Integrating Suitable Linkage of Covalent Organic Frameworks into Covalently Bridged Inorganic/Organic Hybrids toward Efficient Photocatalysis.

Covalent organic frameworks (COFs) are excellent platforms with tailored functionalities in photocatalysis. There are still challenges in increasing photochemical performance of COFs. Therefore, we designed and prepared a series of COFs for photocatalytic hydrogen generation. Varying different ratios of β-ketoenamine to imine moieties in the linkages could differ the ordered structure, visible light harvesting and bandgap. Overall β-ketoenamine linked-COFs exhibited much better photocatalytic activity than those COFs having both β-ketoenamine and imine moieties on account of non-quenched excited-state and more favorable HOMO level in photoinduced oxidation reaction from the former. Specifically, after in situ growth of β-ketoenamine linked COFs onto NH2-Ti3C2Tx (Tx = -O and -OH) MXene via covalent connection, the hetero-hybrid showed an obvious improvement in photocatalytic H2 evolution because of strong covalent coupling, electrical conductivity and efficient charge transfer. This integrated linkage evolution and covalent hybridization approach advances the development of COF-based photocatalysts.