Gas Sorption Studies of ZIF-7 At High Pressures and Temperatures

Gas sorption measurements in ZIF-7 at pressures up to 100 atm and at temperatures up to 300 °C were made using a high pressure volumetric analyzer.  The isotherms of H₂, CO₂, and N₂ revealed that gas sorption in ZIF-7 increases with increasing temperature.  A maximum sorption capacity for ZIF-7 of 5.5 wt% was measured for H₂ at 100 atm and 300 ^oC, while a 141 wt% sorption capacity was obtained for CO₂ at 50 atm and 300 ^oC.  ZIF-7's sorption capacity for H₂ at 35 ^oC and 100 atm was negligible, but its CO₂ sorption at 35 ^oC and 50 atm was 9 wt% (saturation).  With the exception of this CO₂ result at 35 ^oC, the isotherms did not show pore saturation.  Our findings suggest that the ZIF-7 framework is flexible and may be useful for CO₂ separations.