CuO-Clinoptilolite Composites for Sustainable CO2 Conversion: Modulating Pathways Toward Alcohols

The increasing atmospheric concentration of CO2 is a major contributor to global climate change, underscoring the urgent need for effective strategies to convert CO2 into value-added products. In this sense, a composite was successfully synthesized by combining clinoptilolite zeolite (CZ) with varying amounts of copper oxide (CuO-1% and 10%) for CO2 photoreduction. The composites were characterized using insightful techniques, including XRD, nitrogen physisorption, DRS, and SEM. The results confirmed the incorporation and dispersion of CuO within the CZ support. The XRD analysis revealed characteristic crystalline CuO peaks. Despite the low surface area (<15 m2·g−1) and macroporous nature of the samples, EDS imaging revealed an effective and homogeneous dispersion of CuO, indicating efficient surface distribution. UV–Vis diffuse reflectance spectroscopy revealed band gap energies of 3.30 eV (CZ), 3.38 eV (1%-CuO/CZ), and 1.75 eV (10%-CuO/CZ), highlighting the pronounced electronic changes resulting from CuO incorporation. Photocatalytic tests conducted under UVC irradiation (λ = 254 nm) revealed that 10%-CuO/CZ exhibited the highest CO and CH4 production, 35 µmol·g−1 and 3.6 µmol·g−1, respectively. The composite also delivered the highest CO productivity (5.91 µmol·g−1·h−1), approximately 3.5 times that of pristine CZ, in addition to achieving the highest CH4 productivity (0.60 µmol·g−1·h−1). Furthermore, turnover frequency (TOF) analysis normalized per Cu site revealed that CuO incorporation not only enhances total productivity but also improves the intrinsic catalytic efficiency of the active copper centers. Overall, the synthesized composites demonstrate promising potential for CO2 photoreduction, driven by synergistic structural, electronic, and morphological features.