Mixed-matrix membranes (MMMs) have received considerable interest because of their capability to synergize polymeric and nanomaterials. Extensive experimental and a handful of simulation studies on MMMs have been conducted for gas separation; however, there is scarce simulation endeavor for liquid separation. Herein, we report an atomic simulation study to examine the swelling of MMMs in water and subsequently explore their performance for water desalination. The MMMs are composed of a polyarylate (coined as “PAR”) and two zeolitic-imidazolate frameworks (ZIF-8 and ZIF-93, respectively) with various PAR/ZIF ratios. After swelling, the bulk region of PAR in different PAR/ZIF MMMs exhibits similar swelling degree and void size distribution, implying the microstructure of PAR is nearly not affected by the presence of ZIF. However, remarkably different behavior at the PAR/ZIF interface is observed between PAR/ZIF-8 and PAR/ZIF-93. It is revealed that hydrophobic ZIF-8 possesses comparable interaction with PAR and water; by contrast, hydrophilic ZIF-93 interacts preferentially with water and negligibly with PAR. Consequently, PAR is compactly packed near the ZIF-8 surface but displaced by water near ZIF-93 surface during swelling process. For water desalination, water permeabilities through the swollen PAR/ZIF-8 MMMs are found to drop with increasing PAR/ZIF-8 ratio due to the blockage of ZIF-8 pores by PAR; intriguingly, water permeabilities through the swollen PAR/ZIF-93 MMMs remain almost unchanged. Moreover, all the MMMs exhibit the capability of complete salt rejection. This simulation study provides molecular insight into the microstructure and performance of PAR/ZIF MMMs, reveals the crucial role of ZIF functionality in the swelling and permeation of PAR/ZIF MMMs, and would facilitate the development of MMMs for high-performance water desalination.

中文翻译：

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聚芳酯/沸石-咪唑酯骨架混合基质膜用于海水淡化的原子模拟研究

混合基质膜（MMMs）由于它们能够协同聚合高分子材料和纳米材料而备受关注。对于气体分离已经进行了广泛的实验和对MMM的一些模拟研究。但是，几乎没有进行液体分离的模拟工作。在此，我们报告了一项原子模拟研究，以检查MMM在水中的溶胀，然后探究其在淡化水中的性能。MMM由具有不同PAR / ZIF比率的聚芳酯（硬币称为“ PAR”）和两个沸石-咪唑酸酯骨架（分别为ZIF-8和ZIF-93）组成。膨胀后，不同PAR / ZIF MMM中PAR的大部分区域表现出相似的膨胀度和空隙尺寸分布，这表明PAR的微观结构几乎不受ZIF的影响。然而，在PAR / ZIF-8和PAR / ZIF-93之间，在PAR / ZIF接口处观察到明显不同的行为。结果表明，疏水性ZIF-8与PAR和水具有可比的相互作用。相比之下，亲水性ZIF-93与水的相互作用优先，而与PAR的相互作用可忽略不计。因此，PAR在ZIF-8表面附近紧密堆积，但在溶胀过程中被ZIF-93表面附近的水置换。对于海水淡化，由于PAR阻塞ZIF-8孔，发现通过膨胀的PAR / ZIF-8 MMM的水渗透率随PAR / ZIF-8比值的增加而降低。有趣的是，通过膨胀的PAR / ZIF-93 MMM的透水率几乎保持不变。此外，所有MMM都具有完全排盐的能力。