Extra Unsaturated Metal Centers of Zirconium-Based MOFs: a Facile Approach towards Increasing CO2 Uptake Capacity at Low Pressure

Developing adsorption materials to capture CO2 at low pressure has attracted great attention due to the low CO2 partial pressure in fuel gases. Herein, zirconium-based metal organic frameworks (PCN-X) were successfully synthesized and open metal sites (Fe3+ and Al3+) were incorporated into the PCN-X MOFs. The results indicated that the CO2 adsorption capability was enhanced through the strong interaction between extra open metal centers and CO2 molecule at low pressure. Meanwhile, the CO2 adsorption capacity on PCN-X with incorporated Al3+ was higher than with incorporated Fe3+, which could be attributed to the higher isosteric heat of CO2 adsorption. The adsorption kinetics further indicated the faster CO2 transmission on PCN-X with extra Al3+ than with extra Fe3+. Besides, modified PCN-X was treated by some inorganic acids and exhibited favorable chemical stability, which was suitable for CO2 capture from acidic fuel gases.