Fabrication And Separation Performance Of Nanoporous Materials Based Mixed Matrix Membranes

Gas separation and water treatment are two important parts of the chemical production and people's life. High efficiency separation technology plays an important role in the separation processes. Membrane based separation technology has proven to be one of the most competitive and potential technologies due to the advantages like energy efficiency, simple operation process and easy scale-up. Currently, polymer membranes and inorganic membranes have been widely studied. While, Polymer membranes are difficult to simultaneously achieve high permeability and selectivity even though they have good processability. Inorganic membrane can achieve high separation performance, but the fabrication of large area membranes without defects is quite challenging. A potential strategy for combing the advantages and overcoming the limites of polymer membranes and inorganic membranes is to create mixed matrix membranes (MMMs) by blending inorganic filler particles into a homogeneous polymer matrix.Nanoporous materials such as metal-organic frameworks (MOFs) and metal-organic polyhedrons (MOPs) exhibit excellent properties such as high porosity, large surface area and highly tunable structures. The research of nanoporous materials based MMMs has become a hotspot aspect. In this paper,we made several systematic studies focused on the design of new MMMs with high efficiency separation performance. The main contents are shown as follows:1?We choice NH2-MIL-101 (Cr) as filler, this material shows high stability, rich finctional groups and large pores, which are helpful for increasing its compatibility with polymer matrix and enhancing the gas separation performance. Polymer of intrinsic microporosity (PIM-1) acts as the polymer matrix, a series of NH2-MIL-101(Cr)/PIM-1 MMMs with different NH2-MIL-101(Cr) loadings were prepared. For C02/N2 separation,the NH2-MIL-101(Cr)/PIM-1 MMM at low NH2-MIL-101(Cr) loading (5 wt %) shows increased gas permeability and selectivity. The C02 permeability was increased 32 % compared with that of the PIM-1 membrane. The reason may be that the large pores of NH2-MIL-101(Cr) can increase the gas pathways in the membrane. Besides, the intrinsic affinity of NH2-MIL-101 (Cr)for CO2 can further facilitate CO2 transport.2?Ionic liquids (ILs) exhibit tunable chemical properties. Some kinds of functionalized ionic liquid, usually called task specific ionic liquid (TSIL), are efficienct in C02 separaiton applications. However, the development of ILs is limited by its high viscosity and easy leakage properties. For MOF based MMMs, the proper modification of MOFs can effectively endow MOFs more unique properties for the membrane separation. Herein, we use MOF as a porous host for TSIL, TSIL as a modifier for MOF, and designed a nanoporous composite material (TSIL@MOF). We further fabricated MMMs with different TSIL@MOF loadings, which showed improved selectivity and permeability for C0Z/N2 separation and successfully breaked the Robeson upper bound. More importantly, this work highly expanded the applications of ILs and proposed a new method to fabricate other advanced membranes.3.For MMMs, the agglomeration and precipitation phenomenons of fillers can seriously decrease the separation performance of MMMs. Therefore,we synthesized functionalized MOP and further prepared MOP based MMMs(MOP/PSF MMMs). The MOP can soluble in the membrane casting solution,thus effectively avoided the agglomeration and precipitation phenomenons of filler in the membrane fabrication processes. Meanwhile, the functional groups of MOP are helpful for gas separation performance. The MMM at the loading of 12 wt % MOP shows effectively increased CO2 permeability and separation factor of CO2/CH4 by 81 % and 60 % compared with those of the pure polymer membrane.4.UiO-66(Zr) with the aperture size of 6.0 A exhibits good hydrophilicity and stability, which are benefit for water purification. We use UiO-66 as filler, polyethersulfone (PES) as polymer matrix and prepared UiO-66/PES MMMs with different UiO-66 loadings. The water purification performance of the membranes was measured. The pure water flux of the UiO-66/PES membrane at 1.0 wt % UiO-66 loading increased by 60 %compared with that of the pure PES membrane, together with increased rejection ratios to organic dyes and antifouling performance.5.Graphene oxide (GO) is considered as a promising filler in composite membranes for water purification due to its excellent hydrophilicity, rich functional groups, etc. To fully make the advantages of GO and endow GO more unique properties, we synthesized UiO-66@GO composite by anchoring UiO-66 to the GO layers. A series of novel composite membranes(UiO-66@GO/MMMs) were prepared by blending UiO-66@GO into PES matrix for water purification. The pure water flux of the UiO-66@GO/PES membrane at 3.0 wt % loading increased by 351 % compared with that of the pure PES membrane, combined with increased rejection ratios to organic dyes and good antifouling performance.