Covalent organic framework (COF) with azo groups for membranes using interfacial polymerization (IP)

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Covalent organic frameworks (COFs) have captivated the imagination of researchers worldwide for various technological applications. In this work, a new COF with azo linkage (AZO-COF) was successfully synthesized as a bulk material and as a thin layer by interfacial polymerization targeting membrane application. Azo functionality is known to change configuration under light exposure and could provide a membrane combining size selectivity and light response. The AZO-COF chemical and crystal formation was confirmed by spectroscopic techniques (FTIR, XRD and NMR), The interfacial polymerization conditions were optimized to prepare AZO-COF membranes. The thermal characterization of the AZO-COF films was carried out using TGA and DSC to evaluate the thermal behavior of the material. The thickness of the films on porous supports was measured by imaging cross-sectional samples using SEM. Preliminary tests of filtration performance were conducted confirming 70% of rejection of Brilliant Blue (molecular weight 792 g/mol) in methanol. Furthermore, a theoretical investigation of the cis and trans electronic energy levels was conducted in different environments (vacuum and water) using density-functional theory (DFT) and molecular orbital analysis to evaluate properties for applications beyond membranes. While the band gap between HOMO and LUMO levels for the trans configuration in a vacuum is 1.52 eV, in water it increases to 1.68 eV. For the cis AZO-COF, the HOMO-LUMO band gaps in vacuum and water are respectively 1.95 eV and 1.2 eV.

Alshareef, B. S. (2023). Covalent organic framework (COF) with azo groups for membranes using interfacial polymerization (IP) [KAUST Research Repository].


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