Confining Molecular Photosensitizer and Catalyst in MOF toward Artificial Photosynthesis: Validating Electron Transfer by In Situ DRIFT Study

Exploration of different chemical systems for photocatalyticCO(2) reduction by using sunlight en route to the achievementofartificial photosynthesis stems from global warming and the energycrisis. In this work, we have covalently grafted the molecular photosensitizer(PS) [Ru-(MBA)-(bpy)(2)]-Cl-2 (bpy: 2,2 '-bipyridine)and the catalyst [Mn-(MBA)-(CO)(3)Br] inside the Zr-MOF-808(Zr-MOF) nanopore postmodified with 2-(5 '-methyl-[2,2 '-bipyridine]-5-yl)-aceticacid (H-MBA) and developed a single integrated system named Zr-MBA-Ru/Mn-MOF for the CO2 reduction reaction(CO2RR). Zr-MBA-Ru/Mn-MOF is found to be activetoward CO2-to-CO conversion, with a maximum productionof 1027 mu mol g(-1) after 26 h of reaction having>99% selectivity in the aqueous medium without any additional holescavenger. The catalyst with direct sunlight in the aqueous mediumis equally active for CO production, thus mimicking the natural photosyntheticprocess. We have performed an in situ diffuse reflectanceFourier transform infrared spectroscopy (FTIR) (DRIFT) study to unveilthe electron transfer from the PS to the catalytic center during CO2 reduction by monitoring the changes in the carbonyl stretchingfrequency in the [Mn-(MBA)-(CO)(3)Br] center and correlatedwith the density functional theory (DFT) calculations. Additionally,we have performed in situ DRIFT spectroscopy to understandthe reaction mechanism for the CO2-to-CO conversion.

Automated summary

Exploration of different chemical systems for photocatalytic CO2 reduction by using sunlight en route to the achievement of artificial photosynthesis. A single integrated system named Zr-MBA-Ru/Mn-MOF for the CO2 reduction reaction (CO2RR) was developed. The catalyst exhibited high activity for CO2-to-CO conversion in the aqueous medium without any additional holescavenger.