Assembly of multidimensional MXene-carbon nanotube ultrathin membranes with an enhanced anti-swelling property for water purification

Severe stacking and swelling properties are critical issues in two-dimensional (2D) lamellar membrane fabrication and separation processes that can result in low flux and poor rejection. Herein, we propose the assembly of multidimensional MXene-carbon nanotube (CNT) ultrathin membranes by loading a MXene intercalated with CNTs onto a tubular ceramic membrane. Benefiting from the modes of van der Waals interactions (hydrogen bond) and repulsion forces between the MXene and functionalized CNTs, the one-dimensional (1D) CNTs are well dispersed and intercalated into the 2D MXene nanosheets, forming a uniform network and continuous three-dimensional (3D) labyrinthine short mass transfer channels, which can considerably improve the permeability and rejection performance of the membranes. Furthermore, the membranes exhibit a distinct suppressed swelling property via a facile thermal crosslinking process (-OH + -OH = -O- + H₂O and -COOH + -OH = -COO + H₂O), accompanied by the formation of new chemical bonds (Ti-O-C and Ti-COO-C) due to dehydroxylation between the neighboring MXene nanosheets and CNTs. Additionally, 50 h long-term operation studies also indicate the promising anti-swelling property and stability of the MXene-CNT membranes. This multidimensional (1D and 2D) assembly and thermal crosslinking strategy represents a new avenue for the facile and scalable development of MXene-based and other 2D material-derived high-performance membranes for water purification.