Defect‐Free Few‐Layer M(4)C(3)T(x) (M = V, Nb, Ta) MXene Nanosheets: Synthesis, Characterization, and Physicochemical Properties

High‐quality few‐layer M(4)C(3)T(x) (M = V, Nb, Ta) MXenes are very important for applications and are necessary for clarifying their physicochemical properties. However, the difficulty in etching for themselves and the existence of MC/MC(1−δ) and M‐Al alloy impurities in their M(4)AlC(3) precursors seriously hinder the achievement of defect‐free few‐layer M(4)C(3)T(x) (M = V, Nb, Ta) MXenes nanosheets. Herein, three different defect‐free few‐layer M(4)C(3)T(x) (M = V, Nb, Ta) nanosheets are obtained by using a universal synthesis strategy of calcination, selective etching, intercalation, and exfoliation. Comprehensive characterizations confirm their defect‐free few‐layer structure feature, large interlayer spacing (1.702–1.955 nm), types of functional groups (–OH, –F, –O), and abundant valance states (M(5+), M(4+), M(3+), M(2+), M(0)). M(4)C(3)T(x) (M = V, Nb, Ta) free‐standing films obtained by vacuum filtration of few‐layer M(4)C(3)T(x) inks show good hydrophilia, high thermostability, and conductivity. A roadmap on synthesis of defect‐free few‐layer M(4)C(3)T(x) (M = V, Nb, Ta) nanosheets are proposed and three key points are summarized. This work provides detailed guidelines for the synthesis of other defect‐free few‐layer MXenes nanosheets, but also will stimulate extensive functional explorations for M(4)C(3)T(x) (M = V, Nb, Ta) MXenes nanosheets in the future.