Vinylene-linked covalent organic frameworks based on phenanthroline for visible-light-driven bifunctional photocatalytic water splitting

• Two phenanthroline-based vinylene-linked COFs were reported for the first time. • The first application of phenanthroline-based COFs for water splitting. • The proton reduction and water oxidation activities surpass most bifunctional COFs. • High π-conjugation and strong chelating promote charge transfer/catalytic reaction. Covalent organic frameworks (COFs) are one type of good platforms for photocatalysis, but conflating three keys (light absorption, charge separation and catalytic conversion) of photocatalysis all in one photocatalyst for efficient photocatalytic water splitting remains challenging. Herein, we employ phenanthroline , the two nitrogen atoms of which have strong complexation competence to anchor metal cocatalysts, and trigonaldehydes to synthesize novel vinylene-linked COFs (PVCOFs) through the Aldol condensation reaction. PVCOFs exhibit wide visible light absorption capacity with absorption band edge at above 600 nm, and the optimized H 2 and O 2 evolution rates of PVCOF-1 are as high as 11,525 and 2056 μmol g −1 h −1 , respectively, which are much higher than those of the reported dual-functional COFs-based photocatalysts. The promising photocatalytic performance is attributed to high π-conjugation of vinylene linkage, which results in strong electron delocalization and eminent charge separation efficiency. The strong complexation competence of the nitrogen atoms in phenanthroline can anchor metal cocatalyst, permit efficient charge transfer in the COF/cocatalyst interfaces, and hasten catalytic conversion, thus improving the catalytic conversion efficiency and endowing phenanthroline-based COFs for photocatalytic water splitting for the first time. This work sheds new light on the vinylene-linked COFs photocatalysts for solar-to-chemical conversion.