Tailoring Coordination Microenvironment of Cu(I) in Metal–Organic Frameworks for Enhancing Electroreduction of CO2 to CH4

Abstract The coordination microenvironment of metal active sites in metal–organic frameworks (MOFs) plays a crucial role in its performance for electrochemical CO 2 reduction reaction (CO 2 RR). However, it remains a challenge to clarify the structure–performance relationship for CO 2 RR catalyzed by MOFs. Herein, a series of MOFs with different coordination microenvironments of Cu(I) sites (CuCl, CuBr, and CuI) to evaluate their performances for CO 2 RR is synthesized. With the increasing radius of halogen atom, the CO 2 adsorption capacity increases and d‐band center of Cu positively shifts to the Fermi level, leading to enhance the selectivity of CO 2 to CH 4 conversion. CuI gives the highest total Faradaic efficiency (FE) of 83.2%, with a FE of CH 4 up to 57.2% and CH 4 partial current density of 60.7 mA cm −2 at −1.08 V versus reversible hydrogen electrode. Theoretical calculations reveal that the shifted d‐band center of Cu site contributes to reduced formation energies of *CH 2 O and *CH 3 O intermediates, which is the potential‐determining step of CO 2 RR and thus facilitates the electrocatalytic CO 2 reduction to CH 4 . This study opens a new avenue for studying the relationship between the coordination microenvironment of active site and electroreduction reaction performance of MOFs.