Efficient removal of organic pollutants from wastewater has become a hot research topic due to its ecological and environmental importance. Traditional water treatment methods such as adsorption, coagulation, and membrane separation suffer from high operating costs, and even generate secondary pollutants. Photocatalysis on semiconductor catalysts (TiO2, ZnO, Fe2O3, CdS, GaP, and ZnS) has demonstrated efficiency in degrading a wide range of organic pollutants into biodegradable or less toxic organic compounds, as well as inorganic CO2, H2O, NO3−, PO43−, and halide ions. However, the difficult post-separation, easy agglomeration, and low solar energy conversion efficiency of these inorganic catalysts limit their large scale applications. Exploitation of new catalysts has been attracting great attention in the related research communities. In the past two decades, a class of newly-developed inorganic–organic hybrid porous materials, namely metal–organic frameworks (MOFs) has generated rapid development due to their versatile applications such as in catalysis and separation. Recent research has showed that these materials, acting as catalysts, are quite effective in the photocatalytic degradation of organic pollutants. This review highlights research progress in the application of MOFs in this area. The reported examples are collected and analyzed; and the reaction mechanism, the influence of various factors on the catalytic performance, the involved challenges, and the prospect are discussed and estimated. It is clear that MOFs have a bright future in photocatalysis for pollutant degradation.

Photocatalytic organic pollutants degradation in metal–organic frameworks

The literature on open-framework materials has shown numerous examples of porous solids with additional structural, chemical, or physical properties. These materials show promise for applications ranging from sensing, catalysis and separation to multifunctional materials. This critical review provides an up-to-date survey to this new generation of multifunctional open-framework solids. For this, a detailed revision of the different examples so far reported will be presented, classified into five different sections: magnetic, chiral, conducting, optical, and labile open-frameworks for sensing applications. (413 references.)

Old materials with new tricks: multifunctional open-framework materials.

Li-ion batteries (LIBs), commercialized in 1991, have the highest energy density among practical secondary batteries and are widely utilized in electronics, electric vehicles, and even stationary energy storage systems. Along with the expansion of their demand and application, concern about the resources of Li and Co is growing. Therefore, secondary batteries composed of earth-abundant elements are desired to complement LIBs. In recent years, K-ion batteries (KIBs) have attracted significant attention as potential alternatives to LIBs. Previous studies have developed positive and negative electrode materials for KIBs and demonstrated several unique advantages of KIBs over LIBs and Na-ion batteries (NIBs). Thus, besides being free from any scarce/toxic elements, the low standard electrode potentials of K/K+ electrodes lead to high operation voltages competitive to those observed in LIBs. Moreover, K+ ions exhibit faster ionic diffusion in electrolytes due to weaker interaction with solvents and anions than that of Li+ ions; this is essential to realize high-power KIBs. This review comprehensively covers the studies on electrochemical materials for KIBs, including electrode and electrolyte materials and a discussion on recent achievements and remaining/emerging issues. The review also includes insights into electrode reactions and solid-state ionics and nonaqueous solution chemistry as well as perspectives on the research-based development of KIBs compared to those of LIBs and NIBs.

Research Development on K-Ion Batteries.

Carbohelicenes are a class of fascinating chiral helical molecules which have a rich history in chemistry. Over a period of almost 100 years, chemists have developed many methods to prepare them in a racemic or in a non-racemic form. They also possess a series of interesting chiral, physical, electronic and optical properties. However, their utilization in chemistry or chemistry-related fields has rarely appeared in a detailed and comprehensive review. It is the purpose of this review to collect fundamental applications and functions involving carbohelicenes in various disciplines such as in materials science, in nanoscience, in biological chemistry and in supramolecular chemistry. From the numerous synthetic methodologies reported up to now, carbohelicenes and their derivatives can be tailor-made for a better involvement in several subfields. Among those domains are: nanosciences, chemosensing, liquid crystals, molecular switches, polymers, foldamers, supramolecular materials, molecular recognition, conductive and opto-electronic materials, nonlinear optics, chirality studies and asymmetric synthesis. Helicene chemistry is now at a developmental stage, where sufficient application data are now collected and are extremely useful. They provide many more ideas for setting up the basis for future innovative applications.

One hundred years of helicene chemistry. Part 3: applications and properties of carbohelicenes

Thin zeolite films are attractive for a wide range of applications, including molecular sieve membranes, catalytic membrane reactors, permeation barriers, and low-dielectric-constant materials. Synthesis of thin zeolite films using high-aspect-ratio zeolite nanosheets is desirable because of the packing and processing advantages of the nanosheets over isotropic zeolite nanoparticles. Attempts to obtain a dispersed suspension of zeolite nanosheets via exfoliation of their lamellar precursors have been hampered because of their structure deterioration and morphological damage (fragmentation, curling, and aggregation). We demonstrated the synthesis and structure determination of highly crystalline nanosheets of zeolite frameworks MWW and MFI. The purity and morphological integrity of these nanosheets allow them to pack well on porous supports, facilitating the fabrication of molecular sieve membranes.

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Dispersible exfoliated zeolite nanosheets and their application as a selective membrane

The hydrothermal reaction of ZnUO2(OAc)4·7H2O with pyridine-2,3-dicarboxylic acid gives rise to a novel uranium−zinc−organic coordination polymer containing infinite U−O−Zn double sheets and organic ligands. Thermal and photoelectrochemical analyses indicate that the coordination polymeric compound not only has a high thermal stability but also exhibits interesting photoelectronic properties.

Synthesis, structure, and photoelectronic effects of a uranium-zinc-organic coordination polymer containing infinite metal oxide sheets.

The orthoferrite YFeO3 with orthorhombic perovskite structure (Pnma) has been synthesized by mild hydrothermal method. The temperature-dependent magnetization and hysteresis loops indicate that, due to the superexchange and Dzyaloshinskii-Moriya interactions in the crystals, the Fe spins order antiferromagnetically at the Neel temperature 655 K with a weak ferromagnetic moment. The observation of saturation polarization loops at room temperature and 77 K provide evidence for the ferroelectric character of the polycrystalline samples. Its Curie temperature has been obtained from the temperature dependence of the relative permittivities and thermal analysis. As a result, the structure exhibits simultaneously weak ferromagnetic and ferroelectric behavior.

The multiferroic perovskite YFeO3

Ni3S2 nanosheets doped with tin (Sn) grown on nickel foam (Sn–Ni3S2/NF) through a facile hydrothermal process were found to be superior water-splitting electrocatalysts. As for overall water splitting (OWS), when the current density is 10 mA cm–2, the required voltage is only 1.46 V. Meanwhile, it exhibits a large current density property and long-time stability (>60 h current–time tests) for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). In order to reach the current densities of 100 and 1000 mA cm–2, Sn–Ni3S2/NF needs overpotentials of 0.17 and 0.57 V for HER, and 0.27 and 0.58 V for OER, respectively. The water-splitting property of Sn–Ni3S2/NF is much better than that of pure Ni3S2/NF or even 20 wt % Pt/C/NF and RuO2/NF. Furthermore, Sn–Ni3S2/NF showed a higher turnover frequency at different potentials, with ∼100% Faraday efficiency for both O2 and H2. The improved activity of Sn–Ni3S2/NF activity for water-splitting is attributed to the doping of Sn, which enhanc...

Sn-Ni3S2 Ultrathin Nanosheets as Efficient Bifunctional Water-Splitting Catalysts with a Large Current Density and Low Overpotential.

A unique metal–organic polymer Mn·PDB·H2O (H2PDB = pyridine-3,4-dicarboxylic acid), with weak antiferromagnetic interactions both between the manganese(II) centers of an infinite Mn–O–C chain and between the adjacent chains, has been synthesized by the hydrothermal reaction of Mn(CH3COO)2·4H2O with H2PDB; X-ray diffraction shows that the polymer possesses a one-dimensional rectangular channel built up from pyridine rings and pseudo-layers formed by infinite straight Mn–O–C chain building units.

Assembly of a manganese(II) pyridine-3,4-dicarboxylate polymeric network based on infinite Mn–O–C chains

Bi1-xGdxFeO3 (x = 0, 0.1, 0.2, 0.3) nanoparticles were synthesized by polyol-mediated method. They show a compositional-driven phase transition from a rhombohedral phase (R3c) for x = 0 to an orthorhombic phase (Pn21a) for x = 0.2 and 0.3, and x = 0.1 is a mixture of both phases. Improved ferroelectric hysteresis loops are observed at room temperature for all samples with moderate polarization values. The substitution of Gd ions for Bi enhances the ferromagnetic properties of this system. A large saturated magnetization of 0.11 μB/f.u. is obtained at 300 K, which is mainly attributed to the antiferromagnetic core and ferromagnetic surface of the nanoparticles, together with the structural distortion. Temperature- and field-dependence of magnetization curves reveal the frustrated magnetic behavior of this system. The variation of magnetic behaviors at different reaction temperatures is also related to the competition between canted antiferromagnetic Fe sublattice and paramagnetic Gd sublattice.

Hongming Yuan

Papers

Synthesis, structure, and photoelectronic effects of a uranium-zinc-organic coordination polymer containing infinite metal oxide sheets.

The multiferroic perovskite YFeO3

Sn-Ni3S2 Ultrathin Nanosheets as Efficient Bifunctional Water-Splitting Catalysts with a Large Current Density and Low Overpotential.

Assembly of a manganese(II) pyridine-3,4-dicarboxylate polymeric network based on infinite Mn–O–C chains

Structure, Magnetic, and Ferroelectric Properties of Bi1-xGdxFeO3 Nanoparticles