Boosting photocatalytic hydrogen evolution enabled by SiO2-supporting chiral covalent organic frameworks with parallel stacking sequence

Two-dimensional covalent organic frameworks (2D COFs) feature extended π-conjugation and ordered stacking sequence, showing great promise for high-performance photocatalysis. Periodic atomic frameworks of 2D COFs facilitate the in-plane photogenerated charge transfer, but the precise ordered alignment is limited due to the non-covalent π-stacking of COF layers, accordingly hindering out-of-plane transfer kinetics. Herein, we address a chiral induction method to construct a parallelly superimposed stacking chiral COF ultrathin shell on the support of SiO2 microsphere. Compared to the achiral COF analogues, the chiral COF shell with the parallel AA-stacking structure is more conducive to enhance the built-in electric field and accumulates photogenerated electrons for the rapid migration, thereby affording superior photocatalytic performance in hydrogen evolution from water splitting. Taking the simplest ketoenamine-linked chiral COF as a shell of SiO2 particle, the resulting composite exhibits an impressive hydrogen evolution rate of 107.1 mmol g–1 h–1 along with the apparent quantum efficiency of 14.31% at 475 nm. Furthermore, the composite photocatalysts could be fabricated into a film device, displaying a remarkable photocatalytic performance of 178.0 mmol m–2 h–1 for hydrogen evolution. Our work underpins the surface engineering of organic photocatalysts and illustrates the significance of COF stacking structures in regulating electronic properties.