To transduce the temperature-triggered desorption transient into an electrical signal, we propose a thin-film capacitor with a MOF dielectric layer and an ultra-thin, gas-permeable top electrode (Fig. ) . This metal-insulator-metal (MIM) configuration enables high sensitivity due to the exclusion of parasitic substrate contributions to the measured capacitance . At the low VOC concentrations relevant for sensing, the capacitance measured at equilibrium is linearly proportional to the adsorbed quantity of an analyte, regardless of the VOC dielectric constant (SI Fig. ). To illustrate that this relationship holds during out-of-equilibrium measurements, i.e., when the adsorbate distribution is non-uniform over the thickness of the adsorbent film, the response of an equivalent circuit composed of capacitors in series was considered (Fig. ). These simulations reveal only a minor deviation between the capacitance and mass transients (Fig. ). Therefore, using Eq. 1 to fit a measured capacitance transient accurately estimates the analyte diffusivity (errors < 1 %) and the change in adsorbed amount is equal for the heating and cooling steps, is longer than because diffusion is thermally activated. d, Schematic representation of a thin-film capacitor featuring a nanoporous dielectric layer and a gas-permeable top electrode. e, Simulated adsorbate distribution profiles in a nanoporous film with an arbitrary thickness of 1 µm at different time points after initiating desorption.