基于柔性微囊构筑适用于CO2分离的高通量复合膜

High-flux thin films/membranes with selective gas transport properties have recently triggered growing interdisciplinary interests among separation engineers, material scientists and chemists. 2D inorganic nanosheets have become effective candidates to construct such high-flux membranes. The interlocked layer structure arising from efficient packing of nanosheets contributes the formation of well-defined gas transport pathways and reproducible defect-free structure. Moreover, such a fabrication process also benefits from no pore intrusion and thus high permeation flux. Nevertheless, the existence of multiscale pores in interlocked structures, as well as the complex dependence of gas transport rate on adsorption within nanopores, leads to uncertainty about the gas permeance order, and thus, specially, raises the doubt on reproducible CO2 selectivity. In this project, flexible polymeric microcapsules are selected as building blocks to construct layered membrane, considering their 2D or 2D-like characteristics under pressure difference or their own gravity. The as-prepared membrane is expected to be defect free and pore intrusion free, and the intrinsic permeability and selectivity of capsule wall allow through-plane and selective transport of CO2. As such, CO2-selective, high-flux and defect-free membranes are to be obtained. The microcapsule structures, types of driving force, and composition of suspension-for-membrane will be finely tuned, so as to investigate the mechanism of defects formation and elimination, and to elucidate the possible coupling effects between membrane forming characteristics and gas transport properties. The aims of this project encompass: to develop a novel method of high-flux CO2 separation membrane; to establish the relevant theories for the aforementioned method; and to open novel pathways of membrane CO2 capture intensification.

近年来，气体选择性透过的高通量薄膜成为多学科交叉的前沿热点。基于二维片层无机材料制膜是近年来发展的行之有效的策略。通过片层之间的“互锁式”堆叠，可形成规则有序的传递通道、有效消除缺陷，且无孔渗现象，易获得高通量膜。然而，互锁结构中不同尺度孔道的同时存在，以及在纳米孔道内气体吸附与传递速率的复杂关系，使得气体的优先透过次序具有不确定性，特别是难以确保获得CO2优先透过的膜。本项目采用柔性的高分子微囊为构造单元，利用其在自身重力或压差作用下形成的二维或近二维结构进行堆叠，利用囊壁材料自身的选择透过性传递CO2，以期获得CO2优先透过、高通量、无缺陷的膜。通过调节微囊结构、驱动力类型、制膜液组成等因素，研究微囊堆叠过程中缺陷的形成和修复机制，研究微囊成膜特性和传递特性之间可能存在的耦合规律。拟通过本项目的实施，形成制备高通量CO2分离膜的新方法和新理论，开拓膜法捕碳过程强化的新途径。

二维纳米通道膜（以下简称“二维膜”）是近年来膜技术发展的前沿，但用于CO2分离仍存在传质分离机理不明确、难以实施调控的问题。本项目提出以聚合物微囊替代无机纳米片构筑二维膜的方法，发挥二维膜零孔渗的优势，克服传统二维膜主要依赖筛分机理的问题，同时降低跨层传递的阻力，以更接近溶解-扩散机理的传递方式确保CO2的优先透过和有效分离。探讨了亚微米硅球、碳酸钙微球、蛭石纳米片三种不同模板及其尺寸对成膜性的影响，探讨了沉淀共蒸馏、水相仿生粘合与ATRP三种聚合技术在模板上形成高分子层的不同特点，从而建立了基于聚合物微囊制备二维膜的方法。同时，由于在平行开展的研究工作中，大幅度提升了无机纳米片制备二维膜用于CO2分离的分离性能和可重复性，项目发现在当前技术条件下，超薄纳米片相比于高分子微囊在构筑二维膜方面仍然具有一定优势，调控层间通道较增加跨层通道具有更大的可行性。项目仍在继续提升微囊制备水平，并将构筑单元拓展至二维有机聚合物，综合运用减薄囊壁厚度，面内造孔、改善膜内通道的化学环境等途径，完全实现本项目的学术构想，获得成膜性和分离性能上的同时突破。