Miguel Jaimes, “Continuous Covalent Organic Framework Membranes for Dye/Salt Separation”
Mentors: Xiaoli Ma, Junwei Wang, & Zhiqin Qiang, Materials Science & Engineering
Covalent organic frameworks (COFs) are an emerging class of porous membrane materials constructed from organic building blocks via strong covalent bonds. They possess a wide range of unique properties including high crystallinity, ordered two or three-dimensional pore structure, tunable pore size and functionality, and excellent thermal and chemical stability. With a pore size in the range of 1-3nm, COF membranes are well suited for nanofiltration applications such as the separation of dye molecules. In this work, we will present the synthesis and dye/salt separation properties of COF membranes based on ketoenamine-linked two dimensional (2D) COFs. Their pore structures are constructed by aldehydes and diamines through a Schiff base reaction followed by irreversible enol-keto tautomerism. These 2D COFs can be synthesized as continuous membranes on polymeric substrates using a facile and scalable interfacial crystallization method. In a cross-flow filtration setup, measurements using single dye or salt solution, the membranes showed a high water permeance of >50 L m-2 h-1 bar-1 with a high rejection of dye molecules (e.g., 100% rejection of Congo Red) and low rejection rates (<5%) for mono- and divalent salts (e.g., NaCl and MgSO4). The dye/salt mixture separation properties of these membranes at different separation conditions will also be discussed in this poster presentation.