Selectively Regulating Lewis Acid–Base Sites in Metal–Organic Frameworks for Achieving Turn‐On/Off of the Catalytic Activity in Different CO2Reactions

Abstract

AbstractRegulating Lewis acid–base sites in catalysts to investigate their influence in the chemical fixation of CO2is 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 that1can catalyze cycloaddition of CO2and aziridines to give 99 % yield. The efficiency of the cyclization of CO2with propargyl amines is only 32 %. To improve the catalytic ability of1, ligand XN with Lewis base sites was introduced into1and 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 MOF2({(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 from2treated with acid solution support this conclusion. This work illuminates a MOF‐construction strategy that produces efficient catalysts for CO2conversion.