Unraveling the\nKey Factors on Structure–Property–Activity\nCorrelations for Photocatalytic Hydrogen Production of Covalent Organic\nFrameworks

It\nhas been a challenging task to clearly elucidate various\nstructural\nfeatures and how their interactions affect the photocatalytic hydrogen\nproduction performance. In this work, various factors, including crystallinity,\nspecific surface area associated with morphology, energy band gap\nand energy levels, surface charge, and hydrophilicity, were employed\nto investigate the structure–property–activity correlations\nof β-ketoenamine-linked covalent organic framework (TpPa-1-COF)\nfor photocatalytic H<sub>2</sub> production, which could influence\nthe light harvesting, charge separation and transfer, and surface\ncatalytic active sites. By using different methods to prepare TpPa-1-COFs,\nwe can regulate these influencing factors to investigate their relationship\nwith activity. It is found that the TpPa-1-COF prepared by a molecular\norganization method (labeled as TpPa-1 (MO)) exhibits the highest\nphotocatalytic H<sub>2</sub> evolution activity compared with the\nTpPa-1-COF samples prepared by solvothermal methods using acetic acid\n(HOAc) as a catalyst (TpPa-1 (ST-HOAc)) and KOH solution as a catalyst\n(TpPa-1 (ST-KOH)), which is associated with the highest crystallinity,\nthe optimal energy levels, the largest BET-specific surface area,\nand the best hydrophilicity for TpPa-1 (MO). Moreover, our findings\nsuggest that the enhanced total photocatalytic H<sub>2</sub> evolution\nefficiency (η<sub>total</sub>) of TpPa-1 (MO) may be mainly\nattributed to the efficient separation and migration of photogenerated\ncharges (η<sub>2</sub>) and the vibrant surface catalytic active\nsites (η<sub>3</sub>). Overall, this work provides some deep\ninsights into the structure–property–activity relation\nof TpPa-1-COF photocatalysts, which offers valuable inspiration and\nguidance for the thoughtful design of COF-based photocatalysts for\nH<sub>2</sub> evolution.