Promoted CO2 photoreduction toward HCOOH generation by nucleophilic effect in Co/Mg synergistic catalysis

Abstract

The photoreduction of carbon dioxide (CO2) into a valuable energy is one of the most promising strategies for the current global climate crisis. The synergistic catalysis of bimetallic Metal-organic frameworks (MOFs) has shown considerable potential in photocatalytic reduction of CO2, how to design an efficient catalytic active center is still a thorny problem. Here, bimetallic MOF, CoMg-TCPP, was successfully prepared by post-synthetic exchange method. Under visible light, CoMg-TCPP can be the efficient catalyst for CO2 reduction with the yields of gas product (CO) and liquid product (HCOOH) up to 14.34 mmol g−1 h−1 and 0.94 mmol g−1 h−1, respectively. Of note, the synergistic effect between the bimetals in CoMg-TCPP enables formic acid yield is more than twice that of monometallic counterpart Co-TCPP. Theoretical calculations show that the introduction of the second metal regulates the electronic structure of the intermediates which reduces the formation energy barrier of Co-O-COH intermediates and significantly promotes the formation of Co-HCOOH, thus obtaining efficient HCOOH generation performance. Moreover, the addition of Mg to Co-TCPP enhances the nucleophilicity of the Co center and makes it more inclined to interact with O-COH groups. This work provides further insights into the mechanisms of CO2 photocatalytic reduction based on the bimetal-organic framework.