共价有机框架材料(COF)作为最有前途的多孔膜材料之一在脱盐领域备受关注，但制备高截盐的COF膜仍具有挑战性。主要是由于COF纳米片自身的固有孔径通常大于水合盐离子直径，且组装成膜过程中容易存在缺陷，严重降低了COF膜的脱盐性能。本研究一方面通过引入磺酸基团，构筑离子型COF纳米片以缩小固有孔径，增强盐离子的排斥；另一方面，利用乙醇辅助自组装过程，得到高纵横比的COF纳米片，以消除膜缺陷，得到完整的COF膜。结合上述策略，所制备的COF膜对Na2SO4的截留率高达98.83%，纯水通量为4.35 L m-2 h-1，并且在高压、酸性或碱性条件下以及高盐浓度下都表现出优异的稳定性。
Abstract
Fabrication of high-rejection covalent organic framework (COF) membranes for desalination remains a significant challenge, due to processing limitations and substrate mismatches. Herein, we report an ethanol-assisted self-assembly strategy for preparing high-rejection COF membranes from anionic TpPa-SO3Na COF (SCOF) nanosheets. This method promotes SCOF dispersion in ethanol with high aspect-ratio structures and elimination of interlayer charge, thus facilitating the formation of defect-free SCOF membranes (COFMs). Furthermore, polyvinyl alcohol (PVA) was used to modify commercial polyethylene (PE) supports ensuring compatibility with the high-rejection SCOF layers. The hydrophilic PVA@PE support with appropriate surface pore induces the SCOF nanosheets to form a complete stacking structure. The resultant COFM (MEtOH) exhibit an impressive Na2SO4 rejection rate of 98.83 % and a pure water flux of 4.35 L m−2 h−1, demonstrate exceptional rejection stability under elevated pressure, acidic or alkaline conditions, and high salt concentrations. The superior desalination performance of the COFMs surpasses the most reported 2D desalination membranes.
Desalination, 2024,118025, https://doi.org/10.1016/j.desal.2024.118025.
水处理技术,2024,50,(6):46-51,62.DOI:10.16796/j.cnki.1000-3770.2024.06.008.