Preparation and ion separation performance of oligoether chains enriched covalent organic framework membrane
The two-dimensional covalent organic framework(COF)membrane material TpOMe-BMTH was prepared on the anodic aluminum oxide(AAO)substrate with 2,5-di-(2-methoxy-methoxy-ethoxy)-phenylmethylhydrazide(BMTH)and 2,4,6-trimethoxy-1,3,5-benzenetricarbaldehyde(TpOMe)condensation based on interfacial polymeriza-tion.The separation properties of the obtained membrane material for lithium and magnesium ions were investigat-ed.Results showed that the TpOMe-BMTH/AAO membranes possessed high crystallization,good stability,and excellent metal ion selectivity,with a separation factor of up to 258 for Li+/Mg2+in a binary salt system consisting of LiCI(0.1 mol·L-1)and MgCl2(0.1 mol·L-1).The plane wave pseudopotential method calculation based on the densi-ty functional theory showed that the binding energy of the oxygen-rich oligoether chains in the material pore for Li+and Mg2+was-282.69 or-13.46 kJ·mol-1.This result means that the obtained membrane has stronger lithium-philic properties and promotes Li+adsorption diffusion along the one-dimensional pore of the COF membrane,finally enabling the efficient separation of lithium and magnesium ions.
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