CoII-organic ‘soft’ metallo-supramolecular polymer nanofibers for efficient photoreduction of CO2†
Abstract
Coordination-driven metallo-supramolecular polymers hold significant potential as highly efficient catalysts for photocatalytic CO2 reduction, owing to the covalent integration of the light harvesting unit, catalytic center and intrinsic hierarchical nanostructures. In this study, we present the synthesis, characterization, and gelation behaviour of a novel low molecular weight gelator (LMWG) integrating a benzo[1,2-b:4,5-b′]dithiophene core with terpyridine (TPY) units via alkyl amide chains (TPY-BDT). The two TPY ends of the TPY-BDT unit efficiently chelate with metal ions, enabling the formation of a metallo-supramolecular polymer that brings together the catalytic center and a photosensitizer in close proximity, maximizing catalytic efficiency for CO2 reduction. The self-assembly of TPY-BDT with CoII ions yields a Co-TPY-BDT coordination polymer gel (CPG) with a 3D interconnected fibrous morphology, facilitating rapid electron transfer and efficient substrate diffusion. The Co-TPY-BDT CPG achieves an outstanding CO2 to CO conversion, producing 33.74 mmol g−1 of CO in 18 hours with ∼99% selectivity under visible light irradiation, using triethylamine (TEA) as a sacrificial electron donor. Remarkably, the Co-TPY-BDT CPG demonstrates significant catalytic activity even under low-concentration CO2 atmospheres (5% CO2, 95% Ar), producing 1.9 mmol g−1 of CO in 10 hours with a selectivity of 94.6%. Moreover, In situ diffuse reflectance Fourier transform (DRIFT) study, femtosecond transient absorption spectroscopy, and DFT calculations were employed to elucidate the CO2 to CO reaction mechanism.