Covalent organic frameworks (COFs) have evolved into a transformative category of nanofiltration materials due to their intrinsic pore channels and high porosity, sparking a burgeoning interest in fully harnessing the potential of COFs for applications in nanofiltration. Herein, a sandwich structured MXene/COFs membrane was fabricated by the technique of layer-by-layer electrophoretic deposition (LBL EPD), with COFs nanospheres (COFs NPs) serving as the intermediate layer. During the EPD process, controlling the deposition time allows for convenient regulation of each layer's thickness, enabling rapid production of defect-free MXene/COFs membranes. The ultra-thin MXene layer offers excellent film-forming properties for COFs NPs, whereas the intermediate layer of COFs NPs plays a primary sieving function. Moreover, the pore-rich COFs NPs, the ultra-thin MXene layer, and the COFs NPs layer with abundant slits guarantee short and successive mass transport pathways. Under optimal conditions, the MXene/COFs membrane provided a permeance as high as 200.2 L‧m‧h‧bar and a rejection rate of Congo red (CR) as high as 98.9 %. This exceptional performance holds steadfast even within pH ranges of 7–11 and during long-term operation. Meanwhile, MXene/COFs membranes exhibit commendable salt/dye separation performance, achieving an excellent separation factor of 121.1 for NaCl/CR. Moreover, the membrane's exceptional robustness and mechanical strength further facilitate its stable utilization under high transmembrane pressure (1–5 bar). To summarize, MXene/COFs membranes, characterized by their excellent nanofiltration and salt/dye separation performance, highlight the advantages of COFs within the nanofiltration field. This study introduces an innovative alternative approach to designing COFs membranes for highly efficient and high-precision molecular separations.

中文翻译：

---

具有夹层结构的 MXene/COFs 膜，通过逐层电泳沉积快速分离盐/染料


共价有机骨架（COF）由于其固有的孔道和高孔隙率，已发展成为纳滤材料的变革类别，引发了人们对充分利用COF在纳滤应用中的潜力的兴趣。在此，通过逐层电泳沉积（LBL EPD）技术制备了三明治结构的MXene/COFs膜，其中COFs纳米球（COFs NPs）作为中间层。在 EPD 过程中，控制沉积时间可以方便地调节每层的厚度，从而能够快速生产无缺陷的 MXene/COF 膜。超薄MXene层为COFs NPs提供了优异的成膜性能，而COFs NPs的中间层则起到主要的筛分功能。此外，富含孔隙的COFs NPs、超薄MXene层和具有丰富狭缝的COFs NPs层保证了短而连续的传质路径。在最佳条件下，MXene/COFs膜的透过量高达200.2 L·m·h·bar，对刚果红（CR）的截留率高达98.9%。即使在 7-11 的 pH 范围内以及长期运行期间，这种卓越的性能也能保持稳定。同时，MXene/COFs膜表现出值得称赞的盐/染料分离性能，对NaCl/CR实现了121.1的优异分离因子。此外，该膜卓越的坚固性和机械强度进一步促进了其在高跨膜压力（1–5 bar）下的稳定使用。综上所述，MXene/COFs膜以其优异的纳滤和盐/染料分离性能，凸显了COFs在纳滤领域的优势。 这项研究引入了一种创新的替代方法来设计 COF 膜，以实现高效、高精度的分子分离。