(280f) Multilayered Covalent Organic Framework Membranes Made By Sequential Interfacial Polymerization for Desalination

Covalent organic frameworks (COFs) possess a range of unique properties including ordered pore structure, tunable pore size and functionality, and excellent stability that make them promising materials for membrane applications. However, most COF membranes reported in the literature exhibited low salt rejections due to their relatively large nanoscale pore diameters (>1 nm). Here, we report the creation of multilayered COF structures in a single membrane with the goal to enhance salt rejections and desalination performance. Multilayered COF membranes with thicknesses below 500 nm were synthesized directly on polymer supports in a matter of seconds via the scalable interfacial polymerization method. Although the membranes formed appear to be amorphous, we have demonstrated that their salt rejections can be tuned and enhanced by engineering the COF-COF interface in the membrane. The misalignment between the distinct 2D COF structures containing different functional group along their pore channels has possibly reduced the effective membrane pore size. As a result, the multilayered COF membranes exhibited salt rejections that are more than 100% higher than those of single-layer COF membranes. Detailed structure characterizations will be combined with effective pore size estimation using neutral solute permeation measurement to understand the mechanism for enhancement in salt rejections.