Polarized π-Spacer Engineering Enables Sequential Electron Transfer for Photocatalytic Water Splitting in Covalent Organic Frameworks

Covalent organic frameworks (COFs) have significant potential for solar-driven water splitting, yet they face the critical challenge of suppressing rapid charge recombination. Herein, we demonstrate a linker engineering strategy for the construction of COFs that involves polarized π-spacers to integrate donor and acceptor units into anisotropic skeletons. Under illumination, the polarized π-spacers induce an intramolecular sequential electron transfer along the linkers, enabling an enhanced charge delocalization and thereby significantly prolonging the charge-separated states compared to the binary-component counterparts. As a result, the designed ternary-ordered COF shows enhanced co-production of H2 and H2O2 from visible-light-driven water splitting, achieving an apparent quantum efficiency of 0.98% at 420 nm, outperforming most reported analogous materials. This strategy of driving sequential electron transfer in COFs by linker design to suppress charge recombination offers a rational approach for developing high-performance photocatalytic systems.