UV-Light-Driven Photocatalytic CO2 Reduction over a Niobium-Based Metal–Organic Gel

The photocatalytic conversion of carbon dioxide (CO2) into methanol represents a promising strategy for both greenhouse gas mitigation and renewable fuel production. In this study, a niobium-based metal–organic gel (Nb-MOG) was employed as a photocatalyst for the reduction of CO2 to methanol under UV irradiation in a batch photoreactor. A two-factor experimental design was conducted to evaluate the effects of sodium carbonate concentration and catalyst loading on methanol production. The Nb-MOG catalyst was dispersed in the reaction medium and irradiated with UV light for four hours. During the photocatalytic experiments, samples were periodically collected and analyzed by headspace gas chromatography coupled with flame ionization detection (HS-GC-FID) to quantify methanol production. The results showed that both the Na2CO3 concentration and catalyst loading exerted significant positive effects on methanol formation. The highest methanol yield was achieved at a Na2CO3 concentration of 0.10 mol·L−1 and a catalyst loading of 0.50 g·L−1. The experimental design results demonstrated a good fit of the statistical model to the experimental data, highlighting its predictive capability and confirming the reliability of the obtained results. Furthermore, Nb-MOG exhibited enhanced light-harvesting and charge-transfer properties, leading to measurable methanol production under the investigated conditions. These findings contribute to a better understanding of Nb-MOG’s photocatalytic behavior and demonstrate its potential for application in a sustainable CO2 reduction system.