Interlocked graphene oxide provides narrow channels for effective water desalination through forward osmosis.

Unique two-dimensional (2D) water channels formed by stacked graphene oxide (GO) sheets that are 'non-leachable' and non-swellable' can show great potential for water remediation. The interlayer spacing controls the solute or ion sieving and plays a crucial role in water transport in GO based membranes. Herein, the sub nanochannels adjacent to the sheets are altered by either ionic or covalent crosslinking using magnesium hydroxide (Mg(OH)2) and GO quantum dots (GQDs) (named as GOM and G-GQD) respectively. In aqueous solution, these cross-linkers prevent the GO sheets from swelling and precisely controls the interlayer spacing required for un-impeded water permeation. In addition, these narrowed GO sheets facilitated in selective dye rejection, significant improvement in salt rejection of divalent ion by forward osmosis and were observed to be resistive towards bio-fouling and bacterial growth. The crosslinked GO membranes were robust enough to withstand strong cross flow velocity and aided in un-impeded water transport through the nano-channels. Among the membranes, the GQD crosslinked membranes (G-GQD) showed better antifouling characteristics, dye separation performance over 95-97% for various dyes, divalent ion rejection by 97% and no cytotoxicity against HaCaT cells than other GO membranes. Our findings on interlocking the domains of nanoslits of GO structure by small eco-friendly molecules portray these materials as potential candidates for water separation applications.