Amino-rich carbon quantum dots ultrathin nanofiltration membranes by double "one-step" methods: Breaking through trade-off among separation, permeation and stability

To coordinate trade-off among separation, permeation and stability, we prepared an amino-rich carbon quantum dots (CQDs-NH2) nanofiltration (NF) membrane with a granular surface structure, an ultra-thin active layer and abundant amine groups by double "one-step" methods (synthesizing CQDs-NH2 by heating of poly-ethylenimine polymer first and then polymerizing trimesoyl chloride (TMC) and CQDs-NH2). Through the in-situ small angle X-ray scattering, we observed that the radius of CQDs-NH2 first decreased slightly and then increased significantly with the heating temperature increasing, and the minimum average radius was 4.64 nm. The optimized conditions of 1.6 wt% CQDs-NH2 solution, 0.2 wt% TMC solution, 60 degrees C curing temperature and 7.5 min curing time were used to prepare polyethersulfone/CQDs-NH2-TMC NF membrane, which exhibited the remarkable performance with permeation flux of 11.98 L.m (2).h (1).bar (1) and SLi,Mg of 14.42. The original interfacial binding force of polyethersulfone/CQDs-NH2-TMC composite membrane was 146.6 mu N, which was two times higher than that of polyethersulfone/poly-ethylenimine-TMC composite membrane due to the "anchor effect" and compatibility. Importantly, during a 120-h continuous filtration, the permeate flux and separation performance were still stable with only small fluctuations, same as the interfacial binding force.