A novel metal-free porous covalent organic polymer for efficient room-temperature photocatalytic CO2 reduction via dry-reforming of methane

At room temperature, the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane (DRM) is quite promising and challenging. Herein, we developed a novel covalent organic porous polymer (TPE-COP) with rapid charge separation of the electron-hole pairs for DRM driven by visible light at room temperature, which can efficiently generate syngas (CO and H-2). Both electron donor (tris(4-aminophenyl)amine, TAPA) and acceptor (4,4',4'',4'''-((1 ' ,4 '' ,4 '''-((1 E,1'E,1''E, ' E,1 '' E, 1'''E)-(ethene-1,1,2,2-tetrayltetrakis ''' E)-(ethene-1,1,2,2-tetrayltetrakis (benzene4,1-diyl))tetrakis (ethene-2,1-diyl))tetrakis (1-(4-formylbenzyl)quinolin-1-ium), TPE-CHO) were existed in TPE-COP, in which the push-pull effect between them promoted the separation of photogenerated electron-hole, thus greatly improving the photocatalytic activity. Density functional theory (DFT) simulation results show that TPE-COP can form charge-separating species under light irradiation, leading to electrons accumulation in TPE-CHO unit and holes in TAPA, and thus efficiently initiating DRM. After 20 h illumination, the photocatalytic results show that the yields reach 1123.6 and 30.8 mu mol g(-1) for CO and H-2, respectively, which are significantly higher than those of TPE-CHO small molecules. This excellent result is mainly due to the increase of specific surface area, the enhancement of light absorption capacity, and the improvement of photoelectron-generating efficiency after the formation of COP. Overall, this work contributes to understanding the advantages of COP materials for photocatalysis and fundamentally pushes metal-free catalysts into the door of DRM field. (c) 2023 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).