Metal organic framework derived In2O3/ZrO2 heterojunctions with interfacial oxygen vacancies for highly selective CO2-to-methanol hydrogenation.

Abstract

The hydrogenation of CO2 to methanol is a promising route for carbon capture and utilization, however achieving high selectivity and productivity remains a challenge. This study presents a novel catalyst synthesized by pyrolyzing a zirconium-based metal-organic framework impregnated with indium, yielding ultrafine In2O3 nanoparticles uniformly embedded within a ZrO2 and carbon matrix. The resulting In2O3/ZrO2 heterojunction exhibited abundant oxygen vacancies at the interface, which is crucial for enhancing the catalytic performance. Under gas-phase conditions, the catalyst achieves an exceptional methanol selectivity of 81% with a record-high productivity of 2.64 gMeOH·gcat⁻¹·h⁻¹ at mild reaction conditions, while in liquid-phase hydrogenation, methanol selectivity reaches 96%. Comprehensive structural characterizations confirmed that oxygen vacancies and the heterointerface served as active sites, facilitating CO2 activation and methanol stabilization. Mechanistic insights from in-situ DRIFTS and ATR-IR spectroscopy revealed that methanol formation proceeds via the formate pathway, further supported by in-situ ambient-pressure X-ray photoelectron spectroscopy, demonstrating electronic structural modulation and an increased concentration of oxygen vacancies. These findings underscore the critical role of defect engineering in optimizing CO2 hydrogenation catalysts and provide a pathway for designing highly efficient systems for sustainable methanol production.