Cucurbit[6]uril-tuned nanochannels of graphene oxide membrane for enhanced water flux in nanofiltration

Abstract

Graphene oxide (GO) membranes exhibit promising potential in nanofiltration due to their controllable transport channel size and low transport resistance of water molecules, resulting in exceptional water permeability. However, the trade-off between water flux and rejection ratio stemming from tightly packed interlayers poses a challenge to the application of GO membranes in nanofiltration. To overcome this trade-off, a practical method is urgently needed to regulate the interlayer space of GO membranes. In this study, a macrocyclic molecule with a rigid porous structure, cucurbit[6]uril (CB[6]), has been introduced to enlarge and precisely adjust the interlayer distance of GO membranes, effectively addressing the trade-off dilemma. The interlayer distance can be precisely adjusted within a range of 0.46 to 1.35 nm, making it suitable for the removal of small organic molecules from wastewater. Through the optimization of GO and CB[6] quantities, the GO membrane containing 20 µg GO and 49.9 wt% CB[6] (CB6GO-4) demonstrates a high pure water flux (PWF) exceeding 171.3 L m^-2h⁻¹ bar⁻¹, more than 5.9 times higher than a pure GO membrane (28.8 L m^-2h⁻¹ bar⁻¹), alongside a dye rejection ratio over 92 %, indicating the promising potential of CB[6]-intercalated GO membranes in removing organics from industrial saline wastewater.