Tandem composite of M (Zn, Ga, In)-UIO-66/(HZSM-5)-palygorskite for hydrogenation of carbon dioxide to aromatics

Palygorskite-based HZSM-5 zeolite was prepared through the hydrothermal method using acidified palygorskite as the Si source and supporter. A series tandem composite of M (Zn, Ga, In)-UIO-66/(HZSM-5)-palygorskite was obtained using metal–organic frameworks (UIO-66) as the carrier using the physical mixing method. XRD, SEM, TEM, N2 adsorption–desorption, NH3-TPD, Py-IR, H2-TPR, XPS, and CO2-TPD were used to investigate the composite’s physical and chemical properties. The calcination temperature effect of palygorskite-based HZSM-5 zeolite, Zn to Zr mole ratio, the space distance between Zn-UIO-66 and palygorskite-based HZSM-5 zeolite, and reaction conditions on the catalytic performance of CO2 hydrogenation to aromatics were investigated. Zn-UIO-66/(HZSM-5)-palygorskite showed excellent catalytic performance. CO2 conversion was 21.2% and selectivity for benzene, toluene, and xylene (BTX) were 84.9% under optimal reaction conditions. In situ DRIFTS and Density Functional Theory (DFT) were used to investigate and simulate the CO2 adsorption performance over the Zn-UIO-66 system. In addition, the reaction mechanism of CO2 hydrogenation was explored. The transition state and energy barrier for CO2 hydrogenation to aromatics were obtained by minimum energy search of the LST/QST transition state.