Robust and well-structured graphene oxide membranes crosslinked by phenylboronic acid for efficient heavy metal ion...

Graphene oxide (GO) membranes possess a unique laminated structure that enables high selectivity and permeability. However, their separation performance is constrained by irregular nanosheet stacking during fabrication and structural instability caused by membrane swelling. Here, we reported a phenylboronic acid-crosslinked GO (PBA@GO) membrane that leverages covalent B-O-C bonds and π-π stacking to achieve exceptional anti-swelling performance, robust mechanical strength and well-ordered two-dimensional nanochannels for efficient heavy metal ion sieving. The PBA@GO membrane exhibited an Fe³⁺ rejection rate of over 99.2% with a permeance of 238.9 L m^-2 h^-1 bar^-1 (LMH bar^-1), which is four times higher than that of GO membranes. The extremely high rejection rate is mainly attributed to the spatial steric hindrance effect caused by the two-dimensional nanochannels within the membrane. The PBA@GO membrane showed excellent stability across a pH range of 3-12, enhanced tensile strength and sustained high Fe³⁺ rejection (99.2%) with stable water permeance over 24 hours of cross-flow operation. Additionally, the PBA@GO membrane exhibited outstanding rejection rates for other heavy metal ions (above 85%) with water permeances ranging from 187.6 to 203.2 LMH bar^-1. Our work provides a dual-functional crosslinking strategy for GO membranes that simultaneously suppresses swelling and enhances separation performance, enabling efficient water purification.