Metal-organic framework-derived Fe3O4-FeCx catalyst for direct CO2 hydrogenation to light olefins

Converting carbon dioxide into lower olefins (C2=-C4=) through hydrogenation is a crucial chemical reaction that allows for the use of CO2 as carbon source in the production of foundational chemicals. Herein, nitrogen-doped carbon-coated iron-based catalysts were obtained by pyrolysis NH2-MIL-88B under N2 atmosphere. The results show that the catalyst morphology, particle size and Fe phase structure can be controlled by changing the pyrolysis conditions. As the temperature rises, the structure starts to deteriorate, resulting in a gradual increase in the iron content and particle size. Fe3O4 and Fe3C phases appeared in the 350/500 °C two-stage pyrolysis, and the two-stage pyrolysis could effectively alleviate the structural collapse of MOFs precursors during the pyrolysis process. With the catalyst obtained by 350/500 °C two-stage pyrolysis, the conversion of CO2 could reach 35.1% and the selectivity of light olefins reached 37.7% (340 °C, 3 MPa, and GHSV= 5000 mL gcat-1 h-1).