Covalent Organic Framework Coupled with Atomically Precise Copper Nanoclusters for Efficient Tandem Electroreduction Reaction of CO₂.

Abstract

The electrocatalytic reduction of CO₂ (CO₂RR) presents a viable approach to reduce CO₂ emissions and generate valuable chemicals. However, selectivity toward highly valuable C₂₊ products is still insufficient for practical applications. Herein, we propose an efficient tandem catalytic strategy to polish up the performance of C₂₊ products via adjacent distinct catalytic sites. The tandem electrocatalyst Cu/NiPc-COF is constructed by uniformly dispersing atomically precise copper nanoclusters [Cu₃₂(PET)₂₄H₈Cl₂](PPh₄)₂ (PET = 2-phenylethanethiolate), denoted as Cu₃₂ NCs, on the two-dimensionally conductive Ni-phthalocyanine-based covalent organic framework (NiPc-COF). A high selectivity of 57.1% for C₂₊ products (C₂H₄, CH₃COOH, and C₂H₅OH) and a total current density of 353.3 mA cm^-2 is reached at -1.6 V in aqueous electrolyte, which surpasses the corresponding Cu₃₂ NCs (FE_C₂₊ = 24.4%, <i>j</i>_total = 250.1 mA cm^-2, -1.6 V) and some other electrocatalysts. Operando experiments and DFT calculations show that locally high *CO concentrations from NiPc-COF sites cause a massive *CO spillover to Cu₃₂ NCs. This enriches *CO coverage, boosting the selectivity of C₂₊. The work provides an effective approach for designing tandem electrocatalysts that achieve high selectivity to C₂₊.