Visible-light-driven CO 2 reduction to valuable chemicals without sacrificial agents and co-catalysts remains challenging, especially for metal-free photocatalytic systems. Herein, we report a novel donor-acceptor (D-A) COF (CT-COF) that was constructed by the Schiff base reaction of carbazole-triazine based D-A monomers and possessed a suitable energy band structure, strong visible-light-harvesting and rich nitrogen sites. CT-COF used as a metal-free photocatalyst can reduce CO 2 with gaseous H 2 O to CO as the main carbonaceous product with the approximate stoichiometric O 2 evolution under visible light irradiation and co-catalysts free conditions. The CO evolution rate (102.7 μmol g -1 h -1 ) is 68.5 times that of g-C 3 N 4 under the same test conditions. In situ FT-IR analysis indicates that CT-COF could adsorb and activate the CO 2 and H 2 O molecules and that COOH* species may be a key intermediate. DFT calculations suggest that nitrogen atoms in the triazine rings may be photocatalytic active sites.

中文翻译：

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一种无金属的施主-受体共价有机骨架光催化剂，用于可见光驱动的H2O还原CO2。

在不使用牺牲剂和助催化剂的情况下，将可见光驱动的CO 2还原为有价值的化学品仍然具有挑战性，尤其是对于无金属的光催化系统而言。在这里，我们报告了一种新型的供体-受体（DA）COF（CT-COF），它是通过咔唑-三嗪基DA单体的席夫碱反应构建的，具有合适的能带结构，强大的可见光捕获能力和丰富的氮网站。用作无金属光催化剂的CT-COF可在可见光照射和无助催化剂条件下，将气态H 2 O的CO 2还原为以CO为主要碳质产物，化学计量比为O 2。在相同的测试条件下，CO的释放速率（102.7μmolg -1 h -1）是gC 3 N 4的68.5倍。FT-IR原位分析表明CT-COF可以吸附和活化CO 2和H 2 O分子，COOH *可能是关键的中间体。DFT计算表明三嗪环中的氮原子可能是光催化活性位点。