金属有机框架/聚合物气体分离膜的界面结构设计研究进展

Interfacial manipulation of MOFs/polymer mixed matrix membranes for gas separations:A review

气体分离膜技术在节能减排领域具有突出优势,是一项具有很大发展潜力的气体分离技术.基于金属有机框架/聚合物的混合基质膜兼具聚合物膜材料的易加工性和金属有机框架的优良气体选择吸附特性,受到全球学者的关注.如何有效调控两相界面处微观结构,改善混合基质膜材料的气体分离性能是混合基质膜领域的关键问题.针对这一热点问题,主要综述了近几年学者在金属有机框架/聚合物基混合基质膜的界面结构设计优化、膜材料构效关系研究、膜的规模化制备等领域的研究现状与进展.重点介绍了如何优化与表征界面结构以及金属有机框架与聚合物对膜性能的影响规律两个方面.此外,对混合基质膜材料未来的发展方向进行展望,以期为高性能混合基质膜的理性设计等方面提供研究思路.

Membrane-based separation technology holds great promise to effectively address separation needs in chemical industries due to advantages in energy efficiency,scalability,and small footprint.Mixed matrix membranes based on polymer/metal organic frameworks(MOFs),which combine the ease of processability of polymer materials with the excellent adsorption characteristics of MOFs,have been widely investigated for gas separations.The preparation of gas separation membrane materials with both high flux and gas selectivity is the key to achieving efficient gas separation.Recent research results show that the permeability coefficient and gas pair selectivity of mixed matrix membrane materials are hardly improved simultaneously by adding second phase materials such as MOFs.When the loading of MOFs increases,most membranes have common problems such as particle agglomeration and non-selective interfacial defective structures,which lead to a significant decrease in separation performance.To resolve these issues,research scientists are devoted to tailoring the interfacial microstructure of mixed matrix membranes with an aim to exceed the Robeson upper limit.Many novel characterization techniques coupled with simulation studies were carried out to probe the filler dispersion behavior and interfacial structure within membranes in order to provide rules for rationally designing mixed matrix membranes.A variety of approaches have been proposed to finely tune the interfacial interaction by constructing hydrogen bonding and covalent bonding in the membranes.For example,synthesizing functionalized MOFs via mixed-linker or ligand exchange methods provides a good option to enhance interfacial adhesion within membranes.The amino groups,hydroxyl groups and other organic functional groups in MOFs have the capability to create hydrogen bonding.Moreover,these groups can preferentially adsorb specific gas molecules(such as CO2 molecules)to improve gas selectivity.Some researchers post-functionalized MOFs to graft reactive groups on their surface,incorporating them with cross-linkable polymers.Then the light/heat induced crosslinking reaction occurred within the membrane to seal its defective structure,thereby achieving a substantial improvement in membrane separation performance.The past publications on mixed matrix membranes in the decade demonstrated that the researchers have much more indepth understanding and insights on the fabrication process,membrane morphology,and structure-property relationship of mixed matrix membrane materials.With respect to fundamental research,research scientists are committed to investigating the MOFs properties including crystal morphology,coordinated metal ion,functional groups on membrane performance.To yield high performance mixed matrix membranes,highly permeable polymers were rationally designed as the polymer matrix.However,to complement their widespread industrial application,scale-up of hollow fiber mixed matrix membranes needs to be further investigated.The membrane stability in humid gas feeds is required to be improved.It is also of importance to develop stable,cost-effective and scalable MOFs fillers.With a specific focus on interfacial manipulation of MOFs/polymer mixed matrix membranes for gas separations,this paper mainly reviewed the research progress in the fields of MOFs/polymer-based hybrid matrix membranes for gas separations.It focuses on three aspects:(1)Research progress on optimizing and characterizing the interfacial structure;(2)fundamental understanding of the influences of MOFs and polymers properties on membrane performance;(3)research progress on scale-up of mixed matrix membranes.Finally,the future development direction of mixed matrix membrane materials is proposed in order to provide research ideas for the rational design of high-performance mixed matrix membranes.