Poly(ionic liquids)-Impregnated UiO-66 composites for efficient sequestration of dichromate

Efficient sequestration of Cr(VI) pollutants from wastewater by metal-organic frameworks (MOFs) remains a great challenge, due to their poor stability and lack of rich anion-exchange sites. To enhance the uptake capacity, kinetics and recyclability of MOFs, a series of imidazolium-based ionic liquids (ILs) were encapsulated into the pores of UiO-66, and then via in situ cross-linking polymerization of ILs, to yield PILs/UiO-66 composites. Of great interest, these positive-charged polymers played the role of anion-exchange sites as inside filler and protective layers as outside coating of UiO-66. As a result, the top optimized composites exhibited outstanding stability (pH ​= ​0), fast sorption kinetics (within 1 ​min), superior uptake capacity (787 ​mg ​g−1, 5 times of UiO-66), high distribution coefficient (1.7 ​× ​105 ​mL ​g−1-, 4276 times of UiO-66), and good recyclability (>10 cycles), in the sequestration of dichromate from water solution. This established strategy provided a universal approach to promote the MOFs-based sorbents in sequestration of anion pollutants.