Wang Wei, Deng Chaoyuan, Xie Shijie, Li Yangfan, Zhang Wanyi, Sheng Hua, Chen Chuncheng, Zhao Jincai
Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, PR China.
University of Chinese Academy of Sciences, Beijing, 100190, PR China.
J Am Chem Soc. 2021 Feb 24;143(7):2984-2993. doi: 10.1021/jacs.1c00206. Epub 2021 Feb 11.
To realize the evolution of C hydrocarbons like CH from CO reduction in photocatalytic systems remains a great challenge, owing to the gap between the relatively lower efficiency of multielectron transfer in photocatalysis and the sluggish kinetics of C-C coupling. Herein, with Cu-doped zeolitic imidazolate framework-8 (ZIF-8) as a precursor, a hybrid photocatalyst (CuO@p-ZnO) with CuO uniformly dispersed among polycrystalline ZnO was synthesized. Upon illumination, the catalyst exhibited the ability to reduce CO to CH with a 32.9% selectivity, and the evolution rate was 2.7 μmol·g·h with water as a hole scavenger and as high as 22.3 μmol·g·h in the presence of triethylamine as a sacrificial agent, all of which have rarely been achieved in photocatalytic systems. The X-ray absorption fine structure spectra coupled with in situ FT-IR studies reveal that, in the original catalyst, Cu mainly existed in the form of CuO, while a unique Cu surface layer upon the CuO matrix was formed during the photocatalytic reaction, and this surface Cu site is the active site to anchor the in situ generated CO and further perform C-C coupling to form CH. The C-C coupling intermediate *OC-COH was experimentally identified by in situ FT-IR studies for the first time during photocatalytic CO reduction. Moreover, theoretical calculations further showed the critical role of such Cu sites in strengthening the binding of *CO and stabilizing the C-C coupling intermediate. This work uncovers a new paradigm to achieve the reduction of CO to C hydrocarbons in a photocatalytic system.
在光催化体系中，要实现通过CO还原生成像CH这样的含碳氢化合物的演化仍然是一个巨大的挑战，这是由于光催化中多电子转移效率相对较低与C-C偶联动力学缓慢之间存在差距。在此，以铜掺杂的沸石咪唑酯骨架-8（ZIF-8）为前驱体，合成了一种CuO均匀分散在多晶ZnO中的复合光催化剂（CuO@p-ZnO）。光照下，该催化剂表现出将CO还原为CH的能力，选择性为32.9%，以水作为空穴清除剂时演化速率为2.7 μmol·g⁻¹·h⁻¹，在三乙胺作为牺牲剂存在的情况下高达22.3 μmol·g⁻¹·h⁻¹，这些在光催化体系中很少能实现。X射线吸收精细结构光谱结合原位傅里叶变换红外光谱研究表明，在原始催化剂中，Cu主要以CuO的形式存在，而在光催化反应过程中在CuO基体上形成了独特的Cu表面层，这个表面Cu位点是锚定原位生成的CO并进一步进行C-C偶联以形成CH的活性位点。通过原位傅里叶变换红外光谱研究首次在光催化CO还原过程中实验鉴定出C-C偶联中间体OC-COH。此外，理论计算进一步表明了这种Cu位点在加强CO的吸附和稳定C-C偶联中间体方面的关键作用。这项工作揭示了在光催化体系中实现将CO还原为含碳氢化合物的新范例。
