Highly active MIL-68(In)-derived In2O3 hollow tubes catalysts to boost CO2 hydrogenation to methanol

Abstract

MIL-68(In)-derived In2O3 hollow tubes with different morphology and size using MIL-68(In) as a template were prepared at different NaOAc concentrations and applied to CO2 hydrogenation to methanol. The size of a series of MIL-68(In) gradually decreased with increasing NaOAc concentration. Too large or small diameter of MIL-68(In) (NaOAc at 0.2 M or 1 M) led to the collapse of corresponding derivative In2O3 tubular structure and only haphazardly accumulated In2O3 nanoparticles were retained. However, the In2O3 hollow tubular-like structure could be obtained when NaOAc concentrations were in the range of 0.4 M to 0.65 M. Interestingly, the self-assembly MIL-68(In)-0.5 M-derived In2O3 with the most regular and perfect hollow tube structure was composed of ordered arrangement of In2O3 nanoparticles at 0.5 M NaOAc, which exhibited much higher methanol synthesis performance than that of other In2O3 catalysts. The lowest surface reduction temperature led to oxygen vacancies easily exposed on In2O3-0.5 M hollow tube surface. The space confinement effect further enhanced the reaction efficiency of oxygen vacancies, and adsorption capacity of CO2 was enhanced to improve the methanol yield. It achieved a CO2 conversion of 14.0%, while methanol selectivity remained at 65%. The space-time yield was up to 1.07 gMeOHh-1gcat-1, showing excellent methanol activity.