Polyamide-Supported Covalent Organic Framework Nanomembranes for Molecular Size-Dependent Selective Separation
mediaposted on 23.11.2021, 18:05 authored by Yixin Yang, Wende Ma, Guorong Li, Chao Zhong, Xi Yan, Weini Huang, Shasha Zhang, Zongwei Cai, Zian Lin
Membrane-based separation has been demonstrated as an ecofriendly technology in the field of energy and the environment. However, simultaneously enhancing the permeability and selectivity of membranes remains a great challenge due to the lack of a tunable and ordered pore structure. Herein, a facile approach for the interfacial synthesis of polyamide (PA)-supported covalent organic framework (COF) nanomembranes was introduced for the first time, in which interfacial crystallization of COF was formed in a two-phase interface using 1,3,5-triformylphloroglucinol (Tp) and 2,5-diethoxy-terephthalohydrazide (Dth) as building units. The thickness of COF layers covered on a PA substrate ranged from 90 to 550 nm. The as-prepared COF nanomembranes (defined as Tp-Dth/PA) possessed many superior properties, including high porosity, tunable and ordered micropores, and good chemical/mechanical stability. Arising from the synergetic effect of the hydrophilic PA support and highly ordered porous structure of COF layers, the obtained Tp-Dth/PA nanomembranes exhibited outstanding performances in terms of permeability and rejection efficiency, in which the water permeance was up to 31.7 L m–2 h–1 bar–1 and the retention rates for congo red (CR) and alcian blue 8GX (AB) were higher than 99.5 and 99.8%, respectively. Moreover, molecular separation of AB from a mixed aqueous solution was achieved with the Tp-Dth/PA nanomembranes based upon the principle of the size-exclusion effect. In addition, the Tp-Dth/PA nanomembranes could be successfully applied to the selective separation of dyes from industrial wastewater, demonstrating their great potential in water treatment.
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mixed aqueous solutionincluding high porosityalcian blue 8gx8 %, respectivelypa substrate rangedordered pore structurehydrophilic pa supportgreat challenge duepa nanomembranes couldcof layers coveredprepared cof nanomembranescof layersordered microporesgreat potentialwater treatmentwater permeancesynergetic effectsuccessfully appliedsimultaneously enhancingselective separationretention ratesrejection efficiencymolecular separationmembranes remainsmechanical stabilityinterfacial synthesisinterfacial crystallizationindustrial wastewatergood chemicalfirst timefacile approachexclusion effectecofriendly technologycongo redbuilding unitsbased separation7 l550 nm