Integrated VOCs abatement and CO₂ valorization: Capture and solar fuels production over sustainable materials

The management of the CO2 produced during the catalytic oxidation of volatile organic compounds (VOCs) is a key challenge for the development of sustainable air purification processes. In this work, an integrated approach was investigated, where the CO2 evolved by the catalytic oxidation of toluene, used as a model VOC, was either captured by sustainable zeolite-based cryogels or straightforwardly converted into solar fuels through a photothermo-catalytic route. For the CO2 capture, chitosan/poly(ethylene glycol) diglycidyl ether cryogels containing zeolite 13X were prepared. The presence of zeolite strongly improved the adsorption performance, allowing a capture efficiency of about 70% in the integrated test, whereas a negligible CO2 uptake was obtained with the cryogel without zeolite. For the CO2 conversion, 1 wt% Cu2O-TiO2 supported on Ni/Ce-modified phyllosilicates was examined. Among the investigated samples, the modified kaolinite support showed the best performance, reaching 77% of CO2 conversion after 4 h of solar photothermo-catalytic test at 120 degrees C. The improved activity of this sample was mainly related to the higher amount of basic sites, especially those with medium strength, favouring the adsorption and activation of CO2, whereas the Cu2O-TiO2 mixed oxide promoted the photocatalytic contribution under simulated solar irradiation. The integrated strategy here proposed is promising to couple VOC removal with CO2 capture/utilization using sustainable materials, thus contributing to a circular approach for environmental protection.