Polyimide And Cu₃(BTC)₂ MOF Mixed Matrix Membranes For Gas Separation And Adsorption

A worldwide greenhouse effect and the serious problems of air pollution cause a global concerning. At present, the membrane technique is the one of the most promising gases separation strategies; the key point for the membrane technique is to design and fabricate new efficient membrane. In this study, a kind of metal organic framework material, Cu3(BTC)2 was chosen as inorganic additives, while Polyimide (PI) was chosen as the continuous polymer matrix, a series mixed matrix membrane (MMM) hollow fibers were synthesized, and the permeable performance of various gases were investigated.MOF nanocrystal Cu3(BTC)2 was synthesized and characterized by XRD, SEM and TEM. The results of nitrogen adsorption-desorption showed that the products possessed a high surface area of 1396 m2/g, and contained highly ordered micropores. It had high CO2 adsorption capacity.The images of AFM showed that Cu3(BTC)2 nanocrystals can be highly dispersed into PI matrix without voids. PI-Cu3(BTC)2 MMMs were successfully spun into hollow fiber by the dry/wet-spinning method. The ratio of inorganic additives, the particle size, the spin temperature and pressure, as well as the programmed-temperature imidation proves were investigated to optimize the spin conditions. PI-Cu3(BTC)2 MMM hollow fibers were a kind of in asymmetric membrane. SEM images of the cross-sections revealed the membrane was consisted by surface dense layer, finger-like voids near surface and sponge-like supporting layer. The Cu3(BTC)2 particles were highly dispersed in the surface dense layer and finger-like voids. There was significant plastic deformation of the polymer matrix owing to the strong affinity between the Cu3(BTC)2 and polyimide.The gas permeance, as well as the selectivity of PI-Cu3(BTC)2 MMM hollow fibers were investigated. The separation permeance of various gases was in the sequence of H2> CO2> O2> N2>CH4 which was consisted with the gas molecular dynamic diameter sequence. The H2 permeance was remarkably enhanced as the Cu3(BTC)2 loading increased, while the permeance of other gases were decreased. Hence the selectivity of H2 to the other gases was significantly increased. When Cu3(BTC)2 loading was 6wt%, the permeation of the H2 increased 45% while the ideal selectivity increased 2-3 times compared to pure polyimide.