CO2 Adsorption-Based Separation by Metal Organic Framework (Cu-BTC) versus Zeolite (13X)

The potential for the metal organic framework (MOF) Cu-BTC to selectively adsorb and separate CO2 is considered. Isotherms for CO2, CH4, and N-2 were measured from 0 to 15 bar and at temperatures between 25 and 105 degrees C. The isotherms suggest a much higher working capacity (x4) for CO2 adsorption on Cu-BTC relative to the benchmark zeolite 13X over the same pressure range. Higher CO2/N-2 and CO2/CH4 selectivities in the higher pressure range (1 similar to 15 bar) and with lower heats of adsorption were also demonstrated. Cu-BTC was observed to be stable in O-2 at 25 degrees C, but its crystallinity was reduced in humid environments. The CO2 adsorption capacity was progressively reduced upon cyclic exposure to water vapor at low relative humidity (<30%), but leveled out at 75% of its original value after several water adsorption/desorption cycles.