常压下制备二维沸石超薄膜及其气体分离性能研究

Two main challenges for the synthesis of zeolite membrane for gas separation are how to scale up the industrial production of zeolite membranes and how to increase the gas permeability of zeolite membranes, respectively. Aiming at solving the two challenges, this proposal plans to develop a new synthetic route to prepare ultra-thin zeolite membranes under ambient pressure. Detailed plan is exfoliating and dispersing the 2-dimensional zeolites which are of porous structure and nanosheet-like morphology in suspension, then the zeolite nanosheets could be self-assembled on porous substrate to form a self-assembly 2D zeolites film. By coupling the active surface silanol groups of 2D zeolites by direct calcination or chemical reactions under ambient pressure, large and continuous 2D zeolite membranes could be prepared. Their gas separation performance would also be investigated. Main research work of this proposal includes (a) the exfoliation and stabilization of 2D zeolite single layers in suspension and (b) self-assembly of 2D zeolite single layers to ultra-thin zeolite films on porous substrate. The proposal focuses on the mechanism for porous 2D materials self-assembled on porous substrate and the driving force between them. The successful proceeding of this proposal will explain how a kind of 2-dimensinal materials with high-coupling-reaction activity would form an ultra-thin film in a controllable way. The assembly mechanism investigation is theoretically important and of highly novelty. Meanwhile, the ultra-thin zeolite membranes obtained under ambient pressure will show great significance in practical applications.

沸石气体分离膜在工业生产中具有良好的应用前景。当前，沸石气体分离膜面临两个主要挑战：大规模制备沸石膜和提高沸石膜气体分离渗透率。本项目将围绕在常压条件下制备沸石超薄膜开展研究工作。计划利用具有纳米片状形貌的二维沸石材料，将其在溶液中剥离形成单层分散的胶体溶液，在多孔载体表面自组装得到二维沸石自组装膜，再利用二维沸石表面存在的大量活性硅羟基，使自组装膜偶联形成具有良好互生性的二维沸石超薄膜，并对其气体分离性能进行研究。通过实验摸索二维沸石在溶液中形成稳定的单层分散胶体溶液的条件，摸索控制二维沸石自组装膜结构的方法。着重研究二维沸石在多孔载体表面的自组装驱动力和自组装机理。本项目对于这类具有高表面活性的二维材料在多孔载体表面的自组装机理研究具有重要的理论价值，这也是本项目的主要创新之处。同时，开发在常压条件下制备二维沸石超薄膜的路线，对于沸石膜气体分离在实际生产中的应用具有重要意义。

本项目面向高效气体分离多孔膜的制备与性质研究开展研究，尝试基于二维沸石材料的自组装制备超薄沸石气体分离膜，并着重研究二维沸石在多孔载体表面的自组装驱动力和自组装机理。在此思想指导下，对二维沸石的合成，纯化和自组装开展了系统性研究。经研究获得了以下结果：（1）通过选择性破坏三维结构中的特定化学结构能够实现多孔材料从三维结构向二维结构的转变；（2）为了将二维结构转化为单分散的二维材料，我们采用了超声剥离、剪切力剥离、以及机械力剥离等多种方法，实验结果表明这些方法均能够有效地破坏二维无机材料层间相互作用力，为二维无机材料的剥离积累了经验与原始数据；（3）由于二维沸石层间较强的氢键以及电荷相互作用，二维沸石在液相中分散很容易进一步自组装成为多层结构的固体颗粒，阻止其在载体表面自组装形成连续多孔膜。尽管二维沸石气体分离膜的制备存在一定的难度，我们在项目研究进行的过程中也发现了一些新的现象：（1）二维沸石材料由于其表面存在的大量空间上相互分隔的羟基位点，能够为金属催化剂提供良好的负载环境，有利于制备纳米尺寸的金属催化剂；（2）控制二维沸石分散液的挥发过程，可以获得类似于低密度的气凝胶结构，由于其主要成分为二氧化硅，很可能应用于隔热阻燃材料等方面。基于这些发现以及对气体分离性能和催化性能的研究，我们搭建了相关性能研究测试体系，合成了多种多孔材料或多孔材料膜，并对其进行气体分离、催化以及吸附性能的研究，取得了一定的成果。