Steering CO2 electroreduction to hydrocarbons over 2D thiol-based conductive metal-organic framework

Abstract

Almost all of Cu_xS compounds only produce the simple two-electron transferred products CO and HCOOH but it remains a large challenge to obtain the multiple-electron transferred hydrocarbon products in electrocatalytic CO₂ reduction reaction (CO₂RR). Moreover, identifying the distinct contributions of S atoms to catalysis, particularly for catalytic activity and product selectivity in electrocatalytic CO₂RR, remains a challenging task. Herein, we introduce a model catalyst based on a conductive two-dimensional metal-organic framework with defined Cu-S₄ active sites, named Cu₃(THT)₂ (THT = 2,3,6,7,10,11-hexathiotriphenylene) for CO₂RR. Unlike the precursor catalyst Cu₃(HITP)₂ with Cu-N₄ motifs that predominantly produce common two-electron transferred product CO (40% selectivity), Cu₃(THT)₂ shifts the primary product to deep reduction product CH₄. At −1.4 V versus the reversible hydrogen electrode (RHE), Cu₃(THT)₂ achieves a Faradaic efficiency of 63.5% for CH₄ and the current density reaches a high value of −298.3 mA cm⁻². Theoretical studies indicate that the electron-rich Cu-S₄ sites stabilize and activate the key intermediate *CO more effectively than Cu-N₄ sites. Furthermore, S atoms can accept electrons and form weak S···O interactions with *CO, providing additional stabilization for *CO. This study is the first to show that non-metallic S centers around catalytic metal sites can significantly enhance and tune product selectivity in CO₂RR.