Affinity layers play a crucial role in chemical sensors for the selective and sensitive detection of analytes. Here, we report the use of composite affinity layers containing Metal Organic Frameworks (MOFs) in a polymeric matrix for sensing purposes. Nanoparticles of NH2-MIL-53(Al) were dispersed in a Matrimid polymer matrix with different weight ratios (0–100 wt %) and drop-casted on planar capacitive transducer devices. These coated devices were electrically analyzed using impedance spectroscopy and investigated for their sensing properties toward the detection of a series of alcohols and water in the gas phase. The measurements indicated a reversible and reproducible response in all devices. Sensor devices containing 40 wt % NH2-MIL-53(Al) in Matrimid showed a maximum response for methanol and water. The sensor response time slowed down with increasing MOF concentration until 40 wt %. The half time of saturation response (τ0.5) increased by ∼1.75 times for the 40 wt % composition compared to devices coated with Matrimid only. This is attributed to polymer rigidificationnear the MOF/polymer interface. Higher MOF loadings (≥50 wt%) resulted in brittle coatings with a response similar to the 100wt % MOF coating. Cross-sensitivity studies showed the ability tokinetically distinguish between the different alcohols with a fasterresponse for methanol and water compared to ethanol and 2-propanol.The observed higher affinity of the pure Matrimid polymer toward methanolcompared to water allows also for a higher uptake of methanol in thecomposite matrices. Also, as indicated by the sensing studies witha mixture of water and methanol, the methanol uptake is independentof the presence of water up to 6000 ppm of water. The NH2-MIL-53(Al) MOFs dispersed in the Matrimid matrix show a sensitiveand reversible capacitive response, even in the presence of water.By tuning the precise compositions, the affinity kinetics and overallaffinity can be tuned, showing the promise of this type of chemicalsensors.
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