Defect-engineered MOF-801 for cycloaddition of CO2 with epoxides

Heterogeneous catalysts based on defective metal-organic frameworks (MOFs) have attracted wide attention due to their facile formation of defects during synthesis. Herein, two MOFs, MOF-801(D) and MOF-801(P), were synthesized by a solvothermal method using a modulation approach. The synthesized MOFs were characterized by using PXRD, N-2 BET, TGA, NH3 and CO2-TPD, CO2 adsorption isotherms, XPS, FT-IR, FE-SEM, and HR-TEM. A computational characterization method was developed to approximate the degree of defects using a combination of molecular simulation and a linear programming approach. Master isotherm models for N-2 isotherms at 77 K were constructed to match the experimental isotherm data of MOF-801(D) and MOF-801(P), and the pore size distribution and the degree of defects were quantified based on the predicted N-2 isotherms at 77 K. MOF-801(D) showed a high conversion of epoxide with >99% selectivity toward cyclic carbonate and 92% conversion under mild and solvent-less reaction conditions. MOF-801(D) was easily separated using a centrifuge and can be recycled up to 5 times without any significant decrease in its initial performance. Density functional theory (DFT) calculations were carried out to corroborate that the increased acid sites, from the cluster defects, are responsible for the increased catalytic conversion of the catalyst.

Automated summary

Heterogeneous catalysts based on defective metal-organic frameworks (MOFs) have been synthesized and characterized in this study. The synthesized MOFs were analyzed using various techniques, and a computational method was developed to approximate the degree of defects. One of the MOFs showed high catalytic conversion and selectivity, and it could be recycled multiple times.