Studying ZIF-8 SURMOF Thin Films with a Langatate Crystal Microbalance: Single-Component Gas Adsorption Isotherms Measured at Elevated Temperatures and Pressures

Abstract

Characterizing the adsorption behavior of thin films at technical operation ranges is highly relevant in order to obtain appropriate experimental parameters, as well as to evaluate their possible integration in multiple applications. Nonetheless, gathering such experimental data is not a trivial task. In the case of metal−organic framework thin films, a particular interesting class of highly porous coatings, determination of adsorption isotherms at elevated temperatures and pressures is not commonly reported. Using a custom designed langatate crystal microbalance following the principle for piezoelectric microbalances, but under harsher conditions, allowed us to present adsorption equilibrium measurements on a zeolitic imidazolate framework 8 (ZIF 8) surface mounted metal−organic framework (SURMOF) thin film at temperatures between 35 and 100°C and at a pressure range up to 10 bars. The layer by layer liquid phase epitaxy approach was used to deposit ZIF 8 SURMOF thin films on langatate crystals. X ray diffraction, infrared reflection absorption spectroscopy, and scanning electron microscopy combined with energy dispersive X ray mapping were used to gather deeper information on the ZIF 8 thin film growth. Single component isotherms were collected for different gases of practical interest, that is, CO 2 , C 2 H 6 , C 2 H 4 , C 3 H 8 , and C 3 H 6 . The measurements were obtained at 35, 50, 75, and 100°C at a gauge pressure range up to 10 bars. The collected data showed a clear preferential adsorption of ethane over ethylene, whereas only a slight difference was found between propane and propylene. Additionally, the experimental data allowed for the determination of adsorption equilibrium constants and saturation loadings of the ZIF 8 material as a thin SURMOF film, which is of great importance for its integration in multiple applications, such as sensor devices or in membrane based separation.

Photoswitchable Metal–Organic Framework Thin Films: From Spectroscopy to Remote-Controllable Membrane Separation and Switchable Conduction

“…SURMOFs are excellent research templates for their controlled thickness, controllable defect density, and homogeneous morphology . The adsorption of important gas molecules such as CO 2 or volatile organic compounds (VOCs) such as hexane and toluene in SURMOFs has been investigated. The amount of molecules adsorbed in MOF films is usually quantified with a quartz crystal microbalance (QCM) (Figure a), which can measure small mass changes with sufficient time resolution. ,, Controllable uptake and release experiments go one step beyond, and the MOF thin film is switched during the experiment.…”

Fast Dynamic Synthesis of MIL-68(In) Thin Films in High Optical Quality for Optical Cavity Sensing

“…The synthesis scheme follows general SURMOF principles but in a continuous manner and is able to work even without retention time. Using an Au-coated quartz crystal microbalance (QCM) sensor as a substrate does allow for direct mass-sensing, ,, and thus allows monitoring the growth in situ .…”

“…Regarding the controlled orientation and crystalline quality of the deposited MOF thin films, the layer-by-layer (LbL) deposition of surface-anchored MOFs (SURMOFs) has shown to yield excellent results. , However, LbL deposition requires careful optimization of reaction parameters, such as the choice of solvent, temperature, and time. As a result, SURMOF fabrication has been reported only for a limited number of MOF compounds, including MOF-2, HKUST-1, layer-pillared systems, ZIF-8, ZIF-67, and UiO-66 . On the other hand, exchanging linkers in those MOFs by following the principles of reticular synthesis and adding different functional moieties to these structures is relatively easily .…”

Fast Dynamic Synthesis of MIL-68(In) Thin Films in High Optical Quality for Optical Cavity Sensing

“…15,16 However, LbL deposition requires careful optimization of reaction parameters, such as the choice of solvent, temperature, and time. As a result, SURMOF fabrication has been reported only for a limited number of MOF compounds, including MOF-2, HKUST-1, layer-pillared systems 17 , ZIF-8 18 , ZIF-67 19 , and UiO-66 20 . On the other hand, exchanging linkers in those MOFs by following the principles of reticular synthesis and adding different functional moieties to these structures is relatively easily.…”

“…The new synthesis scheme follows general SURMOF principles but in a continuous manner and is able to work even without retention time. Using an Au-coated quartz crystal microbalance (QCM) sensor as substrate does allow for direct mass-sensing 17,18,20 , and thus allows monitoring the growth insitu.…”