Cucurbit[n]uril-rotaxanes functionalized membranes with heterogeneous channel and regenerable surface for efficient and sustainable nanofiltration

Nanofiltration membranes with high permeability and antifouling ability is favor of efficient and sustainable separation. However, simultaneous enhancement of above performances faces formidable challenges. Herein, we present a facile method to obtain ultrapermeable antifouling nanofiltration membranes via surface binding binary complex of dihydroxyl viologen (HV2+) axis molecule and cucurbit[n]uril (CB[n]) on the freshly prepared polyamide (PA) thin-film composite membranes in a rotaxane manner. CB[n]-rotaxanes feature three-dimensional hydrophilic structure and create heterogeneous channel in PA selective layer, which favors water transport resistance decrease. Meanwhile, CB[n]-rotaxanes as host molecules enhance superficial grafting ability of membranes towards guest-labelled antifouling materials through supramolecular recognition. Inspiringly, adopting stimuli-responsive guest, such as azobenzene, endows grafted antifouling layer with photo-activated regeneration capability, which further improves fouling reversibility of membranes. The optimal membrane exhibits a 3-fold increase of permeance, maintained Na2SO4 rejection and enhanced antifouling properties compared to the pristine, which overmatches most of the state-of-the-art nanofiltration membranes. The proposed construction strategy may pave a novel avenue to develop ultrapermeable antifouling membranes for treating complex wastewater.