Nanoparticle-Single-Atom Tandem Catalyst within a Metal–Organic Framework for Efficient Ethylene Electrosynthesis

Copper nanoparticles (Cu NPs) are effective catalysts for the electroreduction of CO 2 (ECO 2 R) to multicarbon products but suffer from insufficient selectivity, aggregation, and deactivation. To address these challenges, we developed an in situ encapsulation strategy that engineers Cu NPs in a metal–organic framework (MOF) host from a simple one-pot hydrothermal synthesis, creating a selective and robust CO 2 R catalyst. The key design is the introduction of Sn additives during synthesis, which later evolve into single atoms (SAs) that serve a dual function: modulating the growth of Cu NPs from 3.35 to 9 nm and acting as active sites for the conversion of CO 2 to CO. The locally generated CO then feeds adjacent Cu NPs, promoting subsequent C–C coupling via a tandem mechanism. The optimal catalyst, with a balanced Cu/Sn ratio, achieves a CO 2 -to-C 2 H 4 Faradaic efficiency (FE) of 64%. Combined theoretical simulations and in situ infrared spectroscopy further reveal that Sn SAs promote Cu NPs electron transfer, enriching the electron density at active sites. This stabilizes *CO intermediates and reduces the energy barriers for CO 2 activation and ensuing C–C coupling steps. This work presents a novel atomic- and nanoscale design strategy for advanced CO 2 RR catalysts.