Sensitivity enhancement in planar microwave active-resonator using metal organic framework for CO2 detection

• Published in: Sensors and actuators. B, Chemical Vol. 255; pp. 1561 - 1568
• Main Authors: Zarifi, Mohammad H., Gholidoust, Abedeh, Abdolrazzaghi, Mohammad, Shariaty, Pooya, Hashisho, Zaher, Daneshmand, Mojgan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2018
• Subjects: Microwave sensor; MOF; Planar sensor; Zeolith; Microwave sensor; Zeolith; MOF; Planar sensor
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2017.08.169

•A CO2 gas monitoring device based on active microwave planar resonator sensors is present.•Zeolite 13X, and two synthesized MOF-199 (MOF-199-M1 and MOF-199-M2) are studied to demonstrate the effect of material on the sensitivity of the microwave sensor.•The effect of the adsorption capacity of the bed material on the sensitivity of the sensor device is demonstrated. This work presents a proof of concepts of CO2 gas monitoring by a microwave sensor operating in microwave regime and study its sensitivity enhancement using an adsorbent bed of commercially available Zeolite 13X, and two synthesized MOF-199 (MOF-199-M1 and MOF-199-M2). The sensing principle of the sensor is based on the change in the dielectric properties of the bed, in response to CO2 concentration change in the dry CO2/He mixture. The sensor’s response is quantified in terms of change in the resonant frequency with respect to baseline for each material. The sensor shows maximum sensitivity of 24kHz/% CO2 for MOF-199-M2 and minimum of 10kHz/% CO2 for Zeolite 13 X. The sensitivity of the microwave senor to CO2 concentration, with MOF-199-M2 as the bed is higher than MOF-199-M1, which can be related to the presence of different amount of unsaturated Cu2+ ions in their frameworks. XPS and XRD studies revealed marginal structure difference between MOF-199-M1 and MOF-199-M2. MOF-199-M2 has higher adsorption capacity compared to Zeolite 13 X and MOF-199-M1 at CO2 concentration >45 vol.% which demonstrates potential application of microwave sensors even at high CO2 concentration (>45 vol.%) using MOF-199-M2. Further work needs to study the sensor’s performance in non-dry gas streams at different levels of humidity and its integration with different materials to address the practical challenges, and to improve the selectivity of the sensor.