Ultrathin two-dimensional materials: New opportunities and challenges in ultra-sensitive gas sensing

The creation and enhancement of gas sensors with exceptional performance are of paramount importance for the rapid and effective identification of hazardous and noxious gases in both production and daily life. At the core of gas sensors are the gas-detecting components. Among the various materials for gas sensing, ultrathin twodimensional (2D) materials offer numerous advantages, such as a large specific surface area, appropriate lattice distortion, an abundance of surface pendant bonds and strong in-plane chemical bonds, making them an ideal platform for gas sensing. This article provides a comprehensive review of the state-of-the-art synthesis techniques and surface-interface electronic structure tuning for ultrathin 2D materials, including transition metal oxides (TMOs), layered transition metal dichalcogenides (TMDs), transition metal carbides, transition metal carbonitrides and nitrides (MXenes), and metal-organic frameworks (MOFs) & covalent organic frameworks (COFs). These materials are used to create gas sensing platforms capable of achieving selective, rapid, and sensitive detection of target gases. The techniques used to improve gas sensors based on ultrathin 2D materials are discussed in detail. Furthermore, the article outlines future challenges and opportunities for the development of efficient ultrathin 2D materials for intelligent and portable gas sensors. We believe that this review will inspire innovative ideas and strategies for the development and design of new gas sensors, shifting the focus from industrial concerns to applied research and scientific issues.