Intermingled Coordination Environments Enable Defect‐Engineered Metal–Polyphenol/G‐Quadruplex Hydrogel for Enhanced N ₂ ‐to‐NH ₃ Photoconversion

Manipulating the coordination environment through hetero-ligand incorporation induces controlled defects at catalytically active sites, offering a powerful route to regulate electronic structure and reactivity. Here, we present a supramolecular approach to defect engineering within a soft hydrogel matrix by confining a Bi³⁺-caffeic acid complex within a guanosine monophosphate-based G-quadruplex hydrogel. This confinement not only breaks local coordination symmetry and generates oxygen-vacancy-rich heterojunctions but also emulates the active-site environments of enzymes. The G-quadruplex fibrillar scaffold provides ion-channel-like pathways that facilitate charge transport, enhance substrate diffusion, and promote selective adsorption, while confinement ensures the uniform dispersion of catalytic sites. Together, these synergistic effects result in an exceptional N₂ to NH₃ conversion of 905.2 µmol h^-1 g^-1 _(cat) under visible light irradiation, 3.8 times higher than that of the pristine complex. This work introduces a versatile strategy that integrates defect engineering, heterojunction formation, and biomimetic confinement within a soft supramolecular assembly, establishing G-quadruplex hydrogels as a powerful platform for sustainable photocatalytic nitrogen fixation and beyond.