Three-Dimensional Porous Ti₃C₂T_<i>x</i> MXene-Based Hybrids Formed by Charge-Driven Assembly

Abstract

Functional three-dimensional (3D) structures based on 2D Ti3C2Tx MXene nanosheets are promising candidates for high-performance applications. However, the repulsive electrical double layer forces among MXene nanosheets make their 3D assembly challenging. Herein, we demonstrate that the diffusion of positively charged poly(allylamine hydrochloride) (PAH) into the single-layer MXene suspension allows for a range of free-standing 3D porous structures. The assemblies are developed by the adsorption of PAH chains from an aqueous solution on the MXene surfaces at the interface and their subsequent diffusion into the bulk of MXene suspension. Our morphological analysis shows that an optimum PAH concentration results in smaller and more circular pores. Moreover, 120–200 kDa PAH is found to be more effective than 17.5 kDa in developing MXene assemblies with well-defined pores. A significant change in the porous morphology is observed by manipulating the ionization degrees of the components, illustrating the importance of electrostatic interactions in morphology development. The MXene/PAH hybrids are electroconductive and can be processed into different shapes, including porous fibers that exhibit shape memory properties. Altogether, our results provide a basis for the rational design of hybrid MXene-based macroassemblies with potential applications in electromagnetic shielding, environmental remediation, and tissue engineering.