Co₃(HCOO)₆ Microporous Metal–Organic Framework Membrane for Separation of CO₂/CH₄ Mixtures

Abstract

Continuous metal-organic framework-type Co(3)(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 CO(2) or CH(4) single gases on the Co(3)(HCOO)(6) membrane is investigated by in situ IR spectroscopy. It is shown that the isosteric heats of adsorption for CO(2) (17.7 kJ mol(-1)) and CH(4) (14.4 kJ mol(-1)) do not vary with increasing amount of adsorbed gases. The higher value of isosteric heat for CO(2) is an indication of the stronger interaction between the CO(2) and the Co(3)(HCOO)(6) membrane. The Co(3)(HCOO)(6) membrane is studied by binary gas permeation of CO(2) and CH(4) at different temperatures (0, 25, and 60 °C). The membrane has CO(2)/CH(4) 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 CO(2) over CH(4) is increased from 1.70×10(-6) to 2.09×10(-6) mol m(-2) s(-1) Pa(-1), while the separation factor for CO(2)/CH(4) shows a corresponding decrease from 15.95 to 10.37. The effective pore size of the Co(3)(HCOO)(6) material combined with the pore shape do not allow the two molecules to pass simultaneously, and once the CO(2) molecules are diffused in the micropores, the CH(4) is blocked. The supported Co(3)(HCOO)(6) membrane retains high mechanical stability after a number of thermal cycles.

Controlling the size and shape of Mg-MOF-74 crystals to optimise film synthesis on alumina substrates

“…M-MOF-74 membranes in literature have higher CH4 permeances than those of CO2 suggesting that the diffusion kinetics of the gases through the MOF cages may determine the separation performance 31 . The performance of M-MOF-74 membranes must be improved to compete with other MOFs such as ZIF-8 10 (CO2 Permeance = 2430 x10 -8 mol m -2 s -1 Pa -1 and CO2/CH4 ideal selectivity = 5.1) and CO3(HCOO)6 16 (CO2 permeance = 225 x10 -8 mol m -2 s -1 Pa -1 and CO2/CH4 ideal selectivity = 5.4). Improved membrane performances could be achieved by further studying the MOF activation parameters and/or post-synthesis modification such as ligand exchange to introduce amine groups to the framework.…”

“…ZIF-8 [10][11][12] , MOF-5 13 , HKUST-1 14,15 etc [16][17][18][19] ) on porous substrates with a clear, definitive MOF layer have been applied to gas separations, overcoming some of the issues associate with MMMs 3 . Typically, these membranes require long syntheses times and multiple steps to produce defect free barriers.…”

Oriented Nano–Microstructure‐Assisted Controllable Fabrication of Metal–Organic Framework Membranes on Nickel Foam

“…In addition, as shown in Figure S10 (Supporting Information), the HKUST-1 membrane with a thickness of 20 µm retains its ideal separation factor and permeance for 24 h. For the mixed gases, the tested separation factor of the binary H 2 /CO 2 through the HKUST-1 membrane with a thickness of 20 µm is 6.8 (with a H 2 permeance of 2.72 × 10 -6 mol m -2 s -1 Pa -1 ), being slightly bigger than the ideal separation factor (6.0). [ 39 ] After heating the vessel at 100 °C for 3 h, a layer with fresh pink color was formed on the Ni foam. Taking Co 3 (HCOO) 6 membrane as an example, the above-made Ni 3 S 2 arrays modifi ed Ni foam was put into a N , N -dimethylformamide (DMF) solution of Co(NO 3 ) 2 and formic acid (FA) in a glass vessel.…”

Pervaporation studies of n-hexane, benzene, mesitylene and their mixtures on zeolitic imidazolate framework-8 membranes

“…This might open new and efficient pathways for membrane productions that are impossible to realize with classical molecular sieves as zeolites. Recently, several groups reported breakthroughs in the preparation of polycrystalline MOF molecular sieve membranes showing selectivity above Knudsen in gas separation experiments [26][27][28][29][30][31][32][33][34][35][36]. However, there are up to now only a few examples utilizing polycrystalline MOF membranes for liquid phase separation by pervaporation [37].…”