Zhao Chengfeng, Yang Chao, Lv Ximeng, Wang Shengyao, Hu Cejun, Zheng Gengfeng, Han Qing
School of Chemistry and Chemical, Beijing Institute of Technology, Beijing, 100081, China.
Laboratory of Advanced Materials, Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Faculty of Chemistry and Materials Science, Fudan University, Shanghai, 200438, China.
Adv Mater. 2024 Jun;36(25):e2401004. doi: 10.1002/adma.202401004. Epub 2024 Apr 1.
Photocatalytic reduction of CO into syngas is a promising way to tackle the energy and environmental challenges; however, it remains a challenge to achieve reaction decoupling of CO reduction and water splitting. Therefore, efficient production of syngas with a suitable CO/H ratio for Fischer-Tropsch synthesis can hardly be achieved. Herein, bipolaronic motifs including Co(II)-pyridine N motifs and Co(II)-imine N motifs are rationally designed into a crystalline imine-linked 1,10-phenanthroline-5,6-dione-based covalent organic framework (bp-Co-COF) with a triazine core. These featured structures with spatially separated active sites exhibit efficient photocatalytic performance toward CO-to-syngas conversion with a suitable CO/H ratio (1:1-1:3). The bipolaronic motifs enable a highly separated electron-hole state, whereby the Co(II)-pyridine N motifs tend to be the active sites for CO activation and accelerate the hydrogenation to form *COOH intermediates; whilst, the Co(II)-imine N motifs increase surface hydrophilicity for H evolution. The photocatalytic reductions of CO and HO thus decouple and proceed via a concerted way on the bipolaronic motifs of bp-Co-COF. The optimal bp-Co-COF photocatalyst achieves a high syngas evolution rate of 15.8 mmol g h with CO/H ratio of 1:2, outperforming previously reported COF-based photocatalysts.
光催化将CO还原为合成气是应对能源和环境挑战的一种很有前景的方法；然而，实现CO还原和水分解的反应解耦仍然是一个挑战。因此，很难高效生产出具有适合费托合成的CO/H比的合成气。在此，将包括Co(II)-吡啶N基序和Co(II)-亚胺N基序的双极子基序合理设计到一种具有三嗪核的结晶亚胺连接的基于1,10-菲咯啉-5,6-二酮的共价有机框架（bp-Co-COF）中。这些具有空间分离活性位点的特色结构对CO到合成气的转化表现出高效的光催化性能，且具有合适的CO/H比（1:1 - 1:3）。双极子基序实现了高度分离的电子 - 空穴态，其中Co(II)-吡啶N基序倾向于成为CO活化的活性位点并加速氢化以形成*COOH中间体；同时，Co(II)-亚胺N基序增加了析氢的表面亲水性。因此，CO和H₂O的光催化还原解耦，并在bp-Co-COF的双极子基序上以协同方式进行。最佳的bp-Co-COF光催化剂在CO/H比为1:2时实现了15.8 mmol g⁻¹ h⁻¹的高合成气析出速率，优于先前报道的基于COF的光催化剂。
