Tuning the Pore Microenvironment of Metal-Organic Frameworks for Boosting CO2 Fixation.

The pore microenvironment plays an important role in catalytic systems, as it can regulate substrate transport, reactant molecule enrichment, and the strength of active centers, thereby affecting catalytic performance. However, the effect of pore sizes/functionality/Lewis acid strength on catalytic performance has still not been adequately and systematically investigated and summarized. Herein, a series of isostructural fcu-type metal-organic frameworks (MOFs) are used through a novel strategy to study the effect of subtle changes in pore microenvironment on the catalysis of carbon dioxide (CO2) cycloaddition at ambient temperature and pressure. The results of systematic experiments indicate that the enlargement of the pore size of MOFs, the access of pore wall functional groups, and the increase of Lewis acid strength of metal nodes can significantly improve the performance of the CO2 cycloaddition reaction. The reaction mechanism catalyzed by fcu-type MOFs is investigated in detail, based on the experimental inferences and periodic calculations of density functional theory. This study provides a reference for designing of high-performance catalysts for CO2 fixation.