High-efficiency photodriven coupling of CO2 and various epoxides via multi-shelled hollow ZIF/MXene derived composite with low activation energy

Abstract

Photo-induced carbon dioxide (CO2) conversion is a promising pathway to synthesize value-added chemicals in a sustainable manner, but the process is usually hampered by the high activation energy, low light harvesting capability, and the fast recombination of charge carriers. Herein, cobalt nanoparticles encapsulated in N-doped hierarchically porous carbon/TiO2/MXene (CoNHPC/TM) composites were synthesized by high temperature pyrolysis, employing a multilayer ZIF-8@ZIF-67@ZIF-8@ZIF-67 (4L-ZIF)/MXene hybrid as a precursor. During the pyrolysis process, the multilayer 4L-ZIF solid was transformed into CoNHPC with a multi-shell hollow structure, while TiO2 nanoparticles formed in situ on the MXene surface. This unique structure induces multiple reflections of internal light, thus increasing the efficiency of light energy harvesting and photothermal conversion, as well as significantly improving mass diffusion and the separation efficiency of photogenerated carriers. Consequently, a 96% yield for cyclic carbonate was achieved by the optimal CoNHPC/TM-8 (initial mass ratio of 4L-ZIF to MXene: 8:1) under irradiation of full spectrum light at 350 mW/cm2 for 6 h. Additionally, its high catalytic efficiency was maintained even under simulated flue gas conditions. Further investigations revealed a decrease in the activation energy and a synergistic photocatalytic-photothermal effect in the reaction systems with CoNHPC/TM-8. Our research provides inspiration for the rational design of MOF-based photocatalysts with desirable practical applicability for enhancing CO2 transformation.