Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, MOE), School of Environmental Science and Technology, Dalian University of Technology, Liaoning, 116024, Dalian, China.
William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA.
Nat Commun. 2022 Jan 11;13(1):266. doi: 10.1038/s41467-021-27873-6.
Rational design of high-performance stable metal-organic framework (MOF) membranes is challenging, especially for the sustainable treatment of hypersaline waters to address critical global environmental issues. Herein, a molecular-level intra-crystalline defect strategy combined with a selective layer thinning protocol is proposed to fabricate robust ultrathin missing-linker UiO-66 (ML-UiO-66) membrane to enable fast water permeation. Besides almost complete salt rejection, high and stable water flux is achieved even under long-term pervaporation operation in hash environments, which effectively addresses challenging stability issues. Then, detailed structural characterizations are employed to identify the type, chemical functionality, and density of intra-crystalline missing-linker defects. Moreover, molecular dynamics simulations shed light on the positive atomistic role of these defects, which are responsible for substantially enhancing structural hydrophilicity and enlarging pore window, consequently allowing ultra-fast water transport via a lower-energy-barrier pathway across three-dimensional sub-nanochannels during pervaporation. Unlike common unfavorable defect effects, the present positive intra-crystalline defect engineering concept at the molecular level is expected to pave a promising way toward not only rational design of next-generation MOF membranes with enhanced permeation performance, but additional water treatment applications.
高性能稳定金属-有机骨架（MOF）膜的合理设计具有挑战性，特别是对于可持续处理高盐度水以解决关键的全球环境问题而言。在此，提出了一种基于分子水平的晶内缺陷策略，结合选择性层减薄方案，制备了稳定的超薄缺连接体 UiO-66（ML-UiO-66）膜，以实现快速水渗透。除了几乎完全的盐排斥外，即使在恶劣环境中长期渗透蒸发操作下，也实现了高且稳定的水通量，这有效地解决了具有挑战性的稳定性问题。然后，采用详细的结构特征来识别晶内缺连接体缺陷的类型、化学官能团和密度。此外，分子动力学模拟揭示了这些缺陷的积极原子作用，这些缺陷负责显著增强结构亲水性并扩大孔窗，从而允许通过三维亚纳米通道的超低能垒途径在渗透蒸发过程中实现超快水传输。与常见的不利缺陷效应不同，目前在分子水平上的积极晶内缺陷工程概念有望为不仅设计具有增强渗透性能的下一代 MOF 膜，而且为其他水处理应用铺平道路。
