Confinement of halide ions in Mg-Beta zeolites enables synergistic catalysis for CO2 cycloaddition

Abstract

The confinement of metal-based matrix such as clusters, particles and even isolated single atoms in zeolite framework was intensively reported, while it was highly untoward to realize this goal for non-metallic ions due to the mutually-exclusive electrostatic interaction between the zeolite framework with negative charges and non-metallic anions. Herein, confinement of iodide ions in Mg-Beta zeolites (I@Mg-Beta) was successfully accomplished via the methodology of structural reconstruction, whose physicochemical property, channel connectivity as well as the location of Mg2+ and I- ions were investigated systematically. It was found that Mg2+ ions were located in the zeolitic framework and I- ions were mainly confined in Mg-Beta zeolite via the electrostatic interaction with tetraethylammonium cations. The establishment of structure–function relationship in CO2 cycloaddition reaction with epoxides indicated the presence of synergistic effect between framework Mg2+ ions and confined I- ions. The immobilisation of halide ions onto a zeolite support enabled it the recoverable ability from reaction systems, giving rise to relatively stable reusability. The catalytic transformation of CO2 cycloaddition with epoxides in this work was devoted to ameliorate environmental stress from anthropogenic greenhouse gases of CO2 by means of elaborately constructing metallosilicate zeolite confined non-metallic catalysts with dual functions.