Radiation-Powered Catalytic Alchemy: 3e– Reduction of Perrhenate via Confined Active Sites in Covalent Organic Framework Nanoreactors

The catalytic reduction of high-valent metal oxysalts to their low-valent counterparts represents a pivotal route for environmental remediation and sustainable resource recovery. However, the inherently low redox potentials of certain oxysalts, exemplified by perrhenate (ReO₄^–), pose a persistent challenge for conventional reduction strategies. Herein, we report a rationally designed π-conjugated olefin-linked covalent organic framework (COF) catalyst, which incorporates isolated transition metal centers (M = Ni or Cu) to facilitate the γ-ray-powered catalytic reduction of ReO₄^–. Through synergistic spatial confinement and electronic modulation, the catalyst enables near-quantitative selectivity toward ReO₂ production via a unique three-electron (3e^–) transfer pathway, overcoming the bottleneck of multielectron reduction. The energy efficiency of the reduction reaches up to 42.1 mmol MJ^–1. Synergistic experimental and theoretical investigations reveal that radiation-generated hydrated electrons (e_aq^–) participate in a coordination-electron relay process, involving a critical μ-oxo double-bridged [M–O(O)–Re] intermediate. Remarkably, the conjugated COF demonstrates superior radiation resistance, retaining crystallinity and porosity after prolonged irradiation. This work establishes a new paradigm for harnessing COFs as robust platforms for heterogeneous radiation catalysis, with potential applications in the treatment of redox-recalcitrant pollutants.