Modulating photon harvesting through dynamic non-covalent interactions for enhanced photochemical CO2 reduction

A novel and practicable pseudo-supramolecular assembly at a molecular scale by dynamic conjugation with ultra-small NCQDs as ultraviolet-visible light chromophore to promote the photosensitization efficiency of Ru molecules for photochemical CO 2 reduction to CO in both homogeneous and heterogeneous systems. • The concept of pseudo-supramolecular assembly is proposed involving the NCQDs and Ru complex. • The spatially reversible assembly process is driven by the dynamic non-covalent interactions. • UV–vis light can be effectively utilized to enhance the photon-harvesting efficiency of Ru complex. • The promotion effect is demonstrated in both homogeneous and heterogeneous CO 2 reduction systems. Molecular transition metal complexes are widely explored in artificial photosynthetic redox catalysis due to their extraordinary properties. However, these catalysts generally suffer from the intrinsic thresholds of photon harvesting efficiency and spectrum response range, greatly limiting their further applications. Polypyridyl ruthenium ( Ru ) has been perceived as a paradigmatic photosensitizer in CO 2 reduction systems but seldomly maneuvered. Herein, we develop a novel and practicable pseudo-supramolecular assembly at a molecular scale by conjugation with ultra-small nitrogen-doped carbon quantum dots (NCQDs) as ultraviolet-visible (UV–vis) light chromophore for enhanced photochemical conversion of CO 2 to CO. The reversible self-assembly of NCQDs with Ru is driven by dynamic non-covalent π-conjugated and electrostatic interactions. Femtosecond transient absorption and time-resolved fluorescence decay spectra combined with control experiment results collaboratively demonstrate that vectorial photo-induced exciton cascade occurs by means of their unique photophysical properties in the as-assembled NCQDs/ Ru dyad, enabling the superior photosensitized CO 2 reduction performance in both homogeneous and heterogeneous systems. This work is expected to not only shed new light on the development of promising artificial light-harvesting systems but also promote the implementation of metal complex-based systems for photoredox-catalyzed reactions.