Lignin as a bioderived modular surfactant and intercalant for Ti₃C₂T_x MXene stabilization and tunable functions

Controlled tailoring of atomically thin MXene interlayer spacings by surfactant/intercalants (e.g., polymers, ligands, small molecules) is important to maximize their potential for application. However, challenges persist in achieving precise spacing tunability in a well-defined stacking, combining long-term stability and dispersibility in various solvents. Here, we discovered that lignin can be used as surfactants/intercalants of Ti₃C₂T_x MXenes. The resulting MXene@lignin complexes exhibit superior colloidal stability and oxidation resistance in both water and different organic solvents. More important, we reveal a dynamic interaction between MXene and lignin that enables a wide-range fine interlayer distance tuning at a sub-nanometer scale. Such dynamic interaction is sparse in the reported organic surfactants/intercalants containing single types of functional groups. We also demonstrate the tunability of electrical conductivity, infrared emissivity, and electromagnetic interference shielding effectiveness. Our approach offers a starting point to explore the potential of MXene-biomacromolecule composites for electronics and photonics applications.