Design and synthesis of a covalent organic framework bridging CdS nanoparticles and a homogeneous cobalt–bipyridine cocatalyst for a highly efficient photocatalytic CO2 reduction,Journal of Materials Chemistry A

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Design and synthesis of a covalent organic framework bridging CdS nanoparticles and a homogeneous cobalt–bipyridine cocatalyst for a highly efficient photocatalytic CO2 reduction
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2023-03-20 , DOI: 10.1039/d3ta00079f
Khai H. Do ₁ , D. Praveen Kumar ₁ , A. Putta Rangappa ₁ , Jehee Lee ₁ , Sungin Yun ₁ , Tae Kyu Kim ₁

Affiliation

The design and construction of highly efficient photocatalytic CO₂ conversion systems are extremely desirable for technological, practical, and economic viability. In this study, a 2,2′-bipyridine (bpy)-based ketoenamine covalent organic framework (TpBpy; Tp: 1,3,5-triformylphloroglucinol), which can be prepared on a large scale by a facile and environmentally friendly hydrothermal method, was used to promote CO₂ photoreduction processes by bridging heterogeneous CdS nanoparticles and a homogeneous [Co(bpy)₃]²⁺ cocatalyst. The bpy units played multiple roles in the preparation of TpBpy, formation of strong interactions with CdS, and accommodation of the cocatalyst. In the CO₂ reduction process, due to the flexible association/dissociation between the bpy ligand and the cocatalyst, the active [Co(bpy)_x]⁺ may separate from heterogeneous CdS/TpBpy and make spaces for other unactive [Co(bpy)₃]²⁺ species, thereby maintaining the intrinsic high activity and selectivity of the [Co(bpy)₃]²⁺ cocatalyst. The combination of CdS, TpBpy, and [Co(bpy)₃]²⁺ shows a strong solar light harvesting ability, a high surface area, a high CO₂ adsorption capacity, highly efficient charge carrier transfer at the interface between CdS and TpBpy, and subsequent rapid photoelectron injection into the [Co(bpy)₃]²⁺ cocatalyst. These synergistic effects lead to a robust CO production rate of 35.2 mmol g⁻¹ with 85.0% selectivity over the first four hours of the reaction. Moreover, the quantum efficiencies (AQEs) of the reaction system, with 2 mg of CdS/TpBpy-20%, are 4.75 and 3.65% at 400 and 450 nm, respectively. Finally, the possible mechanism of the photocatalytic CO₂ conversion over CdS/TpBpy is proposed and discussed here. This study on the heterostructure and photocatalytic system design might serve as a model for the development of solar-driven CO₂ reduction.

中文翻译：

桥接 CdS 纳米粒子和均相钴-联吡啶助催化剂的共价有机框架的设计和合成，用于高效光催化 CO2 还原

高效光催化 CO ₂转化系统的设计和构建对于技术、实用和经济可行性而言是极其理想的。在这项研究中，一种基于 2,2'-联吡啶 (bpy) 的酮烯胺共价有机框架 (TpBpy; Tp: 1,3,5-triformylphloroglucinol)，可以通过简便且环保的水热法大规模制备, 用于通过桥接异质 CdS 纳米粒子和均相 [Co(bpy) ₃ ] ^{2+助催化剂来促进 CO}₂光还原过程。bpy 单元在 TpBpy 的制备、与 CdS 的强相互作用形成以及助催化剂的调节等过程中发挥了多重作用。在二氧化碳₂还原过程中，由于 bpy 配体和助催化剂之间的灵活结合/解离，活性 [Co(bpy) _x ] ⁺可能与异质 CdS/TpBpy 分离并为其他非活性 [Co(bpy) ₃ ] ^{2+腾出空间物种，从而保持 [Co(bpy)}₃ ] ²⁺助催化剂固有的高活性和选择性。_{CdS、TpBpy 和 [Co(bpy) 3} ] ²⁺的组合显示出强大的太阳光收集能力、高表面积、高 CO ₂吸附能力、CdS 和 TpBpy 之间界面的高效载流子转移，以及随后将光电子快速注入 [Co(bpy) ₃ ] ²⁺助催化剂。这些协同效应导致在反应的前四个小时内以 85.0% 的选择性产生35.2 mmol g ^-1的强劲 CO 生产率。此外，具有 2 mg CdS/TpBpy-20% 的反应系统的量子效率 (AQE) 在 400 和 450 nm 处分别为 4.75 和 3.65%。最后，本文提出并讨论了 CdS/TpBpy光催化 CO ₂转化的可能机制。这项关于异质结构和光催化系统设计的研究可以作为开发太阳能驱动 CO _2的模型减少。

更新日期：2023-03-20

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