Z-scheme heterojunction of chemically integrated COF-366-Co/UiO-66-NH2 MOFs nanocomposites for selective production of CO via CO2 solar-drive photoreduction

The photocatalytic conversion of CO2 to renewable fuel using solar energy has recently become an interesting topic, owing to its potential to replace fossil fuels. However, the low efficiency and selectivity of photocatalysis hinder the development of this method for practical applications. In this work, a composite photocatalyst composed of UiO-66-NH2 and COF-366-Co materials is developed using a facile synthetic route with varying concentrations of UiO-66-NH2. The optimized COF-366-Co/UiO-66-NH2 composite exhibited a remarkable efficiency of CO2 photoreduction toward the CO production, reaching - 4092.16 & mu;mol. g-1.h-1 at the end of 4 h, which is around 2.37 times higher than the bare COF, while maintaining a significant CO selectivity at ca 73.28 %. The apparent quantum yield (AQY) of the composite photocatalyst is estimated to be -2.4 %. at 400 nm, which is one of the promising values in the CO2 photoreduction reaction. Parametric studies by varying various components revealed the key mechanism of the photoreduction process. The electrochemical impedance, timeresolved, steady state photoluminescence, linear sweep voltammetry and photocurrent measurements of the systems revealed that the incorporation of UiO-66-NH2 to COF-366-Co has enhanced the properties of the system by improving the lifetime of the excited carriers via electron delocalization and transfer of carriers to the adsorbed CO2 for their effective reduction to CO. Furthermore, the estimated band edge potential of the systems using Mott-Schottky plots suggested that there could be a Z-scheme formation, which mediates the charge transfer at the junction towards achieving an enhanced CO2 photoreduction efficiency and selectivity. This research could promote the development of porphyrin-based COF/MOF-based composites for selective CO2 photoconversion into value-added chemicals and fuels.