Selective captivation of DOX via topotactic surface enrichment with hydrated sodium ions on engineered MXene nanosheets

Effective adsorption of the doxorubicin drug from an aqueous system was achieved by utilizing a surfacefunctionalized, two-dimensional transition metal carbide (MXene). Synthesis of the impurity-free parent phase, followed by subsequent etching and alkalization produced the surface-functionalized MXene (Na+-MXene). The powder X-ray diffraction patterns and electron microscopy analysis results suggested that the Na+ ion was successfully intercalated into the two-dimensional MXene with high crystallinity. Xray photoelectron spectroscopy results indicated that an O-rich surface was achieved in the Na+-MXene compared with the conventional MXene, suggesting an enhanced drug adsorption through the O-rich groups. According to the kinetics and isotherm studies, doxorubicin molecules were found to adsorb on Na+-MXene through the pseudo-second-order kinetics, forming a single layer with a maximum adsorption of ∼250 mg g-1. The X-ray photoelectron spectrum after drug adsorption suggested that doxorubicin was either adsorbed by cation exchange- or nucleophilic addition-driven covalent bond formation. Monte Carlo simulation and comparative adsorption studies revealed that the strong affinity of doxorubicin toward Na+-MXene was mainly mediated by the interaction between the primary amino group and the MXene layer, resulting in both cation exchange and covalent bond formation.