Selective Adsorptive Separation of CO2/CH4 and CO2/N-2 by a Water Resistant Zirconium-Porphyrin Metal-Organic Framework

A water resistant zirconium-porphyrin metal-organic framework PCN-222 was synthesized for selectively separating CO2/CH4 and CO2/N-2. Isotherms of CO2, CH4, and N-2 on PCN-222 at low and high pressures were respectively measured. At 298 K, CO2 uptakes at 100 and 3000 kPa were 1.16 and 13.67 mmol/g, respectively. At 298 K and 100 kPa, CO2/CH4 (50:50, v/v) and CO2/N-2 (50:50, v/v) adsorption selectivities separately reached 4.3 and 73.7. At 298 K and 3000 kPa, CO2/CH4 (50:50, v/v) and CO2/N-2 (50:50, v/v) adsorption selectivities were 4.7 and 32.8, respectively. Importantly, breakthrough experiments confirmed that PCN-222 could achieve the effective separation of CO2/CH4 (both 50:50 and 10:90) and CO2/N-2 (both 50:50 and 15:85) gas mixtures. The dynamic regeneration experiments showed that PCN-222 maintained its initial CO2 adsorption capacity after five cycles of CO2 adsorption-desorption. This work suggested that PCN-222 was a potential candidate for selectively separating CO2/N-2 and CO2/CH4.