Au-coated 5 MHz AT-cut QCM sensors (AWSensors) were used. The frequency of the resonance and the bandwidth of the peak (Half-Width at Half Maximum) were recorded for the fundamental frequency, n = 1, and six overtones: n = 3, 5, 7, 9, 11, and 13. The layers were considered rigid, and the Sauerbrey equation was applied to calculate the average and 95 % confidence interval of the specific mass (m, ng cm -2 ) of the layer 32 . All experiments were performed at 24 °C. Equilibrium isotherms were collected by exposing the sensor to a series of stepwise increasing analyte concentrations in a continuously flowing carrier gas N2, covering a concentration range from 0.005 % p/p 0 to 60 % p/p 0 . The total vapor flow was kept constant to avoid effects in the QCM signal due to pressure changes. The equilibrium amount adsorbed of the analyte was calculated from the frequency shift when the signal had stabilized. Transient uptake and release response curves were collected following the frequency shift over time when inducing a concentration shift in the measurement chamber. Kinetic selectivity sensing measurements were performed at 100 kHz using a Keysight E4980AL LCR meter. The measurements were performed in an environmental cell with a temperature-controlled stage (Linkam THFS600E-PB4). A gentle contact to the top electrodes was provided using a thin gold wire (50 µm) glued to the needle probe with silver paint (Leitsilber 200, Ted Pella). The thermal time constant of the setup for a typical heating step from 24 °C to 40 °C was about 6 s (+ /+ =2.5 K s -1 ), which limited the fastest measurable diffusivity to 6 × 10 / 0 m 2 s -1 for a 180 nm film and to 5 × 10 / 2 m 2 s -1 for a 500 nm film (see SI Fig. for more details and bandwidth plots). To approximate the instant T-step in the modeling of kinetic parameters, the diffusion transients were shifted by subtracting the first 3 seconds (thermal time constant, SI Fig. ). In a typical sensing experiment, the sensor was first exposed to pure nitrogen gas until reaching a stable baseline value (' ! . A desired VOC concentration was then introduced in the environmental cell using the VOC supply unit. The kinetic measurements were performed once the sensor signal stabilized, typically by heating from 24 to 40 °C. After the new equilibrium was reached, the reversibility of desorption was evaluated by cooling the sample from 40 to 24 °C. The intrinsic capacitive thermal response of the Au/ZIF-8/Au device, ∆' /' ! = 6 × 10 /0 1/K, measured separately in pure nitrogen, was found to be instantaneous and could readily be compensated for in the sensing experiments (SI Fig. ). For all VOCs, Eq. 1 was used to fit the capacitance transients and extract diffusivities and amplitudes. In the case of water, this approach was not followed because it diffuses several orders of magnitude faster in ZIF-8 than the thermal response of the heater ( = 2 × 10 / m 2 s -1 at 40 °C, corresponding to the time constant of 5.4 × 10 /2 s for 180 nm thick film) . In multi-analyte measurements, the accuracy of the fit improved for larger diffusivity differences between the two components and amplitude ratios closer to one. To assess the impact of the concentration ratio, experiments with a fixed 1-propanol concentration (25 ppm) and varying acetone concentrations (30-580 ppm) were performed. Despite the small difference in diffusivities (6.6 × 10 / 0 m 2 s -1 for acetone and 1× 10 / 0 m 2 s -1 for 1-propanol) and up to a 10-fold difference in amplitude (values for single components), the error in estimated diffusivity and ∆' /' ! values remained below 20 % and 15 %, respectively. VOC supply: VOC vapors were supplied using an in-house built dosing setup. The setup consisted of two mass flow controllers (MFCs, EL-FLOW Bronkhorst). The first MFC delivers a nitrogen carrier flow through a bubbler filled with an analyte to produce the saturated VOC vapor. The second MFC delivers a pure nitrogen stream to dilute the saturated vapor and adjust the vapor concentration to a desired value. The vapor concentration is defined as / ! , where p and ! are the actual and saturated vapor pressure of the analyte, respectively. For dielectric and gravimetric measurements, the bubbler was kept in a thermostatic bath at 21.0 °C, and the sample temperature was 24.0 °C. Hence, the reported p/p 0 is at 24.0 °C and was calculated according to the saturated vapor pressures at bath and sample temperature. The dosing setup reliably produces p/p 0 values between 2-80 %. A dilution module was used for reaching lower concentrations, for which a vapor with / ! = 2.5-5 % was fed into the module and diluted with pure nitrogen by adjusting the gas flows through the MFCs. Binary and ternary mixtures were produced by mixing single-component vapors.