Co 3 (HCOO) 6 Microporous Metal-Organic Framework Membrane for Separation of CO 2 /CH 4 Mixtures
Résumé
Continuous metal–organic framework‐type Co3(HCOO)6 intergrown films with a one‐dimensional zigzag channel system and pore aperture of 5.5 Å are prepared by secondary growth on preseeded macroporous glass‐frit disks and silicon wafers. The adsorption behavior of CO2 or CH4 single gases on the Co3(HCOO)6 membrane is investigated by in situ IR spectroscopy. It is shown that the isosteric heats of adsorption for CO2 (17.7 kJ mol−1) and CH4 (14.4 kJ mol−1) do not vary with increasing amount of adsorbed gases. The higher value of isosteric heat for CO2 is an indication of the stronger interaction between the CO2 and the Co3(HCOO)6 membrane. The Co3(HCOO)6 membrane is studied by binary gas permeation of CO2 and CH4 at different temperatures (0, 25, and 60 °C). The membrane has CO2/CH4 selectivity with a separation factor higher than 10, which is due to the unique structure and molecular sieving effect. Upon increasing the temperature from 0 to 60 °C, the preferred permeance of CO2 over CH4 is increased from 1.70×10−6 to 2.09×10−6 mol m−2 s−1 Pa−1, while the separation factor for CO2/CH4 shows a corresponding decrease from 15.95 to 10.37. The effective pore size of the Co3(HCOO)6 material combined with the pore shape do not allow the two molecules to pass simultaneously, and once the CO2 molecules are diffused in the micropores, the CH4 is blocked. The supported Co3(HCOO)6 membrane retains high mechanical stability after a number of thermal cycles.