The MMM consisting of ZIF-8 after facile ammonia modification provides excellent separation properties with increases CO2 permeability up to 43% and ideal CO2/CH4 selectivity up to 72% even only 0.5 wt% fillers were embodied.

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Mixed matrix membranes (MMMs) of various properties were prepared for a solvent resistant nanofiltration (SRNF) process by incorporating polyphenylsulfone (PPSU) membranes with self-synthesized copper-1,3,5benzenetricarboxylate (Cu-BTC) nanoparticles at different loadings. Cu-BTC nanoparticles were homogeneously dispersed in PPSU dope solution prior to the casting process, and their subsequent presence in the PPSU membrane was inferred by a combination of FTIR spectroscopy, TGA, SEM, EDX and AFM analyses. These analyses confirmed the existence of Cu-BTC particles and their distribution pattern in the membrane matrix. Membrane performance in organic solvent nanofiltration was evaluated on the basis of methanol permeance and dye-methanol separation. Results showed that membrane pure methanol flux was significantly improved from 102 L m À2 h À1 in the pristine PPSU membrane to >135 L m À2 h À1 in the 3 wt% Cu-BTC incorporated into PPSU membrane when both membranes were tested at 14 bar. Apart from preferential channels created by Cu-BTC, the existence of interfacial voids in MMMs also contributes to the flux improvement owing to the formation of alternative paths for solvent transportation. Results also showed that the membranes incorporated with low loadings of Cu-BTC (ranging between 0.5 and 1.0 wt%) tended to have smaller molecular weight cut-off (MWCO) than that of pristine PPSU and PPSU incorporated with 3 wt% nanoparticles, leading to smaller surface pore size but better separation efficiency. The improvement in membrane flux and dye rejection at low Cu-BTC loadings could be attributed to the good dispersion of the nanoparticles in the membrane matrix coupled with their improved interfacial contact with the membrane. The newly developed membrane also showed a great improvement in terms of resistance to compaction, suggesting Cu-BTC particles are of importance in increasing membrane rigidity and strength.

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In this work, the performances of solvent resistant nanofiltration (SRNF) membranes made of polyphenylsulfone (PPSU) were evaluated with respect to alcohol solvent (methanol, ethanol and isopropanol) flux and dye rejection. The experimental results showed that the solvent flux decreased while dye rejection increased with increasing polymer concentration in the casting solution from 17 wt% to 25 wt%. Apart from molecular size of the solute and viscosity of the solvent, the affinity between the solvent and the membrane was also confirmed to play a significant role in affecting the transport rate of the solvent through the membrane. With respect to the effect of solvent properties and solute size on the dye rejection of solvent-dye mixtures, it was found that the variation of dye rejection is governed by solvent-solute-membrane interactions. The solvent-solute interaction causes the same solute to have different solute size in each tested solvents, whereas the solvent-membrane interaction would result in a change in membrane pore size, leading to different separation efficiency. However, it must pointed out that solvent-membrane interaction is more pronounced compared to solvent-solute interaction, as the dye rejection of ethanol solution is reportedly higher than that of methanol, even though the size of solute in ethanol is smaller compared to its size in methanol.