Showing papers by "Francis Verpoort published in 2022"

Nurturing the marriages of single atoms with atomic clusters and nanoparticles for better heterogeneous electrocatalysis

Abstract: Single‐atom catalysts, featuring some of the most unique activities, selectivity, and high metal utilization, have been extensively studied over the past decade. Given their high activity, selectivity, especially towards small molecules or key intermediate conversions, they can be synergized together with other active species (typically other single atoms, atomic clusters, or nanoparticles) in either tandem or parallel or both, leading to much better performance in complex catalytic processes. Although there have been reports on effectively combining the multiple components into one single catalytic entity, the combination and synergy between single atoms and other active species have not been reviewed and examined in a systematic manner. Herein, in this overview, the key synergistic interactions, binary complementary effects, and the bifunctional functions of single atoms with other active species are defined and discussed in detail. The integration functions of their marriages are investigated with particular emphasis on the homogeneous and heterogeneous combinations, spatial distribution, synthetic strategies, and the thus‐derived outstanding catalytic performance, together with new light shined on the catalytic mechanisms by zooming in several case studies. The dynamic nature of each of the active species and in particular their interactions in such new catalytic entities in the heterogeneous electrocatalytic processes are visited, on the basis of the in situ/operando evidence. Last, we feature the current challenges and future perspectives of these integrated catalytic entities that can offer guidance for advanced catalyst design by the rational combination and synergy of binary or multiple active species.

A physicochemical introspection of porous organic polymer photocatalysts for wastewater treatment.

Abstract: Over the past decade, porous organic polymers (POPs) have emerged as powerful photocatalysts for organic transformations and wastewater decontamination. The surface properties and pore space of POPs have been tailored to find optimal physical dimensions for adsorption and catalysis, whereas playing with the donor-acceptor building units lends them unique prospects for bandgap engineering, beneficial for customized applications including the degradation of simple as well as persistent pollutants. Here in this critical perspective, we focused beyond these generic scenarios and provided a detailed physicochemical explanation for the experimental observations. Considering the invaluable role of excitons, along with mobile electrons and holes, we fundamentally justified the reactivities of POPs with regard to water treatment. Both semiconducting and molecular catalyst approaches have been considered for different types of POPs. Depending on the porosity, structural formation and defects in the POP backbone, the exciton formation, charge separation, charge diffusion, etc. are critically explained, highlighting the influence of the dielectric constant and skeletal polarizability of the material. The translation of this fundamental understanding to various reactive oxygen species generation through charge transfer (e.g., O2˙-) and exciton-exciton annihilation (e.g., 1O2) by proximity-induced FRET or Dexter pathways is discussed. The role of the hydrophilic POP skeleton in overall in-water photochemical applications is also discussed. Finally, the gaps in the current state-of-the-art are considered and the future prospects to mitigate these issues are argued.

Tandem Reactions Based on the Cyclization of Carbon Dioxide and Propargylic Alcohols: Derivative Applications of α-Alkylidene Carbonates

Abstract: As a well-known greenhouse gas, carbon dioxide (CO2) has attracted increasing levels of attention in areas of energy, environment, climate, etc. Notably, CO2 is an abundant, nonflammable, and renewable C1 feedstock in view of chemistry. Therefore, the transformation of CO2 into organic compounds is an extremely attractive research topic in modern green and sustainable chemistry. Among the numerous CO2 utilization methods, carboxylative cycloaddition of CO2 into propargylic alcohols is an ideal route due to the corresponding products, α-alkylidene cyclic carbonates, which are a series of highly functionalized compounds that supply numerous potential methods for the construction of various synthetically and biologically valuable agents. This cyclization reaction has been intensively studied and systematically summarized, in the past years. Therefore, attention has been gradually transferred to produce more derivative compounds. Herein, the tandem reactions of this cyclization with hydration, amination, alcoholysis, and isomerization to synthesize α-hydroxyl ketones, oxazolidinones, carbamates, unsymmetrical carbonates, tetronic acids, ethylene carbonates, etc. were systematically reviewed.

Electrocatalytic Water Oxidation: An Overview With an Example of Translation From Lab to Market

Abstract: Water oxidation has become very popular due to its prime role in water splitting and metal–air batteries. Thus, the development of efficient, abundant, and economical catalysts, as well as electrode design, is very demanding today. In this review, we have discussed the principles of electrocatalytic water oxidation reaction (WOR), the electrocatalyst and electrode design strategies for the most efficient results, and recent advancement in the oxygen evolution reaction (OER) catalyst design. Finally, we have discussed the use of OER in the Oxygen Maker (OM) design with the example of OM REDOX by Solaire Initiative Private Ltd. The review clearly summarizes the future directions and applications for sustainable energy utilization with the help of water splitting and the way forward to develop better cell designs with electrodes and catalysts for practical applications. We hope this review will offer a basic understanding of the OER process and WOR in general along with the standard parameters to evaluate the performance and encourage more WOR-based profound innovations to make their way from the lab to the market following the example of OM REDOX.

Synthesis of 3D Cadmium(II)-Carboxylate Framework Having Potential for Co-Catalyst Free CO2 Fixation to Cyclic Carbonates

Abstract: Metal-organic frameworks (MOFs) are porous coordination polymers with interesting structural frameworks, properties, and a wide range of applications. A novel 3D cadmium(II)-carboxylate framework, CdMOF ([Cd2(L)(DMF)(H2O)2]n), was synthesized by the solvothermal method using a tetracarboxylic bridging linker having amide functional moieties. The CdMOF crystal structure exists in the form of a 3D layer structure. Based on the single-crystal X-ray diffraction studies, the supramolecular assembly of CdMOF is explored by Hirshfeld surface analysis. The voids and cavities analysis is performed to check the strength of the crystal packing in CdMOF. The CdMOF followed a multistage thermal degradation pattern in which the solvent molecules escaped around 200 °C and the structural framework remained stable till 230 °C. The main structural framework collapsed (>60 wt.%) into organic volatiles between 400–550 °C. The SEM morphology analyses revealed uniform wedge-shaped rectangular blocks with dimensions of 25–100 μm. The catalytic activity of CdMOF for the solvent and cocatalyst-free cycloaddition of CO2 into epichlorohydrin was successful with 100% selectivity. The current results revealed that this 3D CdMOF is more active than the previously reported CdMOFs and, more interestingly, without using a co-catalyst. The catalyst was easily recovered and reused, having the same performance.

Paracetamol removal from water using N-doped activated carbon derived from coconut shell: Kinetics, equilibrium, cost analysis, heat contributions, and molecular-level insight

Abstract: Activated carbon (AC) and char derived from coconut shell were modified using urea and KOH to achieve N-doped AC. The effect of activated temperature and gas agent was studied. The series of adsorbents was characterized and it was found that the pore size and surface functional group were developed thoroughly. Paracetamol (PC) removal from aqueous solution was accomplished by adsorption in a batch system at 298 K. The intraparticle diffusion model was suitable to describe the kinetic PC removal from water rather than other models because of a complicated adsorption process in the pore connection of actual materials. The maximum capacity of these adsorbents was in a range of 39.9–357.1 mg/g, promoting them as an alternative adsorbent. Among them, the N-doped AC had the highest surface area (538 m 2 /g) and the highest PC adsorption capacity. The PC equilibrium uptakes in these samples were not pH-dependent, indicating that the pore size is the most dominant factor than the electrostatic charge of functional group on the solid surface for adsorption, which is evidenced in our simulation results. Furthermore, a Grand Canonical Monte Carlo simulation was used to study equilibrium adsorption. The effect of pore size and functional group type (carboxylic, hydroxyl, carbonyl, quaternary-N, pyrrolic-N, and pyridinic-N) were investigated on PC-water mixtures at 298 K. The heat contributions including fluid-fluid, fluid-solid, and fluid-functional group interactions of each adsorbate were investigated. The maximum capacity was found in the pore size of 0.70 nm, which was the best fit for complete monolayer coverage of PC molecules. The simulation confirmed that N-group types, especially pyridinic-N were more attractive than O-group types for enhanced PC removal. This work provided a new strategy to develop the optimal pore size and functional group type of ACs for high capacity of PC removal from aqueous solution. The estimated costs of production for char, AC, and N-doped AC were about 0.73, 2.63, and 3.83 U.S.$/kg respectively, indicating a highly competitive cost in the market. However, the N-doped AC was the cheapest price in order to remove the same amount of PC from aqueous solution. • Surface modification of N-doped activated carbon derived from coconut shell. • Nitrogen and oxygen functional group types were investigated using GCMC simulation. • The maximum capacity of paracetamol (PC) was found in pore width of 0.7 nm. • N-group types especially pyridinic-N gave the highest PC removal capacity. • The modification can enhance pyridinic-N group on the surface of N-doped AC.

Investigation of Sulfonium-Iodide-Based Ionic Liquids to Inhibit Corrosion of API 5L X52 Steel in Different Flow Regimes in Acid Medium

Abstract: The present work deals with the corrosion inhibition mechanism of API 5L X52 steel in 1 M H2SO4 employing the ionic liquid (IL) decyl(dimethyl)sulfonium iodide [DDMS+I–]. Such a mechanism was elicited by the polarization resistance (Rp), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) techniques, both in stationary and dynamic states. The electrochemical results indicated that the corrosion inhibition was controlled by a charge transfer process and that the IL behaved as a mixed-type corrosion inhibitor (CI) with anodic preference. The experimental results revealed maximal inhibition efficiency (IE) rates up to 93% at 150 ppm in the stationary state, whereas in turbulent flow, the IE fell to 65% due to the formation of microvortexes that promoted higher desorption of IL molecules from the surface. The Gibbs free energy of adsorption (ΔG°ads) value of −34.89 kJ mol–1, obtained through the Langmuir isotherm, indicated the formation of an IL monolayer on the metal surface by combining physisorption and chemisorption. The surface analysis techniques confirmed the presence of FexOy, FeOOH, and IL on the surface and showed that corrosion damage diminished in the presence of IL. Furthermore, the quantum chemistry calculations (DFT) indicated that the iodide anion hosted most of the highest occupied molecular orbital (HOMO), which eased its adsorption on the anodic sites, preventing the deposition of sulfate ions on the electrode surface.

Two-Dimensional Zeolitic Imidazolate Framework ZIF-L: A Promising Catalyst for Polymerization

Abstract: Here, for the first time, a 2D and leaf-like zeolitic imidazolate framework (ZIF-L) is reported for the synthesis of ultrahigh molecular weight (UHMW) poly(methyl methacrylate) (PMMA) with Mn up to 1390 kg mol−1. This synthesis method is a one-step process without any co-catalyst in a solvent-free medium. SEM, PXRD, FT-IR, TGA, and nitrogen sorption measurements confirmed the 2D and leaf-like structure of ZIF-L. The results of PXRD, SEM, TGA demonstrate that the catalyst ZIF-L is remarkably stable even after a long-time polymerization reaction. Zwitterionic Lewis pair polymerization (LPP) has been proposed for the catalytic performance of ZIF-L on methyl methacrylate (MMA) polymerization. This MMA polymerization is consistent with a living system, where ZIF-L could reinitiate the polymerization and propagates the process by gradually growing the polymer chains.

CO2-Induced Dissolution of ZnO into Ionic Liquids and Its Catalytic Application for the Hydration of Propargylic Alcohols

Abstract: An unexpected CO2-induced dissolution of ZnO into ionic liquids was discovered. This process exhibited high dissolution speed and the dissociated mixture was applied as an efficient Zn-based catalytic system for the CO2-promoted hydration of propargylic alcohols under atmospheric pressure with broad substrate scope. Moreover, this system could be recycled and reused for at least 16 times with excellent yields continuously obtained, which is an unprecedented record for this reaction. Significantly, this system could employ waste pigments as the ZnO source and work even under flue gas atmosphere. In the mechanistic investigations, the interaction between ZnO, CO2 and ionic liquids to give N-heterocyclic carbene/CO2 adducts proved to be the key factor for this specific dissolution. These adducts were further identified to exhibit better reactivity than the normal CO2 by experimental data and density functional theory (DFT) calculations, which might be responsible for the excellent performance of the abovementioned catalytic system.

Metal Embedded Porous Carbon for Efficient CO2 Cycloaddition under Mild Conditions

Abstract: Nitrogen-doped porous carbon material was generated via thermal pyrolysis of zeolitic imidazole frameworks (ZIFs). The structure of the ZIF templates was tuned, so that the obtained product was an N-doped porous carbon-containing encapsulated metal nanoparticle. The hierarchical structural and unique properties of pyrolyzed materials are involved in further application, including catalysis. The as-synthesized porous carbon materials were applied as a catalyst for CO2 fixation on cyclic carbonates under near ambient pressure without solvent and co-catalyst. The zinc dispersion in highly porous carbon material, deriving from ZIF-8, exhibited a superior catalytic performance among the synthesized materials. The acid sites (Zn species) and the incorporated basic sites (N-species) present in the porous carbon material are essential for a high affinity for gas adsorption and CO2 conversion. Additionally, the catalyst was found to be very robust and stable during recycling studies as the catalytic performance remained high for seven cycles.

A dual‐doping strategy of LaCoO3 for optimized oxygen evolution reaction toward zinc‐air batteries application

Abstract: Perovskite‐based electrocatalysts are extensively investigated as a replacement for noble metals electrocatalysts for energy storage and conversion devices. Their interesting catalytic activity, low cost, and diversity are considered major advantages. In this work, a facile dual‐doping strategy has been conducted and yielded an astonishing upgrade of lanthanum cobaltite; fine‐tuning of both A and B sites with calcium and manganese has proven remarkably beneficial. The dual‐doping modulates the electronic configuration of both transition metals and raises the oxygen vacancies. Consequently, oxygen evolution reaction has been assessed and La0.8Ca0.2Mn0.2Co0.8O3 showed significantly improved overpotential and maximal current density in comparison with pristine LaCoO3. Furthermore, the ZAB exhibited a high open circuit potential and superior charge‐discharge cyclability, compared to Pt/C‐based electrodes. The current work explores the influence of simultaneous doping of the A and B sites in lanthanum perovskite oxides on electrocatalytic performance to encourage further exploration of such an approach in electrocatalysis.

Carbon-Supported Cobalt Nanoparticles via Thermal Sugar Decomposition as Efficient Electrocatalysts for the Oxygen Evolution Reaction

Abstract: The sustainable fabrication of a cobalt (Co) dispersion in carbon (C) via the thermal decomposition of a sugar-based biomass with an abundant Co precursor is successfully synthesized. A foamlike architecture (Co-foam) is first generated from thermally treated sugar in the presence of Co as a catalyst. Co embedded in C (Co/C) is obtained by following a pyrolysis process. The material properties are extensively characterized and indicate a well dispersion of Co species (metallic and nanoparticles) in the C matrix. The developed material is successfully applied as a potential electrocatalyst for the oxygen evolution reaction (OER). The optimized synthesis conditions for the electrocatalyst, Co/C-400, provide the best catalytic OER performance, with the lowest overpotential of 310 mV (10 mA·cm–2) after normalization using the electrochemically active area and a Tafel slope of 73 mV·dec–1. The high content of metallic Co nanoparticles as active sites, well-dispersed in a C matrix, efficiently promotes reactivity. Compared with the reference material (IrO2), this developed material demonstrated a high electrocatalytic performance. It is promising because it exists out of nonprecious and abundant precursors. The facile fabrication method is also environmentally friendly because no additives are applied and no toxic and hazardous formations are generated.

Cs2 CO3 -Promoted C-O Coupling Protocol Enables Solventless (Hetero)aryl Ether Synthesis under Air Atmosphere.

Abstract: In this work, a Cs2 CO3 -promoted synthetic approach was identified for (hetero)aryl ether synthesis via the C-O coupling of various (hetero)aryl chlorides and alcohols/phenol. To our delight, the reactions could be carried out under transition-metal-free and solvent-free conditions. Moreover, analytical-grade reagents and air atmosphere were readily tolerated. To showcase the practical usefulness of the present protocol, the assembly of a bioactive molecule was facilely realized and the gram-scale production of selected ether products was also efficiently accomplished. In addition, density functional theory (DFT) studies, along with a few mechanistic experiments, were conducted to elucidate a proposed reaction pathway and rationalize the pivotal role of Cs2 CO3 in promoting this process. Hopefully, this work could provide useful information for researchers who are engaging in C-O cross-coupling reactions.

State-of-the-Art Mixed Matrix Membranes (MMMs)

Abstract: The performance of most polymer membranes suffers from the trade-off relationship between permeability and selectivity [...].

Bimetallic-doped Zeolitic imidazole framework-derived Cobalt-Nitrogen-Carbon supported on reduced graphene oxide enabling efficient microwave absorption

Abstract: A bimetal (Fe/Ni) doped cobalt-nitrogen-carbon matrix (Fe/Ni-CoNC) with hierarchical architecture originating from zeolitic imidazolate framework (ZIF-67) is purposely designed. The metals within the Co-N-C matrix are well distributed. Besides, Fe/Ni-CoNC was supported on reduced graphene oxide (RGO). We demonstrate that the three-element combination can synergistically contribute to different advantages for microwave absorption. Therefore, the combination of Fe and Ni synergized the absorber to obtain a good impedance match for the best microwave absorption. The synthesized Fe/Ni-CoNC/RGO with optimized element components exhibited an excellent wave absorption of -51.6 dB at 7.2 GHz obtained with a thin thickness of 2.5 mm. When combining Fe/Ni-CoNC/RGO with a thermoset resin, namely polydicyclopentadiene (PDCPD), the final product reached a maximum absorption of -24.5 dB with a thickness of 1.5 mm. This compounding confirmed that interfacial polarization, defect polarization, and natural resonance are synchronously enhanced for improved absorption performance.

Enhanced Performance of Carbon–Selenide Composite with La0.9Ce0.1NiO3 Perovskite Oxide for Outstanding Counter Electrodes in Platinum-Free Dye-Sensitized Solar Cells

Abstract: For large-scale applications, dye-sensitized solar cells (DSSCs) require the replacement of the scarce platinum (Pt)-based counter electrode (CE) with efficient and cheap alternatives. In this respect, low-cost perovskite oxides (ABO3) have been introduced as promising additives to composite-based CEs in Pt-free DSSCs. Herein, we synthesized composites from La0.9Ce0.1NiO3 (L) perovskite oxide and functionalized-multiwall-carbon-nanotubes wrapped in selenides derived from metal-organic-frameworks (f-MWCNT-ZnSe-CoSe2, “F”). L and F were then mixed with carbon black (CB) in different mass ratios to prepare L@CB, F@CB, and L@F@CB composites. The electrochemical analysis revealed that the L@F@CB composite with a mass ratio of 1.5:3:1.5 exhibits better electrocatalytic activity than Pt. In addition, the related DSSC reached a better PCE of 7.49% compared to its Pt-based counterpart (7.09%). This improved performance is the result of the increase in the oxygen vacancy by L due to the replacement of La with Ce in its structure, leading to more active sites in the L@F@CB composites. Moreover, the F@CB composite favors the contribution to the high electrical conductivity of the hybrid carbon nanotube–carbon black, which also offers good stability to the L@F@CB CE by not showing any obvious change in morphology and peak-to-peak separation even after 100 cyclic voltammetry cycles. Consequently, the corresponding L@F@CB-based device achieved enhanced stability. Our work demonstrates that L@F@CB composites with a low cost are excellent alternatives to Pt CE in DSSCs.

Benzimidazole-based N-heterocyclic carbene silver complexes as catalysts for the formation of carbonates from carbon dioxide and epoxides

Abstract: • A series of novel mononuclear and dinuclear Silver(I)-NHC complexes are synthesized and characterized. • Very low catalyst loading (0.1 mol%) is required for the carbon dioxide insertion into epoxides. • No solvent and co-catalyst are required using the Ag-compounds. • Catalysts are highly robust demonstrating excellent conversions selectivity > 99 %. • The novel catalyst is highly active amongst the reported silver catalysts for CO 2 /epoxides couplings. A series of left-to-right inequivalent 1,3-disubstituted benzimidazolium halide pro-ligands having the general formula [ R BNHC CH2OxMe ][X] (R = 3-Me-Bn, 3,5-Me 2 -Bn, 2,4,6-Me 3 -Bn, 2,3,5,6-Me 4 -Bn, 2,3,4,5,6-Me 5 -Bn, 3,4,5-(OMe) 3 -Bn, or 4- t Bu-Bn; X = Cl, Br) were synthesized by the alkylation of 1-((3-methyloxetan-3-yl)methyl)benzimidazole. The corresponding Ag complexes, ( R BNHC CH2OxMe )AgX, were prepared following pro-ligand addition to Ag 2 O. These compounds were characterized using spectroscopic techniques such as FT-IR, NMR spectroscopy, and single-crystal X-ray diffraction. The solid-state structure of ( 3-Me-Bn BNHC CH2OxMe )AgCl revealed a linear monomer while [( 2,4,6-Me3-Bn BNHC CH2OxMe )AgCl] 2 was found to exist as a dimer with pseudo trigonal planar geometry about each metal center. The synthesized ( R BNHC CH2OxMe )AgX complexes were found to be efficient for the addition of carbon dioxide to epoxides to yield value-added cyclic carbonates at ambient pressure. Amongst the investigated complexes, the bimetallic complex [( 2,4,6-Me3-Bn BNHC CH2OxMe )AgCl] 2 was found to be the most active for CO 2 insertion, exhibiting favorable activity when compared to known NHC complexes.

Application of templating-free chromium therephtalate for the adsorption of nitrogen-containing compounds in oil refinining feedstocks. Kinetics and thermodinamycs

Abstract: ABSTRACT A new simple and high scale hydrothermal synthesis of MIL-101Cr without the use of templating agent was carried out, with yields of up to 83% respective to Cr+3 with excellent textural properties. Four samples of MOF were prepared at different reaction times, and, after activation, these were studied for their nitrogen-containing compounds (NCCs) adsorption properties over straight run gasoil-light/cyclic oil (SRGO/LCO) feedstocks from oil refinery processes, containing 400 ppm of N. From the adsorption models studied, the Freundlich isotherm model better fitted the NCCs uptake, with R2 up to 0.9982 (RMSE = 0.3). According to the adsorption kinetics experiments, a pseudo second-order behavior (R2 = 0.99, RMSE = 0.067) was shown by the adsorbents with 10 min activation time. The max. NCCs adsorption capacity obtained was 19.49 mg/g. Furthermore, from the thermodynamic analysis, a ∆G0 as low as −24.6 kJ/mol showed that the adsorption process is extremely spontaneous, implicating excellent applicability at real industrial level. Up to 99.85% of non-reacted Cr+3 from MOF synthesis was perfectly recovered by precipitation with ammonia solution. Analysis of the mechanical stirring and static hydrothermal synthesis of MIL-101 Cr did not yield significant difference on the adsorption conditions, which represents an excellent energetically economic process.