Engineering NGQD@4CzIPN nanorods for efficient photoredox BNAH regeneration and Biginelli cyclocondensation under visible light.

Abstract

The design of highly efficient metal-free photocatalysts for cofactor regeneration is of significant importance for advancing sustainable photo- and biocatalytic systems. In this study, a graphene-based 4CzIPN nanorod photocatalyst (NGQD@4CzIPN) was successfully constructed through non-covalent integration of nitrogen-doped graphene quantum dots (NGQDs) with the organic moiety 2,4,5,6-tetrakis(carbazol-9-yl) isophthalonitrile (4CzIPN). Owing to the synergistic interaction between the two components, characterized by improved interfacial charge transfer and charge-carrier dynamics as evidenced by time-resolved photoluminescence, the resulting NGQD@4CzIPN nanorods exhibit enhanced visible-light absorption and more efficient charge separation compared with pristine 4CzIPN. The photocatalytic performance of the NGQD@4CzIPN nanorods was evaluated for the visible-light-driven reduction of BNA+ to BNAH (1-benzyl-1,4-dihydronicotinamide), achieving a regeneration yield of 58.97%. In addition, the NGQD@4CzIPN nanorod photocatalyst was successfully utilized for Biginelli reactions under visible-light in green solvent media with excellent yields of 3,4-dihydropyrimidin-2-(1H)-one derivatives of up to 91%. To further assess the catalytic efficiency of the system, turnover number (TON) and turnover frequency (TOF) analyses were performed. The superior photocatalytic activity of NGQD@4CzIPN is attributed to efficient interfacial electron transfer, enhanced charge-carrier migration, and suppressed electron-hole recombination within the nanorod architecture. These findings highlight the potential of graphene-derived metal-free nanorod photocatalysts as sustainable and versatile platforms due to less defects in the designed nanorod photocatalyst for cofactor regeneration and valuable multicomponent organic transformations under visible-light irradiation.

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