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

Abstract

ABSTRACT 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 Mn 2+ ions (3d 5 , half‐filled configuration) into a chemically robust sp 2 ‐carbon‐linked COF (sp 2 c‐COF dpy ). The resulting sp 2 c‐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 d 5 configuration of Mn 2+ 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.