Effect of Different Functional Groups on Photocatalytic Hydrogen Evolution in Covalent‐Organic Frameworks

Abstract

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.

Covalent organic framework photocatalysts: structures and applications

“…Later, three Ketoenamine-based COFs were investigated to explore the effect of different groups on photocatalytic performance. 180 Specifically, TpPa-COF-X (X = -H, -(CH3)2, and -NO2) were constructed from the same host backbone with different functional groups anchored on the framework. In the photocatalytic experiment, H2 evolution efficiency decreased in the order of TpPa-COF-(CH3)2 > TpPa-COF > TpPa-COF-NO2.…”

Covalent Organic Frameworks for Efficient Energy Electrocatalysis: Rational Design and Progress

“…For example, Sun, Zhang, and coworkers synthesized a series of ketoenamine‐based COFs using the same host framework (TpPa‐COF) as the model system ( Figure a). [ 96 ] Three types of functional groups (–H, –(CH 3 ) 2 , and –NO 2 ) were attached in the backbone of TpPa‐COF by selecting diverse building units, where TpPa‐COF‐(CH 3 ) 2 shows the strongest photoabsorption (Figure 14b). Mott–Schottky results demonstrated a remarkable characteristic of n‐type semiconductors for all as‐synthesized samples (Figure 14c).…”

“…Reproduced with permission. [ 96 ] Copyright 2019, Wiley‐VCH. f) Digital photos of imine‐linked COF and Ru@COF.…”

Two‐Dimensional Covalent‐Organic Frameworks for Photocatalysis: The Critical Roles of Building Block and Linkage

“…The photocatalytic activity (Pt as co‐catalyst) of TpPa‐COF‐(CH 3 ) 2 (8330 μmol g −1 h −1 ) was much higher than those of TpPa‐COF‐(NO 2 ) 2 (220 μmol g −1 h −1 ) and TpPa‐1‐COF (156 μmol g −1 h −1 ) which were in line with electron‐donating ability of these three functional groups. [ 91 ] The composite, MoS 2 /TpPa‐1‐COF (3%wt MoS 2 ), displayed a high hydrogen production rate of 5585 μmol g −1 h −1 in the absence of Pt. [ 92 ] In addition, a series of Z‐scheme heterojunction based on 2D COFs were also reported and displayed outstanding HER performance.…”