Arylboron functional covalent organic frameworks for synergistic photocatalytic hydrogen evolution†
Abstract
Covalent organic frameworks (COFs) are attractive organic polymers that can serve as promising photocatalysts for water reduction. Herein, two novel arylboron functional COFs, TAB-TFB-COF and TAB-TFP-COF, were synthesized and their photocatalytic hydrogen evolution ability was evaluated. Under visible light irradiation (λ > 420 nm), the hydrogen evolution rate of TAB-TFP-COF is 666.4 μmol g−1 h−1 at the stationary point (0.5 g L−1), reaching 1140 μmol g−1 h−1 after long cycle stabilization, which is 76 and 1.4 times higher than that of TAB-TFB-COF (8.8 μmol g−1 h−1) and TAB-TFP-CMP (489.6 μmol g−1 h−1), respectively. It is demonstrated that the construction of β-ketoenamine improves the separation and transfer ability of light-induced charge carriers. Specifically, F−-loading experiments and density functional theory (DFT) calculations suggested that the introduction of arylboron units promoted intramolecular charge transfer which was conducive to photocatalytic reactions. Overall, the good photocatalytic performance of TAB-TFP-COF is due to the synergistic catalytic effect of arylboron and β-ketoenamine dual acceptors. The arylboron functionalization may open up new avenues for the development of COFs in photocatalytic materials, making them promising for a variety of applications as advanced solar energy conversion platforms.