Hybrid ultrafiltration membranes based on PES and MOFs @ carbon quantum dots for improving anti-fouling performance

Metal organic frameworks (MOFs) have raised considerable interest because of their favorable impacts on the performance of water treatment membranes. Herein, the novel nanocomposite based on both nanoporous MOFs and hydrophilic carbon quantum dots (CQDs) was exploited as a novel dopant for the fabrication of PES ultrafiltration (UF) membranes. CQDs were synthesized via pyrolysis of citric acid, and UiO-66-NH2@CQDs were synthesized via the condensation reactions of CQDs and UiO-66-NH2 using EDC and NHS as the condensating agents. The properties of resulting membranes on the porosity, membrane morphology, hydrophilicity, permeability and anti-fouling performance were adequately investigated. The membranes incorporated with UiO-66-NH2@CQDs exhibited significantly improved water flux (up to 358.5 Lm(-2)h(-1)), which was similar to 1.82 times that of pristine PES membrane. Additionally, the BSA rejections rates for the hybrid membranes were all maintained above 95.0%. Furthermore, the hybrid membranes exhibited enhanced anti-fouling performance and the highest flux recovery ratio (FRR) of the hybrid membrane with 0.5% UiO-66-NH2@CQDs reached 77.6%. The membranes incorporated with UiO-66-NH2@CQDs exhibited better permeability and anti-fouling performance than those incorporated with CQDs or UiO-66-NH2. This work reveals that the novel hydrophilic nanofillers combining CQDs and MOFs exhibit great potential for application in water treatment membranes.