Two-Dimensional Titanium Carbides (Ti(3)C(2)T(x)) Functionalized by Poly(m-phenylenediamine) for Efficient Adsorption and Reduction of Hexavalent Chromium

Titanium carbides (MXenes) are promising multifunctional materials. However, the negative surface charge and layer-by-layer restacking of MXenes severely restrict their application in the field of anionic pollutants, including in hexavalent chromium (Cr(VI)). Herein, Ti(3)C(2)T(x) MXenes was functionalized through in situ polymerization and intercalation of poly(m-phenylenediamine) (PmPD), then Ti(3)C(2)T(x)/PmPD composites were obtained. Delightedly, Ti(3)C(2)T(x)/PmPD composites exhibited positive surface charge, expanded interlayer spacing, and enhanced hydrophobicity. Furthermore, the specific surface area of Ti(3)C(2)T(x)/PmPD composite was five and 23 times that of Ti(3)C(2)T(x) and PmPD, respectively. These advantages endowed Ti(3)C(2)T(x)/PmPD composite with an excellent adsorption capacity of Cr(VI) (540.47 mg g(−1)), which was superior to PmPD (384.73 mg g(−1)), Ti(3)C(2)T(x) MXene (137.45 mg g(−1)), and the reported MXene-based adsorbents. The Cr(VI) removal mechanism mainly involved electrostatic adsorption, reduction, and chelation interaction. This study developed a simple functionalization strategy, which would greatly explore the potential of MXenes in the field of anionic pollutants.