Amino-functionalized MXenes for efficient removal of Cr(VI)

[Display omitted] •Amino-functionalized MXene nanosheets are fabricated for Cr(VI) removal.•The NH2-Ti3C2Tx-0.5 nanosheets exhibit the maximum adsorption capacities (107.4 mg/g) for Cr(VI) calculated by Langmuir model.•The NH2-Ti3C2Tx-0.5 nanosheets exhibit high ion selectivity and reusability.•The synergy between Ti3C2Tx and amino group boosts both the adsorption and reduction toward Cr(VI). Amino-functionalized MXenes (NH2-Ti3C2Tx) were constructed with the feature of strong adsorption but also reduction ability for Cr(VI) ions in aqueous solution, via in situ polymerization of (3-aminopropyl)triethoxysilane (APTES) onto the surface of multilayer Ti3C2Tx. Amino groups and Ti3C2Tx nanosheets exhibit synergistic effects in the adsorption and reduction of Cr(VI) anions. The maximum adsorption capacities for Cr(VI) onto NH2-Ti3C2Tx-0.5 calculated by Langmuir model are 107.4 mg/g. Meanwhile, Ti(Ⅱ) species and -NH3+ are individually oxidized into Ti(Ⅳ) species and NO3− during the removal of Cr(VI). The NH2-Ti3C2Tx-0.5 nanosheets exhibit high selectivity and reusability for Cr(VI) removal. Density functional theory calculations illustrate that the synergy between Ti and N remarkably boost the binding energy of MXene toward Cr(VI) along with the electron density on MXene surface. This work provides deep insights into functionalized MXene nanosheets in the fields of heavy metal remediation.