A general way to transform Ti₃C₂T_x MXene into solvent-free fluids for filler phase applications

The emerging two-dimensional transition metal carbides (MXenes) have been gradually coming into the limelight due to excellent mechanical properties, electrical conductivity performance and versatile surface chemistry. However, the oxidation instability and poor processability of MXenes impede further scalable applications. Toward this end, we have for the first time proposed a general and facile strategy to transform Ti₃C₂T_x MXene into a novel class of homogenous, stable solvent-free liquids (MX-fluid) with core-corona-canopy structure via covalent linkage surface engineering strategy. The as-prepared MX-liquid exhibited rather stable antioxidant ability after setting for 540 days. Moreover, the MX-fluid presented macroscopic flow behaviors at room temperature, remarkably improving processability and showing extensive potential in addressing the daunting dispersion issue when blending the Ti₃C₂T_x with other polymer matrixes. Furthermore, the generality of constructing solvent-free MXene fluids using covalent corona-canopy linkage strategy was verified. As two proof-of-concept demonstrations, the MX-fluid was first utilized as a filler phase of mixed matrix membranes (MMMs). The MX-fluid exhibited greatly enhanced CO₂ uptake compared with that of N₂, which was also confirmed by molecular simulation. Next, the MX-fluid was incorporated into Pebax-1657 matrix, and improved CO₂ selective separation (CO₂/N₂ selectivity of 69.2) was obtained, where the CO₂ permeability increased by 179.9% compared with pristine Pebax-1657 membrane. Second, the MX-fluid was demonstrated a good reinforcement phase of epoxy-based composites.