High Spin Manganese Boosting Photo-Magnetic Catalytic Hydrogen Evolution Over Covalent Organic Frameworks

Harnessing electron spin to suppress photogenerated carrier recombination represents a relatively underexplored frontier in photocatalytic hydrogen evolution. However, conventional photocatalysts are predominantly diamagnetic and respond weakly to external magnetic fields, limiting the exploitation of spin-dependent carrier dynamics. Here, we report for the first time the application of covalent organic frameworks (COFs) in photo-magnetic coupled hydrogen evolution. Specifically, a post-synthetic metalation strategy is developed to introduce high-spin Mn²⁺ ions (3d⁵, half-filled configuration) into a chemically robust sp²-carbon-linked COF (sp²c-COF_dpy). The resulting sp²c-COF_dpy-Mn exhibits intrinsic spin polarization with an unprecedented 100% spin polarization degree at the Fermi level, as revealed by density functional theory calculations. Under an external magnetic field of 500 mT, the material achieves a record photocatalytic hydrogen evolution rate of 208.48 mmol·g^-1·h^-1. Combined experimental and theoretical analyses demonstrate that the half-filled d⁵ configuration of Mn²⁺ maximizes unpaired electrons, inducing strong spin polarization and a large magnetic moment. The external magnetic field further activates negative magnetoresistance and spin-flip processes, synergistically suppressing electron-hole recombination and accelerating interfacial charge transfer to Pt cocatalyst sites. This work not only establishes the first example of COFs in photo-magnetic catalytic hydrogen evolution but also provides a general spin-engineering strategy for designing high-performance magnetically responsive photocatalysts.