Synthesis and Characterization of Metal-Organic Frameworks Films and their Application as Chemical Sensors
Date
2019-08-08
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Abstract
Metal-organic frameworks (MOFs) are porous crystalline materials composed of metal ions and organic ligands. Recent research displays a growing interest in utilizing MOFs for the potential application of detecting trace gases. This is performed by designing a homogenous thin film of MOFs on a solid substrate attachment. Fabrication of MOFs into thin films present drawbacks, which include long processing times, poor homogeneity, and weak attachment to substrates. In this work, two new synthesis approaches have been developed to overcome the limitations mentioned. These methods of preparation were developed for Cu-BTC, Cu-BDC, ZIF-8 and MOF-5 films on a metal substrate. The metal substrates were chosen to act as a metal ion source by creating a metal hydroxide layer via oxidation, which facilitates the dissolution of metals ions to coordinate with the organic ligands. Intense pulsed light (IPL) and ultrasonic irradiations were used to overcome the activation energy required to initiate the chemical reaction. Both IPL and sonication methods showed good homogeneity, attachment and crystallinity. The IPL film crystal sizes are relatively smaller than the sonicated crystals, this can be contributed to the shorten reaction time of the IPL method (3 min). This study introduces a novel approach to processing MOF films for sensors applied to gas detection. Interestingly, a high-performance hydrogen sensor has been demonstrated by synthesizing a Cu-BTC/polyaniline (PANI) nanocomposite film on a quartz crystal microbalance (QCM) using the IPL method. The selectivity and sensitivity of hydrogen gas on the Cu-BTC film and Cu-BTC/PANI film were compared at room temperature. The Cu-BTC/PANI film showed significantly enhanced results compared to the Cu-BTC film. In addition, a 2 - 5 second response time was achieved while operating at room temperature, showing indifference to high relative humidity (ca. 60%). TiO2-SnO2/MWCNT doped with Cu-BTC was also fabricated using IPL technique for trace ammonia detection. The IPL contributed to the rapid processing time and the thermal conversion of anatase TiO2 to rutile TiO2. The functional film showed a limit of detection of 3.3 ppm. The sensor exhibits reversibility during cyclic testing and minimal drift suggesting that the reaction mechanism is primarily surface adsorption.
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Keywords
sensing, metal-organic frameworks, QCM, nano-composite
Citation
Abuzalat, O. (2019). Synthesis and Characterization of Metal-Organic Frameworks Films and their Application as Chemical Sensors (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.