Journal
ACS CATALYSIS
Volume 13, Issue 9, Pages 5969-5978Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.3c00053
Keywords
conjugated microporous polymer; Re(I)-integration; photocatalysis; CO2 reduction; sacrificial agent; selectivity
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One of the major challenges in photocatalytic CO2 reduction is achieving control over the selective formation of a single product while maintaining a high conversion efficiency. In this study, a conjugated microporous polymer (TEB-BPY) was synthesized and characterized, and it was found that Re@TEB-BPY exhibited high photocatalytic activity for CO2 reduction to CO or CH4. The presence of triethylamine (TEA) or 1-benzyl-1,4-dihydronicotinamide (BNAH) as sacrificial electron donors influenced the selectivity of the products.
One of the major challenges in photocatalytic CO2 reduction is achieving control over the selective formation of a single product while maintaining a high conversion efficiency. Here, we report the synthesis and characterization of a conjugated microporous polymer (TEB-BPY) formed by C-C coupling between 1,3,5-triethynylbenzene and 5,5 '-dibromo-2,2 '-bipyridine. Further, [Re(CO)5Cl] covalently integrated with the polymer, and the resulting metalated Re@TEB-BPY polymer was used as a catalyst for the visible-light-driven CO2 reduction. Re@TEBBPY displays photoconversion of CO2 to CO with a production rate of 91.7 mu mol g-1 h-1 and a selectivity of similar to 68% in the presence of triethylamine (TEA) as the sole sacrificial electron donor. Interestingly, CH4 is produced as a major product instead of CO when CO2 reduction was performed using 1-benzyl-1,4-dihydronicotinamide (BNAH) as a sacrificial electron donor in the presence of TEA as a base. In this reaction, Re@TEB-BPY produces CH4 as the major product with a rate of 2.05 mmol g-1 h-1 (selectivity of similar to 96% and apparent quantum efficiency of 0.22%). From an in situ diffuse reflectance FTIR spectroscopy (DRIFTS) study together with DFT calculations, a possible catalytic cycle for CO2 reduction to CO or CH4 is constructed. Theoretical calculations along with control experiments further reveal that TEA acts mainly as a base in the presence of BNAH to suppress the back electron transfer process, resulting in enhanced photocatalytic activity.
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