3D Covalent Arsenic Polyoxomolybdate‐Organic Polymer with Ultrahigh Photocatalytic Oxidative Ability for Aromatic C─H Activation

Abstract The photocatalytic activation of inert aromatic C─H bonds under mild conditions remains a major challenge due to the inherent stability of sp 2 C─H bonds and the lack of efficient, selective heterogeneous photocatalysts. Herein, by strategically balancing the solubility of aniline‐functionalized arsenic polyoxomolybdate (AsPOM) with the organic linker of 1,4‐bi(3‐dimethylamino‐1‐oxoprop‐2‐enyl)benzene (BDOEB), a new 3D covalent AsPOM‐organic polymer, termed POF‐2, was successfully prepared. Its short‐ to medium‐range ordered structure was resolved using the advanced total scattering atomic pair distribution function (PDF). The unique architecture of POF‐2 synergistically combines the strong oxidative capability of AsPOM with the tunable light absorption and oxygen activation ability of organic monomers, narrowing the bandgap from 3.13 eV (AsPOM) to 2.28 eV (POF‐2) and extending light absorption to 575 nm. Under ambient conditions with low‐energy visible‐light irradiation (10 W LED), POF‐2 exhibits exceptional photocatalytic performance in aromatic C─H bromination and [3+2] cycloaddition reactions, achieving >99% conversion and >99% selectivity. Mechanistic studies reveal that the well‐defined donor–acceptor (D–A) structure of POF‐2 facilitates rapid hole (h + )‐mediated C─H activation on AsPOM nodes and selective 1 O 2 generation on BDOEB linkers, avoiding nonproductive substrate mineralization. This work not only demonstrates a new 3D covalent AsPOM‐organic polymer for C─H functionalization but also provides a blueprint for designing molecularly precise, multifunctional photocatalysts for sustainable organic synthesis.