Induced CO2 Electroreduction to Formic Acid on Metal-Organic Frameworks via Node Doping

Abstract

Metal-organic frameworks (MOFs), combining the advantages of heterogeneous and homogeneous components, have been explored as catalytic materials for the CO₂ electroreduction reaction (CO₂ ERR). However, the unmatched metal nodes result in MOFs having lower faradaic efficiencies (FEs) and limited current densities in CO₂ ERR. Herein, we report a general strategy to promote activities of MOFs via node doping in CO₂ ERR. With ion exchange, an active tin node was doped into zeolitic imidazolate framework-8 (ZIF-8) to facilitate the reduction kinetics of CO₂ . The divalent Sn²⁺ node accelerates the formation of formic acid (HCOOH), resulting in the highest HCOOH FE of 74 % and total current density (J_total ) of 27 mA/cm² at -1.1 V (vs. reversible hydrogen electrode, RHE) over 0.6 wt% Sn-doped ZIF-8 with stable catalytic performance after seven reuse cycles, which is clearly better compared to the catalytic properties of pristine ZIF-8 (FE_HCOOH =0 %, J_total =13 mA/cm² ). This work opens an avenue for promoting the CO₂ ERR performance of MOFs by node doping.

Keywords: CO2 electroreduction; Formic acid; MOF; Node doping.