of chemotherapy and photodynamic therapy is a more effective therapy model than single chemotherapy and photodynamic therapy. This work demonstrates the first attempt at folic acid antagonist (MTA) modification for NMOFs, providing a new concept for the design of MOFs with folate receptor targeting capacity for clinical applications.

First Ln-MOF as a trifunctional luminescent probe for the efficient sensing of aspartic acid, Fe3+ and DMSO

Abstract: Five 3D network Ln3+ metal-organic frameworks (Ln-MOFs) formulated as [[Ln(μ6-H2cpboda)(μ2-OH2)2]·xH2O]n [Ln3+ = La3+ (1), Nd3+ (2), Sm3+ (3), Eu3+ (4), Tb3+ (5), H2cpboda = 5,5'-((5-carboxy-1,3-phenylene)bis(oxy))diisophthalic acid] were synthesized via a hydrothermal method. They were established by single-crystal X-ray and powder diffraction analyses, elemental analysis (EA) and thermogravimetric analyses (TGAs). All the compounds are isostructural with three-dimensional structures with the point symbol of (413·62)(48·66·8) in terms of topology, and they crystallize in the monoclinic space group P21/n. Interestingly, the solid-state luminescence of complexes 4 and 5 shows intense red and green emission, respectively. Besides, the Tb-MOF (5) is a good luminescent sensor, able not only to detect aspartic acid and Fe(iii) ions with good stability, high efficiency and reversibility, but also to exhibit a rapid response and high selectivity to DMSO. To our knowledge, it is the first Ln-MOF that can act as a luminescent probe for the efficient sensing of DMSO, while the lone pair of electrons in the O of DMSO attacked the positive charge at the protonation carboxylic acid of H5cpboda. Consequently, Tb-MOF (5) is a rare and versatile fluorescent probe for aspartic acid, Fe3+ cations and DMSO, simultaneously.

A multi-responsive chemosensor for highly sensitive and selective detection of Fe3+, Cu2+, Cr2O72- and nitrobenzene based on a luminescent lanthanide metal-organic framework.

Abstract: Excessive release of some hazardous chemicals, such as Fe3+, Cu2+, Cr2O72- and nitrobenzene, may endanger public health and the environment; therefore, targeted effective sensing strategies are important In this report, a series of lanthanide-based metal-organic frameworks (Ln-MOFs), namely {[Ln(dpc)(2H2O)]·(Hbibp)05}n (H4dpc = 2-(3',4'-dicarboxylphenoxy) isophthalic acid, bibp = 4,4'-bis(imidazolyl) biphenyl, for I-VI, Ln = La, Ce, Pr, Nd, Sm, and Eu) were hydrothermally synthesized and characterized Single-crystal X-ray diffraction indicates that I-VI are isostructural and the lanthanide center is nine-coordinated with a distorted tetrakaidecahedral configuration The as-synthesized Ln-MOFs are assembled into three-dimensional frameworks through the connections of dpc4- ligands and hydrogen bonding interactions Notably, Eu-MOF (VI) behaves as a multi-responsive luminescent sensor toward Fe3+, Cu2+, Cr2O72- and nitrobenzene with high sensitivity, selectivity, stability and anti-interference ability against the coexistence of other ions or molecules based on high luminescence quenching efficiency Additionally, Eu-MOF (VI) shows excellent luminescence stability and retains its structural integrity within the pH range of 2-12 in an aqueous solution and its solid sample maintains high thermodynamic stability up to 320 °C Furthermore, the possible luminescence sensing mechanisms have been discussed in detail, and are supported by PXRD analysis, UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS) or density functional theory (DFT)

Spin dynamics in single-molecule magnets and molecular qubits

Abstract: Over recent decades, much effort has been made to lengthen spin relaxation/decoherence times of single-molecule magnets and molecular qubits by following different chemical design rules such as maximizing the total spin value, controlling symmetry, enhancing the ligand field or inhibiting key vibrational modes Simultaneously, electronic structure calculations have been employed to provide an understanding of the processes involved in the spin dynamics of molecular systems and served to refine or introduce new design rules This review focuses on contemporary theoretical approaches focused on the calculation of spin relaxation/decoherence times, highlighting their main features and scope Fundamental aspects of experimental techniques for the determination of key Single Molecule Magnet/Spin Qubit properties are also reviewed

Metal organic frameworks decorated with free carboxylic acid groups: topology, metal capture and dye adsorption properties.

Abstract: In this report, metal organic frameworks (MOFs) are designed and tuned for structural variations in order to induce metal capture which in turn directs dye adsorption properties. The three MOFs, Cu-MOF-2COOH, Ni-MOF-COOH and Cd-MOF, are synthesized by employing 1,3,5-benzenetricarboxylic acid (H3-BTC) as the main ligand and 4,4′-dipyridyl (bipy) as the spacer. The MOFs have been characterized using various spectral techniques and single crystal X-Ray studies. A topological analysis using TOPOS Pro reveals that the MOFs possess varying topologies i.e.hcb, hxl, sql and 2C1. Cu-MOF-2COOH and Ni-MOF-COOH contain two and three uncoordinated carboxylic acid groups, respectively, and in Cd-MOF, all three –COOH groups are utilized in bonding. The dye adsorption properties of the MOFs with free carboxylate group(s) were checked and we found that both MOFs are unable to adsorb any of the dyes significantly. The free carboxylate group(s) in the MOFs inspire us to elaborate their metal capturing properties. In different solvents we checked the metal capturing properties of Cu-MOF-2COOH and Ni-MOF-COOH with different metal salts. Surprisingly, both MOFs show better metal capturing properties towards the hard and highly polarizing Fe3+ ion in aqueous medium. Theoretical studies show that the free carboxylate(s) are involved in binding with metals. The post synthetically modified materials (Fe@Cu-MOF-2COOH and Fe@Ni-MOF-COOH) were further checked for their dye adsorption properties and both the doped MOFs show better adsorption properties towards the MB and MO. Furthermore, three kinetic models were employed to understand the reaction mechanism of adsorption and the pseudo second order kinetic model fits the best in both cases. The uncoordinated carboxylate groups in the channels act as post synthetic modification sites for metal capture and the post synthetically modified material thus formed attracts organic dyes following the HSAB concept. The strong interaction existing between the hard Fe3+ ion and hard donors of the dyes is responsible for the enhanced adsorption.

The highly selective detecting of antibiotics and support of noble metal catalysts by a multifunctional Eu-MOF.

Abstract: Designing novel multifunctional rare-earth metal-organic frameworks (MOFs) has attracted intensive attention. In particular, employing such materials for sensing or catalytic reactions is still very challenging. Here, a new 3D porous Eu(iii)-MOF, [Eu(cppa)(OH)]·xS (denoted as CTGU-19, S = solvent molecule, CTGU = China Three Gorges University), was synthesized by using 5-(4-carboxyphenyl)picolinic acid (H2cppa) as an organic ligand, and it shows a 3D (3,12)-connected topological net with the point symbol (420·628·818)(43)4, constructed from cubane-shaped tetranuclear europium building units. Interestingly, CTGU-19 can be used as a highly sensitive luminescent sensor to identify ornidazole (ODZ) and nitrofurantoin (NFT) at different excitation wavelengths. This result represents the first example of a lanthanide-metal-organic-framework (Eu-MOF) that can be employed as a discriminating fluorescent probe to recognize ODZ and NFT at different excitation wavelengths. Furthermore, after loading CTGU-19 with Ag and/or Au nanoparticles, the composites exhibit efficient catalytic performance for reducing 2-/3-/4-nitrophenols (2-/3-/4-NP), in which the unit mass reduction rate constants of Ag0.8Au0.2@CTGU-19 for 2-NP, 3-NP, and 4-NP reach 68.8, 53.80, and 52.34 s-1 g-1, respectively.

Immobilization of N-oxide functionality into NbO-type MOFs for significantly enhanced C2H2/CH4 and CO2/CH4 separations.

Abstract: NbO-type MOFs built up from linear diisophthalate ligands and dicopper paddlewheel-based secondary building units offer an excellent platform to perform pore surface chemistry engineering and understand the structure-property relationship. In this work, we designed and synthesized two N-oxide functionalized linear diisophthalate ligands, and employed them to construct under suitable solvothermal conditions their corresponding NbO-type MOFs termed ZJNU-19 and ZJNU-20. Their gas adsorption properties with respect to C2H2, CO2, and CH4 were systematically measured, and adsorption selectivities of C2H2 and CO2 over CH4 were assayed using a well-known ideal adsorbed solution theory, establishing their promising potential for C2H2/CH4 and CO2/CH4 separations in connection with acetylene and natural gas separation and purification, which were found to be less dependent on the methyl position. In particular, at atmospheric pressure, the C2H2 and CO2 uptake capacities reach as high as 214.5 and 114.7 cm3 (STP) g-1 for ZJNU-19, and 210.0 and 111.9 cm3 (STP) g-1 for ZJNU-20 at 295 K, while the IAST-predicted C2H2/CH4 (v/v = 1/1) and CO2/CH4 (v/v = 1/1) adsorption selectivities are up to 42.2 and 6.4 for ZJNU-19, and 42.1 and 6.2 for ZJNU-20 at 298 K. Furthermore, a comparative investigation demonstrated that N-oxide is a powerful chemical functionality that can be utilized to design and construct porous framework compounds for boosting C2H2 and CO2 adsorptions.

0D/2D spatial structure of CdxZn1−xS/Ni-MOF-74 for efficient photocatalytic hydrogen evolution

Abstract: A novel zero-dimensional/two-dimensional CdxZn1-xS/Ni-MOF-74 (CZS/NMF) heterojunction was rationally constructed via a simple hydrothermal and physical mixing method. The results show that the CZS/NMF-4 composite has the best photocatalytic hydrogen evolution performance, generating 1712.3 μmol of hydrogen within 5 h, approximately 10 times higher than the amount generated by pure CZS. This extraordinary enhanced photocatalytic hydrogen activity can be ascribed to the constitution of the direct Z-scheme heterojunction and the small size effect, as well as the intimate contact between the 0D CdxZn1-xS nanoparticles and the 2D Ni-MOF-74 sheets. The formation of the direct Z-scheme heterojunction can effectively reduce the migration resistance of light-generated carriers and dramatically promote the separation of photo-induced electrons and holes. Meanwhile, the size effect shortens the electron transfer distance which effectively decreases the recombination possibility of photo-induced electron-hole pairs. Furthermore, the 0D/2D spatial structure of CZS/NMF-4 dramatically reduces the agglomeration of CZS nanoparticles, which provides more active sites for the process of hydrogen evolution. In general, this work provides new inspiration for the application of combinations between progressively developing new MOF materials and the traditional CdxZn1-xS photocatalyst according to the construction of a special spatial structure.

Conductivity and mixed conductivity of a novel dense diffusion barrier and the sensing properties of limiting current oxygen sensors

Abstract: First-principles calculations were used to explore the effect of various Y-doping levels on the electrical conductivity of SrTiO3. Herein, we prepared ((Y0.07Sr0.93Ti0.6Fe0.4-xO3-δ)/x/3Co3O4 (x = 0.1, 0.2, 0.3)) composites using a solid state reaction method. The properties of these sensing materials and the fabricated sensors including crystal phase composition, microstructures, oxygen ionic conductivity, total conductivity and sensor performance were investigated in detail. XRD demonstrates the formation of a highly cubic perovskite structure. The introduction of Co3O4 promotes remarkably the electronic conductivity of the Y0.07Sr0.93Ti0.6Fe0.4-xO3-δ/x/3Co3O4 composites due to the formation of n-type CoO and p-type Co2O3. A limiting current oxygen sensor based on (Y0.07Sr0.93Ti0.6Fe0.4-xO3-δ)/x/3Co3O4 as a dense diffusion barrier shows excellent sensing performance. The recovery time is less than the response time, indicating that Co2O3 promotes the gas desorption reaction which results in a shorter recovery time. The obtained results demonstrate a direct relationship between limiting current (IL) and oxygen content.

Facile synthesis of Mn-doped NiCo2O4 nanoparticles with enhanced electrochemical performance for a battery-type supercapacitor electrode.

Abstract: We report the synthesis of manganese-doped nickel cobalt oxide (Mn-doped NiCo2O4) nanoparticles (NPs) by an efficient hydrothermal and subsequent calcination route. The material exhibits a homogeneous distribution of the Mn dopant and a battery-type behavior when tested as a supercapacitor electrode material. Mn-doped NiCo2O4 NPs show an excellent specific capacity of 417 C g-1 at a scan rate of 10 mV s-1 and 204.3 C g-1 at a current density of 1 A g-1 in a standard three-electrode configuration, ca. 152-466% higher than that of pristine NiCo2O4 or MnCo2O4. In addition, Mn-doped NiCo2O4 NPs showed an excellent capacitance retention of 99% after 1000 charge-discharge cycles at a current density of 2 A g-1. The symmetric solid-state supercapacitor device assembled using this material delivered an energy density of 0.87 μW h cm-2 at a power density of 25 μW h cm-2 and 0.39 μW h cm-2 at a high power density of 500 μW h cm-2. The cost-effective synthesis and high electrochemical performance suggest that Mn-doped NiCo2O4 is a promising material for supercapacitors.

What is holding back the development of antiviral metallodrugs? A literature overview and implications for SARS-CoV-2 therapeutics and future viral outbreaks.

Abstract: In light of the Covid-19 outbreak, this review brings together historical and current literature efforts towards the development of antiviral metallodrugs. Classical compounds such as CTC-96 and auranofin are discussed in depth, as pillars for future metallodrug development. From the recent literature, both cell-based results and biophysical assays against potential viral biomolecule targets are summarized here. The comprehension of the biomolecular targets and their interactions with coordination compounds are emphasized as fundamental strategies that will foment further development of metal-based antivirals. We also discuss other possible and unexplored methods for unveiling metallodrug interactions with biomolecules related to viral replication and highlight the specific challenges involved in the development of antiviral metallodrugs.

Photocatalytic, dye degradation, and bactericidal behavior of Cu-doped ZnO nanorods and their molecular docking analysis

Abstract: Nanostructures of Cu-doped ZnO (Cu:ZnO) were prepared with the chemical precipitation technique with an aim to enhance the photocatalytic and antibacterial properties of ZnO. Phase constitution, the presence of functional groups, optical properties, elemental composition, surface morphology and microstructure were evaluated using an X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectrophotometer, energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HR-TEM), respectively. Emission spectra were obtained with a photoluminescence (PL) spectroscope whereas interlayer d-spacing was estimated through HR-TEM. ZnO consisted of a hexagonal wurtzite structure. The crystallinity of the sample was observed to increase with increasing doping concentration. The addition of Cu to ZnO served to transform nanoclusters into nanorods as revealed during SEM analysis. Catalytic activity enhanced due to the formation of nanorods, and UV-Vis absorption spectra showed that methylene blue (MB) degraded more efficiently with ZnO nanoclusters compared to the NaBH4 reagent. In addition, the doped NPs showed enhanced bacterial efficiency for G +ve. Finally, a molecular docking study was undertaken to highlight the importance of the binding interactions of the Cu-doped ZnO nanorods with β-lactamase and beta-ketoacyl-acyl carrier protein synthase III (FabH) as possible enzyme targets. This research indicates that Cu-doped Zn nanorods are a highly efficient photocatalyst and can be aptly employed for wastewater treatment and antibacterial applications.

A rational design of nanoporous Cu-Co-Ni-P nanotube arrays and CoFe2Se4 nanosheet arrays for flexible solid-state asymmetric devices.

Abstract: Porous structures have attracted considerable attention as promising electrode designs for supercapacitor applications Herein, we introduce a procedure towards the construction of nanoporous CuCoNi–P nanotube arrays (CCNP-NAs) by a metal–organic framework and hierarchical CoFe2Se4 nanosheet arrays (CFS-NAs) through a hydrothermal strategy, followed by selenization for the flexible asymmetric device Due to the unique design of the electrode materials, the CCNP-NA and CFS-NA electrodes show exceptional specific capacities of ∼40673 and 2482 mA h g−1 at 2 A g−1, reasonable rate capabilities of 842 and 712% at 50 A g−1, and remarkable durability of 989% and 951%, respectively Remarkably, an advanced flexible device was constructed using the CCNP-NA positive electrode and CFS-NA negative electrode Our flexible device demonstrates tremendous energy density (∼1535 W h kg−1 at 8528 W kg−1), super-high durability of 962%, and considerable flexibility under bending conditions This work proposes insight into the rational construction of porous nanostructures for next-generation electronic devices

A reversible chromogenic covalent organic polymer for gas sensing applications

Abstract: A triazine-cored covalent organic polymer (COP) was designed and synthesized via amine linkages under ambient conditions. The novel architecture of the COP was fully characterized via spectroscopic and analytical techniques. The present COP demonstrates a quick, portable and reversible chromogenic response towards noxious HCl vapours.

Binary zinc–cobalt metal–organic framework derived mesoporous ZnCo2O4@NC polyhedron as a high-performance lithium-ion battery anode

Abstract: Ternary transition metal oxides have attracted increasing attention due to their many merits, and will enhance electrochemical performance via the synergistic effects of the different single metal oxides. Herein, ZnCo2O4 nanoparticles encapsulated in nitrogen-doped carbon (ZnCo2O4@NC) polyhedrons have been successfully prepared through a facile two-step method. The as-prepared products had a uniform size and consisted mainly of interconnected ZnCo2O4 nanoparticles (NPs), which were uniformly distributed in the materials. As a result, the ZnCo2O4@NC polyhedrons of ZnCo-700 show a superb specific capacity of approximately 1601 mA h g−1 over 50 cycles at 0.1 A g−1. A reversible capacity of 1082 mA h g−1 was retained after 300 cycles at 1 A g−1, and a superb reversible capacity of 775 mA h g−1 was attained even when the current density was increased to 5 A g−1. These distinguished electrochemical properties could be ascribed mainly to the uniquely advantageous structural and compositional features.

The chemistry of Ce-based metal-organic frameworks.

Abstract: Metal-organic frameworks (MOFs) have gained widespread attention due to their modular construction that allows the tuning of their properties. Within this vast class of compounds, metal carboxylates containing tri- and tetravalent metal ions have been in the focus of many studies due to their often high thermal and chemical stabilities. Cerium has a rich chemistry, which depends strongly on its oxidation state. Ce(iii) exhibits properties typically observed for rare earth elements, while Ce(iv) is mostly known for its oxidation behaviour. In MOF chemistry this is reflected in their unique optical and catalytic properties. The synthetic parameters for Ce(iii)- and Ce(iv)-MOFs also differ substantially and conditions must be chosen to prevent reduction of Ce(iv) for the formation of the latter. Ce(iii)-MOFs are usually reported in comprehensive studies together with those constructed with other RE elements and normally they are isostructural. They exhibit a greater structural diversity, which is reflected in the larger variety of inorganic building units. In contrast, the synthesis conditions of Ce(iv)-MOFs were only recently (2015) established. These lead selectively to hexanuclear Ce-O clusters that are well-known for Zr-MOFs and therefore very similar structural and isoreticluar chemistry is found. Hence Ce(iv)-MOFs exhibit often high porosity, while only a few porous Ce(iii)-MOFs have been described. Some of these show structural flexibility which makes them interesting for separation processes. For Ce(iv)-MOFs the redox properties are most relevant. Thus, they are intensively discussed for catalytic, photocatalytic and sensing applications. In this perspective, the synthesis, structural chemistry and properties of Ce-MOFs are summarized.