The effect of zirconia as a promoter on Cu/MOF-5 catalysts for CO2 hydrogenation to methanol

The rise in carbon dioxide concentration is a primary anthropogenic source of severe climate change and ecological issues. Catalytic hydrogenation of CO2 into value-added chemicals and fuels including methanol is one of the attractive environmentally friendly ways to valorize carbon-containing feedstock and reduce global CO2 emissions. However, enhancing catalytic activity to achieve high methanol yield and selectivity while maintaining stability remains a major challenge. This study investigated the promotion of Cu/MOF-5 catalysts with varying loadings of ZrO2 to determine its effects on catalytic performance in CO2 hydrogenation. The copper loading was kept constant while the ZrO2 content on the MOF-5 support was varied via the impregnation method. The addition of ZrO2was found to influence the BET surface area, suggesting the presence of amorphous ZrO2, as its crystalline phases were not detected in x-ray diffractograms. Catalytic results demonstrated that ZrO2 addition enhanced the catalytic activity, with increased CO2 conversion up to 13.2 %. The results showed a correlation between catalytic performance and the reducibility of the active metal, driven by the amount of ZrO2 present. The catalyst with the highest ZrO2 loading exhibited the best performance, attributed to its increased surface area and enhanced reducibility. Under optimized conditions (GHSV of 1350 h-1, temperature of 200 degrees C, and pressure of 30 bar), the catalyst achieved 100 % methanol selectivity. This study underscores the significant role of ZrO2 as a promoter in enhancing the activity and selectivity of Cu/MOF-5 catalysts, providing critical insights into the design of efficient catalytic systems for CO2 hydrogenation.