Helicalization of Covalent Organic Framework Nanofibers with Amplified Spin Polarizability for Boosting Photocatalytic Hydrogen Evolution

Given that chirality can induce spin polarization via the chirality-induced spin selectivity (CISS) effect, integrating conformational chirality into covalent organic frameworks (COFs) can offer a route to harness CISS for long-range spin-polarized charge transfer in crystalline materials. However, achieving both high crystallinity and strong chirality in COFs remains challenging. Here, we report a noncovalent chirality transfer strategy to modulate helical assembly of 2D COF nanofibers from achiral building blocks. The chiral solvent (R/S)-3-chloro-1,2-propanediol triggers a stacking deviation of bipyridine modules via hydrogen bonding and halogen bonding, leading to chirality transfer and steering helical growth. The resulting COF features global conformational chirality, helically intertwined morphology and high crystallinity. In photocatalytic hydrogen evolution, the helical COF achieves a H₂ production rate of 44 mmol g^-1 h^-1 with the quantum efficiency of 7.18% at 500 nm, markedly outperforming achiral and weakly chiral analogues. The superior performance originates from the helical structure, which induces exceptional spin polarization (74%-88%) via CISS, thereby enhancing exciton dissociation and extending carrier lifetime. This work establishes a strategy of noncovalently directed helical crystallization of 2D COFs and demonstrates that rendering organic semiconductors helicity can amplify spin polarization to enhance intrinsic photocatalytic activity, offering a design pathway for advanced photocatalysts.