Au Nanoparticles Encapsulated in Metal−Organic Framework for Enhanced Carbon Dioxide Reduction

Abstract

The direct deployment of metal−organic framework (MOF) as an electrocatalyst for CO₂ reduction is often hampered by their intrinsically poor conductivity, the adsorption−desorption trade-off in intermediate binding energetics, and limited formation of multi-carbon products. To address these challenges, gold nanoparticles (Au NPs) were encapsulated within reconstructed nanowire-like structures derived from a copper-based 1,4-benzenedicarboxylate framework (CuBDC) via an in situ reduction strategy, forming an Au/CuBDC-4 composite. Despite the resulting structural disordering and partial copper loss, the optimized catalyst achieved a notable Faradaic efficiency of 60% for ethylene (C₂H₄) and 73% for C₂₊ at −0.8 V vs RHE, along with a significantly suppressed hydrogen evolution reaction (HER). Electrochemical analyses reveal increased C_dl and reduced charge-transfer resistance and a lower Tafel slope, indicating improved interfacial accessibility and charge-transfer kinetics. In situ Raman spectroscopy identifies potential-dependent vibrational bands associated with metal−CO-related and CO-derived surface species, suggesting the formation of reaction-induced intermediates under CO₂RR conditions. When combined with density functional theory (DFT) calculations, the cooperative roles of Au and Cu sites at the Au/CuBDC-n interface are further supported. Au sites may facilitate *CO formation and increase local *CO availability adjacent to Cu sites, while the same Cu sites provide favorable sites for C−C coupling with a lower calculated free-energy requirement. The resulting interfacial cooperation, together with increased catalytic-interface accessibility, facilitated interfacial charge transport and more efficient utilization of Cu sites, thereby promoting C₂H₄ formation. This work offers insights into the rational design of MOF-based synergistic catalysts with high selectivity and low overpotential for efficient CO₂ valorization.