Mechanism-driven gas sensing in MOF and COF materials: bridging adsorption thermodynamics, electronic structure, and signal transduction.
Precise monitoring of nuclear off-gases requires sensing systems that convert molecular adsorption events into reliable, quantifiable signals in complex environments. However, studies of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) remain fragmented, and the links among gas-phase physicochemical properties, adsorption thermodynamics, electronic-structure evolution, and device-level responses are not yet fully understood. Here, a unified, mechanism-driven framework is established to correlate adsorption and signal transduction across multiple scales. The effects of key molecular descriptors, including polarizability, dipole moment, and quadrupole moment, on gas adsorption behaviour in ordered porous frameworks are analysed. Adsorption-driven charge transfer modulates the density of states, Fermi level, and work function, thereby altering carrier concentration and transport properties. The review integrates grand canonical Monte Carlo simulations, density functional theory calculations, machine-learning methods, and in situ or operando spectroscopy to examine correlations among thermodynamic parameters, electronic-structure changes, experimental signatures, and sensing performance. Furthermore, the distinct structural features of MOFs and COFs are discussed within a localisation-delocalisation continuum. The effects of radiation, humidity, and temperature on framework evolution, adsorption behaviour, electronic perturbation, and signal-transduction mode are also discussed. This work provides a unified basis for understanding gas-sensing mechanisms in porous materials and offers guidance for the rational design, experimental validation, and practical deployment of high-performance MOF/COF sensing systems for complex nuclear environments.