Covalent Confinement of AuCu Nanoclusters in Metal‐Organic Frameworks for Photocatalytic CO 2 Reduction to C 2 Hydrocarbons

ABSTRACT Bimetallic alloy nanoclusters provide an ideal platform for photocatalytic CO 2 reduction owing to their synergistic, charge‐polarized electronic effects that facilitate C─C coupling. However, their application is hindered by three major challenges: poor stability associated with their ultrasmall size, difficulty in precise multi‐metal composition control, and the lack of universal ligand‐anchoring strategies. Herein, we report the first family of covalently stabilized, composition‐tunable AuCu alloy nanoclusters confined within an N‐heterocyclic carbene (NHC)‐functionalized metal‐organic framework (MOF, UiO‐68‐NHC‐Au x Cu 10‐x , 4 ≤ x ≤ 10) via robust metal‐NHC covalent bonds. The porous framework spatially confines ∼2 nm alloy nanoclusters to prevent aggregation while enabling precise modulation of the Au:Cu composition. Among the series, UiO‐68‐NHC‐Au 4 Cu 6 exhibits the highest photocatalytic performance, achieving a C 2 hydrocarbon evolution rate of 42.5 µmol g −1 h −1 with a C 2 selectivity of 77% (electron‐based), outperforming the vast majority of MOF/metal heterojunction and metal nanocluster‐based photocatalysts. In situ spectroscopic investigations and computational studies reveal that the synergistic Au─Cu sites promote C─C coupling via the formation of *COCOH intermediates, a pathway that is thermodynamically unfavorable over monometallic Au─Au sites. This work establishes a robust strategy for constructing MOF‐confined bimetallic nanoclusters with synergistic active sites, achieving efficient and selective CO 2 photoreduction to high‐value multi‐carbon products.