Chafin Ryan, Sujan Majharul Islam, Parkin Sean, Jurss Jonah W, Huckaba Aron J
Department of Chemistry, University of Kentucky Lexington KY 40506 USA
Department of Chemistry and Biochemistry, University of Mississippi Mississippi 38677 USA.
RSC Adv. 2025 Apr 22;15(16):12547-12556. doi: 10.1039/d5ra01561h. eCollection 2025 Apr 16.
Removing carbon dioxide from the atmosphere is an attractive way to mitigate the greenhouse gas effect that contributes to climate change. A series of donor-pi (D-π), acceptor-pi (A-π), and π Re(i) pyridyl imidazole complexes have been synthesized and examined under photocatalytic conditions for the photocatalytic reduction of CO. The catalytic activity of the complexes was further supported by cyclic voltammetry through the presence of a catalytic current under CO atmosphere. The D-π, π, and A-π complexes were studied to elucidate the effects of incorporating conjugated electron donating withdrawing groups on the catalytic rates and product selectivity. The synthesized complexes were compared with Re(bpy)(CO)Br (where bpy is 2,2'-bipyridine), the benchmark catalyst for this transformation. Remarkably, the complex with A-π pendant (RC4) outperformed the π (RC2-3) and D-π (RC5) complexes for the production of formic acid (HCOH) in the presence of photosensitizer [Ru(bpy)] and sacrificial electron donor BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1-benzo[]-imidazoline). Among the investigated catalysts, RC4 with the A-π pendant showed the highest turnover number (TON) value of 844 for HCOH production with 86% carbon selectivity. In stark contrast to the imidazole-pyridine based catalysts reported here that favor formic acid as a product, Re(bpy)(CO)Br generated no formic acid under the same conditions. The imidazole-pyridine complexes also function as catalysts for CO reduction without an added photosensitizer, however, the TON values under self-sensitized conditions are poor.
从大气中去除二氧化碳是减轻导致气候变化的温室气体效应的一种有吸引力的方法。一系列给体-π（D-π）、受体-π（A-π）和π Re(i)吡啶基咪唑配合物已被合成，并在光催化条件下用于光催化还原CO的研究。通过在CO气氛下存在催化电流，循环伏安法进一步支持了配合物的催化活性。对D-π、π和A-π配合物进行了研究，以阐明引入共轭给电子/吸电子基团对催化速率和产物选择性的影响。将合成的配合物与该转化的基准催化剂Re(bpy)(CO)Br（其中bpy为2,2'-联吡啶）进行了比较。值得注意的是，在存在光敏剂[Ru(bpy)]和牺牲电子给体BIH（1,3-二甲基-2-苯基-2,3-二氢-1-苯并咪唑）的情况下，具有A-π侧基的配合物（RC4）在甲酸（HCOH）生成方面优于π（RC2-3）和D-π（RC5）配合物。在所研究的催化剂中，具有A-π侧基的RC4在HCOH生成方面表现出最高的周转数（TON）值844，碳选择性为86%。与本文报道的有利于生成甲酸的咪唑-吡啶基催化剂形成鲜明对比的是，Re(bpy)(CO)Br在相同条件下不生成甲酸。咪唑-吡啶配合物在不添加光敏剂的情况下也可作为CO还原的催化剂，然而，自敏化条件下的TON值较低。
