Abstract:

Metal-organic framework MIL-101(Cr) is a kind of new membrane materials with large pore size and high porosity, which can greatly enhance CO₂ permeability for mixed matrix membranes. However, the blending with MIL-101(Cr) particles will lead to obvious decrease in CO₂ selectivity, mainly caused by the following two reasons: terephthalic acid, as organic legend in MIL-101(Cr), is low in CO₂ affinity relatively; particles after drying for activation, unable to be adequately dispersed in casting solution, would form defects in membranes. In response, two innovative attempts were carried through in this work. At first, amino-MIL-101(Cr) fillers were synthesized with 2-amino-terephthalic acid as organic legend, which could increase solution selectivity. Secondly, the retrofitted technique with MIL-101(Cr) activation after membrane fabrication was utilized to decrease defects caused by particle aggregation. FI-TR characterization revealed that amino-MIL-101(Cr) particles have been synthesized successfully. SEM images demonstrated that both MIL-101(Cr) and amino-MIL-101(Cr) particles can be evenly distributed in mixed matrix membranes through the retrofitted technique. Afterward, the membranes were fabricated with amino-MIL-101(Cr) blended in ethyl cellulose. Gas permeation tests revealed that the optimum particle loading is around 15%(mass). In this case, P_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}} is about 166 barrer (16.5% and 93.0% higher than MIL-101(Cr) blended and pristine membranes, respectively), while {\alpha }_{C{O}_{\mathrm{2}}\text{/}{N}_{\mathrm{2}}} is about 23.9 (25.3% and 17.1% higher than that of MIL-101(Cr) blended and pristine membranes, respectively). On the whole, the blending with amino-MIL-101(Cr) particles through casting-activation approach can significantly enhance CO₂ selective permeation in mixed matrix membranes.

Key words: carbon dioxide, membrane, separation, metal-organic framework, selectivity, permeability

摘要：

金属有机骨架MIL-101(Cr)是大孔径、高孔隙率的新型膜材料，可显著提升混合基质膜的CO₂渗透性，但其掺杂会明显降低选择性，有两方面原因：有机配体的CO₂亲和性较低；填料干燥活化后再分散性差，易团聚形成缺陷。对此，首先以氨基对苯二甲酸为配体合成氨基MIL-101(Cr)，提高溶解选择性，再采用先浇铸-后活化的制膜工艺，减少团聚缺陷。红外测试表明氨基填料成功合成；扫描电镜表明膜中填料分布均匀。掺杂15%(质量)氨基MIL-101(Cr)的乙基纤维素混合基质膜，CO₂渗透系数达到200 barrer，比MIL-101(Cr)膜提高11.2%，较纯聚合物膜提高133.1%；同时，CO₂/N₂选择性达到23.9，比MIL-101(Cr)膜提高25.8%，较纯聚合物膜提高17.1%。综上，采用先浇铸-后活化的制膜工艺掺杂氨基MIL-101(Cr)填料，可同时提高混合基质膜的CO₂渗透性和选择性。

关键词: 二氧化碳, 膜, 分离, 金属有机骨架, 选择性, 渗透系数