Since the proposal of chemical gas sensors in 1962, various gas sensors with diverse functionalities have emerged alongside advancements in gas sensing technology. Due to their compact size, ease of manufacturing, low power consumption, and simple operation, gas sensors are widely used in numerous fields such as disease diagnosis, smart agriculture, environmental monitoring, food quality control, industrial safety, and detection of hazardous or greenhouse gases. Given the complex working environments of gas sensors, particularly in industrial, laboratory, or indoor spaces where multiple gases coexist alongside significant variations in humidity, temperature, and gas concentration, these sensors must meet stringent requirements to effectively detect specific target analytes in terms of sensitivity, selectivity, and stability. Therefore, designing and developing gas sensors with outstanding sensing performance remains a crucial objective, holding significant importance in both fundamental research and practical applications.

Driven by advancements in technologies such as artificial intelligence, the Internet of Things, and nanomaterials, research on chemical sensors has experienced rapid development over the past decade. A growing number of high-response gas sensing instruments have emerged in the market, particularly those capable of effectively detecting target gases at concentrations as low as parts per million (ppm) or parts per billion (ppb). Factors such as the structure and composition of sensors, peripheral electronic devices, and signal processing units (e.g., noise filtering and amplification) significantly influence their sensing performance. Among these, sensing materials serve as the core component of gas sensors, playing a decisive role in sensor performance, especially in terms of sensitivity and selectivity. Ideal sensing materials not only exhibit high responsiveness to low-concentration target analytes but also enable selective detection of specific gases or volatile organic compounds (VOCs) from mixtures. Therefore, the rational design of novel sensing materials with tailored physical and chemical properties for diverse application scenarios is crucial. However, existing gas sensing materials often suffer from issues such as high operating temperatures, low sensitivity, and poor gas selectivity, which limit their practical applications. For instance, traditional metal oxide semiconductors have become the industry standard for commercial gas sensors due to their low cost, simple design, and strong stability; yet their inherent low sensitivity and high operating temperatures constrain their applicability. In contrast, while incorporating noble metals can enhance sensor activity, their scarcity and high costs hinder industrial adoption. Emerging two-dimensional (2D) materials, such as carbides/nitrides, MXenes, transition metal dichalcogenides (TMDs), and graphene, have garnered significant attention as potential gas sensing materials due to their unique surface properties. However, they also face challenges like high synthesis costs, poor stability, and low selectivity toward target gas molecules. Given these challenges, the demand for alternative materials continues to grow, with an urgent need for sensing materials that offer tunable selectivity, high stability, and multifunctional structural design to overcome the limitations of existing materials. As research progresses, an increasing number of porous frameworks have been utilized in the gas sensing field, providing tunable pore structures and chemical environments to enhance selectivity.

In recent years, metal-organic frameworks (MOFs), characterized by tunable properties, permanent porosity, and hybrid inorganic-organic material features, have attracted widespread attention as highly promising sensing materials. Unlike conventional sensing materials, MOFs can achieve tunable topology, porosity, and functionality through diverse organic linkers and metal nodes, while also exhibiting ultra-high specific surface area, catalytic activity, and excellent chemical and thermal stability. These properties endow MOFs with inherent advantages in gas sensing, including programmable pore environments and permanent porosity, enabling pre-enrichment and molecular sieving to achieve high selectivity via size and chemical affinity, while improving sensitivity through low detection limits; dense and periodic binding sites, including accessible metal centers, facilitate specific host-guest interactions and catalytic activation; and adsorption-driven recognition can be combined with electrical, optical, and mass-sensitive readout methods to enable near-room-temperature, low-power operation. From 2012 to 2024, over 10,000 papers (articles and reviews) on MOF-based sensors were published (Figure 1), spanning various disciplines such as industry, biology, chemistry, physics, and materials science. Recent advancements indicate that MOF-based gas sensors not only show great promise in material design and device integration but also point to new directions for enhancing gas sensor performance. The performance of MOF-based sensors is closely related to their morphological structure and sensing methods (e.g., chemiresistive, luminescent, interferometric, and plasmonic resonance), leading to inherent limitations and specific application rules. For instance, MOF powders possess extremely high porosity, specific surface area, and monodisperse metal active sites but require additional encapsulation for gas sensor fabrication, such as direct printing or drop-casting onto ceramic tubes or microelectromechanical system (MEMS) devices, which limits sensor reliability and reproducibility. MOF films offer advantages in gas sensor device integration but face challenges in selectivity and detection limits.Parallel to MOFs, other porous frameworks also play a competitive or complementary role. Covalent organic frameworks (COFs) have ordered pore structures and extended π - conjugated systems, and achieve chemical resistance response and tunable selectivity at room temperature through linker design, metallization, and pore microenvironment control, although device level processing and long-term stability still largely depend on their connection chemistry and polymer interfaces. Hydrogen bonded organic frameworks (HOFs) have been explored for use as porous adsorption layers and molecular filters due to their solvability, self-assembly, and recyclability, and exhibit reversible guest responsive structures; However, compared to the robust metal organic framework (MOF) chemistry, its mechanical and chemical stability as well as device standardization still face challenges. MOF derived porous carbon and metal or oxide composite materials have high conductivity and thermal stability, which can be used for low-power chemical resistance detection. However, they partially sacrifice the crystal structure and site-specific pore chemistry that support inherent selectivity, unless compensated by defect or pore engineering and selective overlay layers. In this context, MOFs have unique advantages due to their combination of coordination unsaturated metal sites and programmable pore chemistry, as well as mature processing and integration routes, which can combine selective adsorption and catalytic activation with electrical and quality sensitive readings. However, limitations in electron transport and humidity tolerance still limit their practical application scope. Based on these advances, a series of innovative MOF based gas sensors, including flexible sensors and microsensors, are constantly being developed. At the same time, MOF materials have also evolved from three-dimensional (3D) structures to planar structures, and from single functionality to multifunctional performance. Therefore, it is crucial to summarize the sensing mechanisms and development prospects of these new MOF based intelligent gas sensors.