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

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 CO2 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 CO2 to CO. The reversible self-assembly of NCQDs with Ru is driven by dynamic non-covalent pi-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 CO2 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.

Automated summary

A novel pseudo-supramolecular assembly is developed by conjugating ultra-small nitrogen-doped carbon quantum dots with polypyridyl ruthenium, enhancing the photochemical conversion of CO2 to CO. The reversible self-assembly driven by dynamic non-covalent interactions led to superior photosensitized CO2 reduction performance, demonstrating potential for promising artificial light-harvesting systems using metal complex-based systems for photoredox-catalyzed reactions.