Selectively Regulating Lewis Acid-Base Sites in Metal-Organic Frameworks for Achieving Turn-On/Off of the Catalytic Activity in Different CO2 Reactions

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)[Co-3(mu(3)-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)[Co-3(mu(3)-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.

Automated summary

This study investigates the influence of Lewis acid-base sites in catalysts on the chemical fixation of CO2. It demonstrates that with the introduction of Lewis base sites, the catalytic ability of a metal-organic framework (MOF) is improved, leading to enhanced efficiency in the conversion of CO2.