A Light-Switchable Polyoxometalate "Electron Pump" in a One-Dimensional Copper Coordination Polymer: Near-Unity...

Photocatalytic CO₂ reduction to methane (CH₄) is highly desirable but severely hindered by sluggish multiple proton-coupled electron transfer (MPCET) kinetics and poor product selectivity. In this study, we report a novel one-dimensional (1D) copper coordination polymer, termed Cu-PMo₁₂, featuring single-site Cu centers periodically bridged by Keggin-type {PMo₁₂} clusters. Comprehensive experimental and theoretical studies reveal a synergistic mechanism governed by static electronic modulation and dynamic photoactivation. In the ground state, {PMo₁₂} acts as an electron acceptor, withdrawing electrons from Cu sites to upshift the Cu d-band center, thereby strengthening the binding affinity toward intermediates. Under visible-light irradiation, {PMo₁₂} functions as a photosensitizer and a light-switchable "electron pump", directionally injecting photogenerated electrons to Cu sites to dynamically maintain highly active Cu(I) species for the subsequent MPCET process. Consequently, Cu-PMo₁₂ achieves an exceptional CH₄ evolution rate of 70.5 µmol g_Cu ^{- 1} h^{- 1} with near-unity selectivity (∼100%) and excellent durability. This work highlights precise microenvironment engineering via polyoxometalate-metal integration and provides a paradigm for designing light-driven "electron pump" systems for challenging multi-electron catalytic transformations.