Covalent-organic frameworks (COFs) have been recognized as a new type of promising photocatalysts for hydrogen evolution. To investigate how different functional groups attached in the backbone of COFs affect the overall photocatalytic H 2 evolution, for the first time, we selected and synthesized a series of ketoenamine-based COFs with the same host framework as model system. It includes TpPaÀ COFÀ X (X =À H, À (CH 3 ) 2 , and À NO 2 ) with three different groups attached in the backbone of TpPaÀ COF. We systematically investigated the differences in morphology, light-absorption intensity and band gap of these 2D COFs. The results of photocatalytic H 2 evolution measurements indicate that the TpPaÀ COFÀ (CH 3 ) 2 shows the best activity, while the activity of TpPaÀ COFÀ NO 2 is relatively low compared to that of other two COFs in the system. Moreover, the separation ability of photogenerated charge was also followed the order of TpPaÀ COFÀ (CH 3 ) 2 > TpPaÀ COF > TpPaÀ COFÀ NO 2 . The best photocatalytic H 2 production performance of TpPaÀ COFÀ (CH 3 ) 2 in these systems should be mainly attributed to the better electron-donating ability of À CH 3 groups compared to À H or À NO 2 group, which result in more efficient charge transferring in the inner of the material. This work demonstrates that reasonably adding electrondonating group in TpPaÀ COFs can lead to a better photocatalytic H 2 evolution activity, and which is meaningful for further design of efficient COF-based photocatalysts for H 2 evolution.[a] J.
A covalently connected rGO–TpPa-1-COF hybrid material synthesized by one-pot reaction for enhanced photocatalytic hydrogen evolution under visible light irradiation.
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