Abstract Incorporation of MOFs in interfacially polymerized Thin-Film Nanocomposite (TFN) membranes has widely been shown to result in increased membrane performance. However, the exact functioning of these membranes is poorly understood as large variability in permeance increase, filler incorporation and rejection changes can be observed in literature. The synthesis and functioning of TFN membranes (herein exemplified by ZIF-8 filled polyamide (PA) membranes prepared via the EFP method) was investigated via targeted membrane synthesis and thorough characterization via STEM-EDX, XRD and PALS. It is hypothesized that the acid generated during the interfacial polymerization (IP) at least partially degrades the crystalline, acid-sensitive ZIF-8 and that this influences the membrane formation (through so-called secondary effects, i.e. not strictly linked to the pore morphology of the MOF). Nanoscale HAADF-STEM imaging and STEM-EDX Zn-mapping revealed no ZIF-8 particles but rather the presence of randomly shaped regions with elevated Zn-content. Also XRD failed to show the presence of crystalline areas in the composite PA films. As the addition of the acid-quenching TEA led to an increase in the diffraction signal observed in XRD, the role of the acid was confirmed. The separate addition of dissolved Zn2+ to the synthesis of regular TFC membranes showed an increase in permeance while losing some salt retention, similar to observations regularly made for TFN membranes. While the addition of a porous material to a TFC membrane is a straightforward concept, all obtained results indicate that the synthesis and performance of such composite membranes is often more complex than commonly accepted.

中文翻译：

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MOF 在薄膜纳米复合材料 (TFN) 膜中的作用

摘要 在界面聚合薄膜纳米复合材料 (TFN) 膜中加入 MOF 已被广泛证明可提高膜性能。然而，这些膜的确切功能知之甚少，因为在文献中可以观察到渗透性增加、填料掺入和截留率变化的巨大变化。通过靶向膜合成和通过 STEM-EDX、XRD 和 PALS 的彻底表征研究了 TFN 膜（此处以通过 EFP 方法制备的 ZIF-8 填充聚酰胺 (PA) 膜为例）的合成和功能。据推测，界面聚合 (IP) 过程中产生的酸至少部分降解了结晶的、对酸敏感的 ZIF-8，这会影响膜的形成（通过所谓的二次效应，即 与 MOF 的孔形态没有严格关联）。纳米级 HAADF-STEM 成像和 STEM-EDX Zn-mapping 显示没有 ZIF-8 颗粒，而是存在具有升高的 Zn 含量的随机形状区域。XRD 也未能显示复合 PA 膜中存在结晶区域。由于酸淬灭 TEA 的添加导致在 XRD 中观察到的衍射信号增加，因此证实了酸的作用。在常规 TFC 膜的合成中单独添加溶解的 Zn2+ 显示渗透率增加，同时失去一些盐保留，类似于对 TFN 膜进行的常规观察。虽然在 TFC 膜上添加多孔材料是一个简单的概念，