Synergistic effect between boron containing metal-organic frameworks and light leading to enhanced CO2 cycloaddition with epoxides

Abstract

Cycloaddition between CO2 and epoxides to produce cyclic carbonates is a promising approach to reach carbon neutralization. In this work, a boron-containing zirconium based metal–organic framework (UiO-67-B) possessing the same topological structure with UiO-67 was prepared by replacing biphenyl-4,4′-dicarboxylic acid with 4′-borono-[1,1′-biphenyl]-4-carboxylic acid. UiO-67-B exhibits efficient activity towards the CO2 cycloaddition reaction under ambient conditions and light irradiation. Various characterizations suggest that the boron in UiO-67-B and light display synergistic effect on improving the activity. Specifically, (1) UiO-67-B displays extended light absorption; (2) UiO-67-B exhibits enhanced ligand to metal charge transfer (LMCT) process upon light irradiation; and (3) the presence of boron provides sites for the chemical adsorption and the subsequent activation of CO2, which avoids the competition with epoxide adsorption onto zirconium. This study illustrates the combination of boron and light in promoting the CO2 cycloaddition reaction, and provides a new strategy for designing efficient catalysts towards CO2 capture and conversion under mild conditions.