Ultrastable sandwich graphene oxide hollow fiber membranes with confined interlayer spacing
Graphene oxide (GO) membranes are extremely suitable for ultrafast molecular separation. However, the expansion of the GO interlayer spacing in aqueous solution causes poor rejection of small solutes and the risk of membrane dissociation. We reported a concept of constructing three-dimensional sandwich hollow fibers for confining the interlayer spacing and restraining swelling of GO membranes. Through coating the porous polymer via simple immersion-precipitation phase inversion, GO membranes are sandwiched between the porous coats and hollow fiber substrates. The out-of-plane swelling and interlayer-spacing expansion are suppressed bilaterally by the coats and substrates. Benefiting from the confined interlayer spacing of 0.86 nm, the sandwich GO membranes exhibit large permeance and impressive rejections over 97% and 98% for mono and multivalent salts, which are much higher than those of conventional GO membranes, usually less than 40%. Moreover, the sandwich GO membranes display substantially improved water stability and can maintain the high performance even under ultrasonic treatment.