多层自组装超疏水中空纤维MOF膜及膜接触器

The material properties and porosity of porous membranes are key points in the application of membrane contactors (MC). In order to solve the serious problems of membrane fouling and wetting, as well as to improve the membrane stability and separation performance, novel solvent and thermal resistant hollow fiber MOF membranes with superhydrophobicity will be introduced into MC in this project. First, the phase-inversion or stretching method will be used to prepare polymer hollow fiber membranes (HFMs) with high porosity. The HFMs will be impregnated by precursor solution from metal-organics and subjected to heat-treatment, so the mixed matrix membranes with good solvent and thermal resistance can be obtained. Second, to increase membrane hydrophobicity and reduce membrane resistance, the superhydrophobic metal-organic framework (MOF) crystals prepared by hydrothermal or solvothermal methods will be mixed with different silicanes as coating materials on the above solvent and thermal resistant mixed matrix membranes. The new silicane/MOF composite membranes can be fabricated with low membrane resistance. Finally, to further improve the hydrophobicity of membranes in MC, a continuous, defect free and compact superhydrophobic MOFs layer will be grown on the HFMs. The prepared multi-layer self-assembly MOF membranes will be used as hollow fiber structured packings for distillation of the alcohol/water solution. The resistances on the side of membrane and two fluid phases will be studied. The mechanism of mass transfer will be analyzed, and theoretical model will be established.

本项目从接触器用分离膜的材料特性和微孔性能出发，通过对新型超疏水中空纤维MOF膜的制备研究，为有效解决膜接触器所面临的膜污染和膜润湿问题，提高其分离效率提供新材料新方法。首先，采用拉伸或相转化法制备高孔隙率不同材料的聚合物中空纤维膜，将金属有机化合物配置成无机骨架前驱体，对有机膜进行浸渍和煅烧处理，制备耐热耐溶剂性混合基质膜。其次，采用水（溶剂）热法制备超疏水金属有机骨架材料MOFs颗粒，与不同硅烷共混，对获得的基质膜进行涂覆改性，形成低膜阻的硅烷/MOF复合层。再采用化学接枝法或晶种法进行设计，合成出无缺陷、连续、致密的多层自组装超疏水中空纤维MOF膜。利用所获得的MOF膜，制备高效新型膜结构填料接触器，在醇-水等体系进行精馏分离试验，研究膜侧阻力的分布和变化规律，分析其传递机理，建立相应的数学模型。

本课题首先从分离膜的材料特性和微孔性能出发，对聚丙烯腈、聚偏氟乙烯等聚合物有机膜材料进行杂化、交联或胺化改性设计，制备新型中空纤维MOF膜接触器所需的化学稳定性和热稳定性较强的基膜，打破现有膜接触器在苛刻条件下使用的限制。 其次，立足于金属有机骨架材料MOFs的孔道和结构优势，创新性地通过转化法及原位配体-溶剂热法等，合成出非活化超疏水MOF阵列以及不同拓扑结构、稳定性较高的MOFs材料，使其可以原位转化已合成、易制备的MOF膜为另一种目前不能制备的MOF膜，通过将金属盐固定于转化后的MOFs中以减小MOFs材料的孔径，同时通过暴露合成的晶面，进而提高MOF膜的分离性能。第三，采用高温溶剂热法及金属凝胶法等，制备出不同系列的高硬度MOF /聚合物复合膜。在此基础上，采用MOFs材料作为硅烷的共混介质，大幅减少了现有膜接触器普遍存在的较高跨膜阻力，经醇-水等体系精馏分离试验及传递学分析，优化制备了分离性能优异的新型MOF/PDMS中空纤维复合膜接触器。创新性地研究开发出了一种高效、快速制备超薄MOF膜的方法-凝胶-气相沉积法，在获得连续超薄膜的同时，可以直接放大制备超大有效面积的中空纤维MOF膜接触器，从而有利于实现规模化MOF膜及其器件的制备。