Unveiling the Activity and Mechanism Alterations by Pyrene Decoration on a Co(II) Macrocyclic Catalyst for CO₂ Reduction

Abstract

Mechanistic studies involving characterization of crucial intermediates are desirable for rational optimization of molecular catalysts toward CO2 reduction, while fundamental challenges are associated with such studies. Herein we present the systematic mechanistic investigations on a pyrene‐appended CoII macrocyclic catalyst in comparison with its pyrene‐free prototype. The comparative results also verify the reasons of the higher catalytic activity of the pyrene‐tethered catalyst in noble‐metal‐free CO2 photoreduction with various photosensitizers, where a remarkable apparent quantum yield of 36±3% at 425 nm can be obtained for selective CO production. Electrochemical and spectroelectrochemical studies in conjunction with DFT calculations between the two catalysts have characterized the key CO‐bound intermediates and revealed their different CO‐binding behavior, demonstrating that the pyrene group endows the corresponding CoII catalyst a lower catalytic potential, a higher stability, and a greater ease in CO release, all of which contribute to its better performance.

Directed Electron Delivery from a Pb‐Free Halide Perovskite to a Co(II) Molecular Catalyst Boosts CO2 Photoreduction Coupled with Water Oxidation

“…Molecular catalysts based on metal complexes are of high efficiency with their well-defined structures and facile mechanistic studies. [19][20][21][22][23] But their performances are limited by moderate stability, poor conductivity and aggregation tendencies, [24] which can also be circumvented by their rational dispersion on suitable functional surfaces. Previous studies have tried to immobilize a Re-bipyridine, [10] a Ni-terpyridine [11] or a Fe-porphyrin [16] catalyst on CsPbBr 3 nanocrystals, or a dinuclear Co-cryptate catalyst on Pb-free Cs 3 Sb 2 Br 9 hollow nanospheres, [9] most of which utilized different organic sacrificial reagents, to achieve good performances in CO 2 photoreduction.…”

Highly Efficient, Noble-Metal-Free, Fully Aqueous CO2 Photoreduction Sensitized by a Robust Organic Dye

“…Homogeneous, molecular photocatalytic systems are appealing in this term for the highly optimizable structures of the main molecular components, i.e., catalyst and photosensitizer (PS), in which their optimizations can be oriented by their well-defined structure–activity relationship and photocatalytic mechanisms. ,− Although selective molecular catalysts for photocatalytic CO 2 reduction in fully aqueous media have been developed, as exemplified by those earth-abundant ones like cobalt porphyrins, ,− Ni cyclam, ,− etc., the design of a versatile PS remains as one of the major bottlenecks to further improve the photocatalytic performance. As shown in Figure , one of the representative PSs in aqueous solutions is Ru­(bpy) 3 2+ (bpy = 2,2′-bipyridine; denoted as RuBPY ; Figure ), ,,,− which still relies on the use of precious metal, restricting the large-scale applications.…”