Preparation of nanofibrous metal-organic framework filter for rapid adsorption and selective separation of cationic dye from aqueous solution

Abstract A nanofibrous metal-organic framework (MOF) filter was successfully fabricated via co-electrospinning of anionic bio-MOF-1 (Zn8(Ad)4(BPDC)6O·2(NH2(CH3)2)+, 8DMF, 11H2O) and polyacrylonitrile (PAN) for adsorption and selective separation of cationic dyes from aqueous solution. Characterization with FT-IR, EDS and PXRD confirmed that bio-MOF-1 crystals were effectively encapsulated into PAN nanofibrous matrix and their crystallinity maintained well. Due to the free NH2 (CH3)2+ cations in the channel of bio-MOF-1 and nucleophilic group C≡N in PAN, both bio-MOF-1 crystals and PAN nanofibers were only capable of adsorbing cationic dyes and could not adsorb neutral and anionic dyes. Benefiting from the synergistic effect of bio-MOF-1 and PAN, the bio-MOF/PAN filter exhibited rapid adsorption rate towards positively charged dye methylene blue (MB+), and realized the fast selective separation of MB+ from mixed dyes solution. More importantly, the bio-MOF/PAN filter can be effectively regenerated through ion-exchange process. The adsorption capacities of the filter towards MB+ kept relatively stable values within the five cycles of filtration-regeneration, indicating that bio-MOF/PAN filter can meet the requirement of long service life. This work may provide a new insight into the development of electrospun MOF nanofibrous membrane as a filter for rapid separation and purification of organic dyes from practical wastewater.