Fluorine-free and sustainable synthesis of Ti3C2Tx MXene via chelation-assisted alkaline etching for environmental sensing and photothermal applications

Two-dimensional MXene nanosheets have attracted extensive attention due to their exceptional physicochemical properties. However, the conventional synthesis of MXenes relies heavily on hazardous fluoride-based etchants, causing severe environmental and safety risks. Herein, we report a clean, fluorine-free, and sustainable strategy for synthesizing oxygen-terminated Ti 3 C 2 T x MXene (Ff-Ti 3 C 2 T x ) via a novel chelation-assisted alkaline etching approach. By synergistically combining tetramethylammonium hydroxide with ethylenediaminetetraacetic acid, we successfully overcome the intrinsic aluminum-passivation bottleneck that severely restricts the etching efficiency of conventional pure alkaline systems. This dual-agent chelation system not only enables the controlled and efficient delamination of Ti 3 AlC 2 into monolayer Ti 3 C 2 T x nanosheets under extremely mild conditions but also delivers a record-high yield of 40%, representing a 60% improvement over existing fluorine-free methods. The resulting Ff-Ti 3 C 2 T x exhibits a highly hydrophilic, oxygen-rich surface (–OH, –O), which inherently enhances its electrochemical activity and light-harvesting performance. As an environmental sensor, it achieves ultrasensitive detection of p -nitrophenol with a low detection limit of 0.055 μM and a high sensitivity of 3.16 μA μM −1 cm −2 . Moreover, Ff-Ti 3 C 2 T x demonstrates exceptional near-infrared photothermal performance, with a mass extinction coefficient of 21.8 L g −1 cm −1 at 808 nm and a photothermal conversion efficiency of 42.1%. This work provides a scalable, environmentally benign, and high-yielding pathway for fluorine-free production of MXene and establishes Ff-Ti 3 C 2 T x as a versatile platform for next-generation environmental monitoring and sustainable energy applications.