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.