π–π Stacking as Electron-Transfer Channels in Hydrogen-Bonded Organic Frameworks for Boosting Photocatalysis

Photocatalysis provides a promising approach to produce green energy, by which the intermittent solar energy can be converted into storable chemical energy. It is well-known that the electron-transfer rate has great influence on the photocatalytic efficiency. Revealing the influence of electron-transfer rate on the photocatalytic efficiency from a molecular level is of great significance but a challenge. Herein, we give solid evidence to show that the π–π stacking can serve as an electron-transfer channel to boost photocatalysis. Specifically, two hydrogen-bonded organic frameworks (HOFs) with similar structures but slightly different intermolecular interactions have been weaved. Interestingly, the HOF with π–π stacking interactions shows much higher photocatalytic activity for hydrogen evolution than the one without. Further structural and spectroscopic analyses revealed that the much-enhanced photocatalytic activity of the former can be attributed to the π–π stacking, which can really serve as an electron-transfer channel, thus accelerating the electron transfer and achieving a remarkably enhanced activity in photocatalytic hydrogen evolution. The work, from a molecular level, reveals the role of π–π stacking in photocatalysis and gives new insights into the electron-transfer in photocatalysts.