Kong Xian, Jiang Jianwen
Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576, Singapore.
Phys Chem Chem Phys. 2017 Jul 19;19(28):18178-18185. doi: 10.1039/c7cp02670f.
Porous organic cages (POCs) have emerged as a new class of porous materials and received considerable interest for their potential applications. Herein we report the first proof-of-concept simulation study on POC membranes for water desalination. Five [4+6] POCs (CC1, CC2, CC3, CC16, and CC17) are considered with similar crystal structures, but different periphery groups and pore morphologies. CC1 is found to be impermeable to water due to disconnected pores. With an interconnected tetrahedral pore network, CC3 and CC16 have an intermediate water permeability of 1-5 × 10 kg m (m h bar). CC2 and CC17 contain straight pores and a widely open pore network, respectively, thus exhibit a high water permeability of 2-3 × 10 kg m (m h bar); nevertheless, salt rejection in CC17 is only 89%. Among the five POC membranes, CC2 is the best for water desalination with performance superior to other membranes reported in the literature. The membrane flexibility is revealed to have a weak effect on water permeation. To provide further microscopic understanding, the permeation duration, diffusion and hydrogen bonding of water in the POC membranes are quantitatively analyzed. From this simulation study, the key factors governing water permeation in the POC membranes are unraveled and CC2 is identified to be an interesting candidate for water desalination.
多孔有机笼（POCs）已成为一类新型多孔材料，并因其潜在应用而受到广泛关注。在此，我们报告了关于用于海水淡化的POC膜的首个概念验证模拟研究。研究考虑了五种具有相似晶体结构，但外围基团和孔形态不同的[4+6] POCs（CC1、CC2、CC3、CC16和CC17）。由于孔不连通，发现CC1对水不可渗透。CC3和CC16具有相互连接的四面体孔网络，其水渗透率为1-5×10 kg m（m h bar），处于中等水平。CC2和CC17分别包含直孔和广泛开放的孔网络，因此表现出2-3×10 kg m（m h bar）的高水渗透率；然而，CC17的脱盐率仅为89%。在这五种POC膜中，CC2是用于海水淡化的最佳选择，其性能优于文献中报道的其他膜。结果表明膜的柔韧性对水渗透的影响较弱。为了提供更深入的微观理解，对水在POC膜中的渗透持续时间、扩散和氢键进行了定量分析。通过这项模拟研究，揭示了控制POC膜中水渗透的关键因素，并确定CC2是海水淡化的一个有吸引力的候选材料。
