In this paper, we synthesized and evaluated heterogeneous catalysts with varying concentrations of oxygen vacancies on the surface for the hydrogenation of MEA-captured-CO₂ to methanol. The optimized supramolecular catalyst Pt/C_SAP-TiO₂/CeO₂ exhibited the best activity, with 193% higher TONs than the parent Pt/TiO₂ catalyst (45.3 versus 23.4). A novel supramolecular heterogeneous hydrogenation mechanism was also proposed.

Abstract

Integrated CO₂ capture and hydrogenation to methanol is highly likely an economically advantageous technology for flue gas decarbonization and decentralized energy storage. However, highly efficient hydrogenation catalysts are yet to be explored. Herein, we report an efficient metal oxides-carbon-composite supported metal catalyst, Pt/C_SAP-TiO₂/CeO₂, with abundant oxygen vacancies for the highly enhanced hydrogenation of MEA-captured-CO₂ to methanol. An increase in the concentration of oxygen vacancies through catalysts Pt/TiO₂, Pt/TiO₂-CeO₂, and Pt/C_SAP-TiO₂/CeO₂ contributes to an improvement in methanol turnovers and yields, as evidenced by x-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), attenuated total reflectance–Fourier-transform infrared spectroscopy (ATR–FTIR), CO₂-temperature programmed desorption (CO₂-TPD), O 1s X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and catalysis experiments. The optimized supramolecular catalyst Pt/C_SAP-TiO₂/CeO₂ exhibited the best activity, with 193% higher TONs than the parent Pt/TiO₂ catalyst (45.3 versus 23.4). A novel supramolecular heterogeneous catalysis mechanism utilizing the surface oxygen vacancies for absorption, preorganization, activation, and conversion of the key challenging formamide intermediate to methanol is proposed.