New graphitic carbon nitride-based composite membranes: Fast water transport through the synergistic effect of tannic acid and tris(hydroxymethyl) aminomethane

Graphitic carbon nitride nanosheets can be assembled into two-dimensional layered separation membranes due to their unique structure; however, the narrow interlayer channels (0.32 nm) cause strong transmembrane mass transfer resistance. In this study, we expanded the interlayer spacing by intercalating tris(hydroxymethyl) aminomethane (Tris) molecules as supports while introducing high-affinity and adhesive tannic acid (TA) molecules to suppress the disordered stacking of Tris molecules. The two were stably anchored between the layers through hydrogen bonding to form an interlayer channel of 0.83 nm. While maintaining the high rejection performance (>99%) for EB dyes, the improved composite membrane possessed an ultrahigh water flux (170 ± 6 L h−1 m−2 bar−1) that was more than ten times higher than that of the pristine g-C3N4 membrane. We also studied the acid-base resistance, organic solvent resistance and mechanical stability of the composite membrane.