Bimetallic metal organic framework-templated synthesis of a Cu-ZnO/Al2O3 catalyst with superior methanol selectivity for CO2 hydrogenation

Abstract

It is highly desirable to develop inexpensive and highly selective catalyst for CO2 hydrogenation to methanol and Cu/ZnO/Al2O3 is a promising formulation. Herein, we report the design and synthesis of a Cu-ZnO/Al2O3 catalyst via a bimetallic metal organic framework (MOF)-templated strategy (termed Cu-ZnOMOF⊂Al2O3) and shed light on the role of the Cu-Zn@MOF precursor in this system for methanol synthesis. The developed Cu-ZnOMOF⊂Al2O3 exhibited high methanol selectivity (86.9%) and methanol space-time yield (407.2 gMeOH•kgcat−1•h−1) at higher CO2 conversion (9.1%) in comparison with the conventional Cu-ZnONO3/Al2O3 catalyst (79.6% and 209.0 gMeOH•kgcat−1•h−1, and 5.1%, respectively) at 240 ºC under 3.0 MPa. Spectroscopic characterization (TEM, XPS, EDX, in-situ DRIFTS) coupled with N2O chemisorption and temperature-programmed desorption of CO2 and H2 revealed that the surface of the new Cu-ZnOMOF⊂Al2O3 catalyst possesses higher Cu dispersion, surface-enriched ZnO and more Cu-ZnO interfacial sites, which leads to higher capability for CO2 and H2 adsorption and activation. These are considered to be the origin of higher methanol selectivity and enhanced activity of the catalyst prepared by the MOF-templated strategy for CO2 hydrogenation. This work offers a novel approach to optimizing Cu-ZnO/Al2O3 catalyst for CO2 hydrogenation to methanol.