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

Graphical A facile route is applied to fabricate Zr–TCPP MOFs with incorporated open metal sites M 3+ (Fe 3+ and Al 3+ ) to enhance CO 2 uptake through strong interaction between central M 3+ and CO 2 molecules. Moreover, the CO 2 uptake on Zr–TCPP MOFs with extra Al 3+ ions is higher than that with extra Fe 3+ ions, and is ascribed to the higher isosteric heat of CO 2 adsorption. Developing adsorption materials to capture CO 2 at low pressure has attracted great attention due to the low CO 2 partial pressure in fuel gases. Herein, zirconium-based metal–organic frameworks (PCN-X) are successfully synthesized and open metal sites (Fe 3+ and Al 3+ ) are incorporated into the PCN-X MOFs. The results indicate that the CO 2 adsorption capability is enhanced through the strong interaction between extra open metal centers and CO 2 molecules at low pressure. Meanwhile, the CO 2 adsorption capacity of PCN-X with incorporated Al 3+ is higher than with incorporated Fe 3+ , which can be attributed to the higher isosteric heat of CO 2 adsorption. The adsorption kinetics further indicate the faster CO 2 transmission on PCN-X with extra Al 3+ than with extra Fe 3+ . Besides, modified PCN-X, treated by some inorganic acids, exhibits favorable chemical stability, which is suitable for CO 2 capture from acidic fuel gases.