Smart integration of MOFs and CQDs to fabricate defect-free and self-cleaning TFN membranes for dye removal

Abstract

The surface chemistry and functionality of metal-organic frameworks (MOFs) can be manipulated through a judicious choice of integration with other nanomaterials. In this work, heterojunctions of UiO-66-NH2 and carbon quantum dots (CQDs) were prepared to explore their synergetic advantages as nanofillers in thin-film nanocomposite (TFN) membranes for dye removal. The successful integration of UiO-66-NH2/CQD were verified by TEM, FT-IR and XPS. The uniform loading of ultra-small CQDs on the surfaces of UiO-66-NH2 can not only enhance their compatibility with the polyamide matrix, but also promote their photocatalytic oxidation under visible light. Therefore, comparing to the pristine thin-film composite membranes, the optimal TFN membranes embedded with 0.2 wt% of UiO-66-NH2/CQD have demonstrated remarkable improvements in pure water permeance by 89.7% and higher selectivity to dyes of different charges and molecular weights. In addition, the decrease of water flux caused by dye adsorption during the long-term filtration process can be recovered by 92–99% via photocatalytic degradation of the attached dyes within 10 min. This work may offer a new strategy for fabricating defect-free and self-cleaning nanofiltration membranes for dye removal and wastewater reclamation.