A Light‐Switchable Polyoxometalate “Electron Pump” in a One‐Dimensional Copper Coordination Polymer: Near‐Unity Selective CO ₂ Photoreduction to Methane

Photocatalytic CO 2 reduction to methane (CH 4 ) 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‐PMo 12 , featuring single‐site Cu centers periodically bridged by Keggin‐type {PMo 12 } clusters. Comprehensive experimental and theoretical studies reveal a synergistic mechanism governed by static electronic modulation and dynamic photoactivation. In the ground state, {PMo 12 } 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, {PMo 12 } 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‐PMo 12 achieves an exceptional CH 4 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.