多孔载体引入同源金属氧化物层诱导形成高稳定金属有机骨架分离膜的设计制备与成膜机理

Nowadays, there still exist some drawbacks for the stability of a MOF membrane and its preparation methods. Thus, in this proposal, a new preparation strategy is designed and used to study the preparation and formation mechanism of a highly stable MOF membrane. The strategy is based on the principle that when the metal oxide layer is made of the same metal as the MOF membrane to be grown, it can produce active sites to induce a uniform nucleation of ZIF nuclei on their surface to initiate and guide the growth of a defect-free ZIF-8 membrane, and also act as an inorganic linker between the porous ceramic substrate and the thin polycrystalline MOF membrane and a modification layer for the porous substrate. Thus, this preparation strategy favors growing a stable and defect-free MOF membrane. It includes a two-step process, that is, first the introduction of a layer of metal oxide on a porous substrate and then the growth of a stable and defect-free MOF membrane which is made of the same metal as the introduced metal oxide layer. The layer of the metal oxide introduced on the substrate plays multifunctional roles such as induction sites, linker and modification in the synthesis of the MOF membrane. With ZIF-8 membrane as typical research representive, the effects of the ZnO layers of different forms including nanoparticles and nanorods on ZIF-8 membrane properties (stability and permeation) and the mechanism of the membrane formation will be investigated. The ZIF-8 membranes with different structures supported on ZnO nanorods grown on the substrates will be designed and prepared by adjusting the morphologies of ZnO nanorods. The formation of other containing zinc ZIF membranes on the ZnO layer as induction introduced on a porous substrate will be also studied. By taking both containing Fe MIL-53 and MIL-101 membranes as the research representives, the induction formation of the membranes on the ferric oxide layers introduced on the substrate will be carried out. The membrane properties will be optimized by adjusting the preparation conditions. It is expected that the mechanism on membrane formation can be clarified. A feasible preparation route for stable MOF membranes and membrane technology can be developed.

针对当今MOF膜稳定性及其相应制膜方法存在的局限性问题，本项目拟提出在多孔载体表面引入具有诱导成核生长点、连接膜层与载体的连接点和修饰载体表面等多功能作用的同源金属氧化物层，诱导合成相应高稳定性MOF分离膜。以ZIF-8膜为典型代表，研究载体表面引入不同结构形式的氧化锌涂层（粒子层和纳米棒层），对诱导合成ZIF-8膜的完整性和稳定性的影响规律及成膜机制；通过设计调控氧化锌棒层微结构形式，构筑合成具有不同结构的'柱支式'和'框架式'高性能ZIF-8膜；以含锌ZIF系列膜(如ZIF-7, 71和78)为代表，研究氧化锌涂层诱导合成相应ZIF系列膜的性能和规律; 以含铁MIL-53和MIL-101膜为代表，研究载体表面引入氧化铁涂层诱导合成相应MOF分离膜的性能和规律。通过研究优化制备条件与成膜性能的关系，揭示同源氧化物诱导成膜机理，开辟一条制备高稳定MOF膜的有效方法和膜分离技术。

针对当今MOF膜稳定性及其相应制膜方法存在的局限性问题，本项目提出在多孔载体表面引入具有诱导成核生长点、连接膜层与载体的连接点和修饰载体表面多功能作用的金属氧化物层，诱导合成了高稳定性MOF分离膜。主要研究结果如下：1）在管式陶瓷载体上，引入ZnO层诱导制备了稳定连续完整的Zn-ZIF系列膜。以大孔粗糙的氧化铝管为载体，通过擦涂法植入ZnO纳米粒子层，诱导合成了高稳定的ZIF-8膜， H2/CH4气体渗透理想分离系数达10以上，具有良好的稳定性和制膜重复性；采用ZnO纳米棒层诱导获得了连续ZIF-7膜、ZIF-8膜和ZIF-14膜，具有更好的制备重复性；并实现了ZIF-8膜合成液重复循环利用。2）引入ZnO纳米粒子层，诱导生长获得了纳米片式结构ZIF膜。利用氨水调节剂的作用，ZnO粒子层可自转化诱导形成连续完整的高性能Zn2(bIm)4纳米片结构式膜，其对双组分H2/CO2气体分离选择性可达50以上，并在250℃下稳定运行100h，具有很高的操作稳定性。在ZnO粒子层上引入一薄层氧化石墨烯（GO）层，利用其限域膜生长可获得高取向Zn2(bIm)4纳米片式膜，其对双组分H2/CO2气体分离选择性接近90。3）运用钴氧化物诱导生长制备了连续完整Co-ZIF-67膜，但钴氧化物比氧化锌更难诱导生长成膜；采用ZnO层诱导生长制备了完整Co-ZIF-67、Co-ZIF-9膜，开辟了非同源氧化物诱导成膜的新途径。4）采用氧化锆纳米粒子层诱导制备了连续UiO-66-NH2膜和晶种涂层诱导法制备了UiO-66膜，并首次应用于渗透蒸发液体模拟汽油脱硫和甲醇/MTBE难分离体系体系，取得了很好的分离效果。.总之，多孔载体表面引入同源氧化物层诱导成膜策略，确实可行。引入的同源氧化物层具有修饰载体、连接膜与载体及诱导成核生长等多功能角色，大大有利于形成连续、稳定完整MOF膜；同时，也发现了非同源氧化物可诱导合成同结构MOF膜，解决了一些常规法难以合成的MOF膜。我们的所有成膜策略均在管式载体上成膜，具有可升级放大特点，因此，真正开辟了一条稳定MOF膜制备的新途径，具有很好的潜在应用前景。