Regulating Lewis acid–base sites in catalysts to investigate their influence in the chemical fixation of CO2 is significant but challenging. A metal–organic framework (MOF) with open metal Co sites, {(NH2Me2)[Co3(μ3‐OH)(BTB)2(H2O)]⋅9 H2O⋅5 DMF}n (1), was obtained and the results of the catalytic investigation show that 1 can catalyze cycloaddition of CO2 and aziridines to give 99 % yield. The efficiency of the cyclization of CO2 with propargyl amines is only 32 %. To improve the catalytic ability of 1, ligand XN with Lewis base sites was introduced into 1 and coordinated with the open Co sites, resulting in a decrease of the Lewis acid sites and an increase in the Lewis base sites in a related MOF 2 ({(NH2Me2)[Co3(μ3‐OH)(NHMe2)(BTB)2(XN)]⋅8 H2O⋅4 DMF}n). Selective regulation of the type of active centers causes the yield of oxazolidinones to be enhanced by about 2.4 times, suggesting that this strategy can turn on/off the catalytic activity for different reactions. The catalytic results from 2 treated with acid solution support this conclusion. This work illuminates a MOF‐construction strategy that produces efficient catalysts for CO2 conversion.

On the basis of the global warming effect, it is of great significance to convert CO2 into the high value-added products oxazolidinones, but investigations on main-group-based metal–organic frameworks (MOFs) as heterogeneous catalysts still have not been reported so far. In this work, a quadruple-interpenetrated porous indium-based MOF, {[NH2(CH3)2]­[In­(CPT)2]·3CH3CN·3DMA} n (1), is constructed from the organic ligand 3,5-bis­(4′-carboxyphenyl)-1,2,4-triazole through solvothermal reactions, and N2 adsorption proves that the framework has a high Brunauer–Emmett–Teller surface areas with 2024 m2/g. The catalytic research on CO2 conversion reveals that compound 1 has high reactivity for the cycloaddition of CO2 with aziridines, and the product 3-ethyl-5-phenyloxazolidin-2-one can be obtained with a yield of 99% under mild conditions. In addition, 1 exhibits excellent activity for different kinds of substrates and can be reused at least five cycles without any significant deactivation, suggesting that 1 is a potential candidate for the chemical conversion of CO2 and aziridines. Mechanistic explorations indicate that the high efficiency of 1 is attributed to the indium center in the framework as a Lewis acid site, and the large porosity can enrich substrates. Importantly, 1 behaved as the first main-group MOF-based catalyst in the reported coupling reaction of CO2 with aziridines.

Hourglass-type polyoxometalate-based crystalline materials exhibit efficient photocatalytic activities towards simultaneous photocatalytic Cr(vi) reduction and organic MB oxidation.

Three hybrid phosphomolybdates were successfully synthesized by hydrothermal method and characterized by a series of physicochemical analysis techniques. X-ray single-crystal structural analysis revealed that three compounds with the reductive polyanionic clusters (Mo) were wrapped by protonated organic component bpp cations (bpp = 1,3-bi(4-pyridyl)propane) through the complex supramolecular hydrogen bonding network. They also have similar molecular formulas: (Hbpp)[PbM(HO)]H{M[MoO(OH)(HPO)(PO)]}· nHO (M = Fe in 1, Zn in 2, n = 4; or M = Mn in 3, n = 6). The oxidation states of all Mo centers in these polyanions are in the form of +5, presenting clusters with the higher negative charge. The feature showed that they were easy to be modified by transition metal and organic moieties, so as to form a high-dimensional structure and produce functional materials with specific properties. Comparison of catalytic ability of three crystals to reduce Cr using formic acid as reductant, found that crystal 1 was effectively active to this redox reaction. The conversion of Cr can reach 99% after 120 min of heating in 55 °C water bath, and the conversion of above 95% can still be achieved after 5 recycles of applications.

New Na-bridged phosphomolybdates as heterogeneous catalysts exhibit efficient catalytic performance on the reduction of hexavalent chromium and photodegradation of methylene blue.