Chiralizing Covalent Organic Frameworks to Boost H₂O₂ Photosynthesis

Solar-driven H₂O₂ photosynthesis offers a sustainable route to on-site oxidant production, yet the selective reduction of triplet O₂ to spin-paired H₂O₂ remains kinetically challenging. Covalent organic framework (COF) photocatalysts have largely focused on charge separation and active-site reactivity, while overlooking the spin character of electrons transferred to O₂. Here we discover that chiralization renders COFs significantly enhanced production of H₂O₂, and report a chiralization strategy for spin-regulated H₂O₂ photosynthesis in β-ketoenamine-linked COFs. The chiral frameworks enable spin-selective electron transport, favor the O-O-bond-preserving reduction pathway and lower the apparent kinetic barrier for H₂O₂ formation. Chiralization enhances H₂O₂ production by 38.7%-252.1% relative to achiral counterparts. A bipyridine-containing chiral COF reaches 22.8 mmol g^-1 h^-1 using solely water and oxygen, with an apparent quantum yield of 10.3% at 420 nm, placing it at the forefront of sacrificial-agent-free COF systems. Membrane-integrated chiral COFs enable continuous-flow H₂O₂ production. These findings establish chirality as a design parameter coupling spin-selective electron transport with O₂ reduction pathway control, opening new directions for COF photocatalysis.