Alkene-Bridged Ionic Covalent Organic Nanosheets (iCONs) Based on D-π-A for Photocatalytic Hydrogen Evolution

Hydrophilicity, dispersivity, and charge-carrier separation are major factors that vitally affect photocatalytic hydrogen evolution (PHE). However, there has been relatively little research on considering these factors simultaneously. In this work, a series of 2D sp2 carbon-linked ionic covalent organic nanosheets (iCON-(1–4)) based on the D-π-A structure are designed and synthesized. iCONs with an ionic nature and ultrathin layered structures greatly promote their hydrophilicity and dispersivity as photocatalysts in catalytic systems and offer numerous interfaces as reaction sites for electron–hole separation. Furthermore, the ultrathin nanosheets possess the advantage of being beneficial to Pt loading apart from facilitating the utilization of surface-active sites. Only 1.5 wt % Pt was added to achieve maximum hydrogen release. Subsequently, triphenylamine was employed as a strong donor and N+ can act as a strong acceptor, and iCON-4 synthesized by the strong–strong union method exhibits a hydrogen production efficiency of 9519 μmol g–1 h–1, which is the highest among iCON-(1–4). Interestingly, the extremely wide visible-light absorption range of iCON-(3–4) extends to about 700 nm and exceeds most photocatalytic semiconductor materials and provides a prerequisite for water decomposition. This work highlights a design concept for PHE in terms of hydrophilicity, dispersivity, charge-carrier separation, and band regulation. It is worth mentioning that iCONs are fabricated by the one-pot method and have not been employed to PHE before.