Tag Archive for: MOF

Publication on AWSensors technology

Understanding Electrolyte Ion Size Effects on the Performance of Conducting Metal–Organic Framework Supercapacitors

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Authors: Jamie W. Gittins, Kangkang Ge, Chloe J. Balhatchet, Pierre-Louis Taberna, Patrice Simon, Alexander C. Forse

Journal: Journal of the American Chemical Society

Abstract:

Layered metal–organic frameworks (MOFs) have emerged as promising materials for next-generation supercapacitors. Understanding how and why electrolyte ion size impacts electrochemical performance is crucial for developing improved MOF-based devices. To address this, we investigate the energy storage performance of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with a series of 1 M tetraalkylammonium tetrafluoroborate (TAABF4) electrolytes with different cation sizes. Three-electrode experiments show that Cu3(HHTP)2 exhibits an asymmetric charging response with all ion sizes, with higher energy storage upon positive charging and a greater charging asymmetry with larger TAA+ cations. The results further show that smaller TAA+ cations demonstrate superior capacitive performances upon both positive and negative charging compared to larger TAA+ cations. To gain further insights, electrochemical quartz crystal microbalance measurements were performed to probe ion electrosorption during charging and discharging. These reveal that Cu3(HHTP)2 has a cation-dominated charging mechanism, but interestingly indicate that the solvent also participates in the charging process with larger cations. Overall, the results of this study suggest that larger TAA+ cations saturate the pores of the Cu3(HHTP)2-based electrodes. This leads to more asymmetric charging behavior and forces solvent molecules to play a role in the charge storage mechanism. These findings significantly enhance our understanding of ion electrosorption in layered MOFs, and they will guide the design of improved MOF-based supercapacitors.

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Scientific publication

First Direct Gravimetric Detection of Perfluorooctane Sulfonic Acid (PFOS) Water Contaminants, Combination with Electrical Measurements on the Same Device—Proof of Concepts

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Authors: Ivanov, G.R.; Venelinov, T.; Marinov, Y.G.; Hadjichristov, G.B.; Terfort, A.; David, M.; Florescu, M.; Karakuş, S.

Journal: Chemosensors 

Abstract:

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are pollutants of concern due to their long-term persistence in the environment and human health effects. Among them, perfluorooctane sulfonic acid (PFOS) is very ubiquitous and dangerous for health. Currently, the detection levels required by the legislation can be achieved only with expensive laboratory equipment. Hence, there is a need for portable, in-field, and possibly real-time detection. Optical and electrochemical transduction mechanisms are mainly used for the chemical sensors. Here, we report the first gravimetric detection of small-sized molecules like PFOS (MW 500) dissolved in water. A 100 MHz quartz crystal microbalance (QCM) measured at the third harmonic and an even more sensitive 434 MHz two-port surface acoustic wave (SAW) resonator with gold electrodes were used as transducers. The PFOS selective sensing layer was prepared from the metal organic framework (MOF) MIL-101(Cr). Its nano-sized thickness and structure were optimized using the discreet Langmuir–Blodgett (LB) film deposition method. This is the first time that LB multilayers from bulk MOFs have been prepared. The measured frequency downshifts of around 220 kHz per 1 µmol/L of PFOS, a SAW resonator-loaded QL-factor above 2000, and reaction times in the minutes’ range are highly promising for an in-field sensor reaching the water safety directives. Additionally, we use the micrometer-sized interdigitated electrodes of the SAW resonator to strongly enhance the electrochemical impedance spectroscopy (EIS) of the PFOS contamination. Thus, for the first time, we combine the ultra-sensitive gravimetry of small molecules in a water environment with electrical measurements on a single device. This combination provides additional sensor selectivity. Control tests against a bare resonator and two similar compounds prove the concept’s viability. All measurements were performed with pocket-sized tablet-powered devices, thus making the system highly portable and field-deployable. While here we focus on one of the emerging water contaminants, this concept with a different selective coating can be used for other new contaminants.

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Publication on AWSensors technology

Comparison of Thin-Film Capacitor Geometries for the Detection of Volatile Organic Compounds Using a ZIF-8 Affinity Layer

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Authors: Aleksander Matavž, Margot F. K. Verstreken, Jorid Smets, Max L. Tietze, and Rob Ameloot

Journal: ACS Sensors (2023)

 

Abstract

Their chemical diversity, uniform pore sizes, and large internal surface areas make metal–organic frameworks (MOFs) highly suitable for volatile organic compound (VOC) adsorption. This work compares two geometries of capacitive VOC sensors that use the MOF material ZIF-8 as an affinity layer. When using a permeable top electrode (thickness < 25 nm), the metal–insulator–metal (MIM) sandwich configuration exhibits superior sensitivity, an improved detection limit, and a smaller footprint than the conventional interdigitated electrode layout. Moreover, the transduction of VOC adsorption in ZIF-8 via MIM capacitors is more sensitive to polar VOCs and provides better selectivity at high loadings than gravimetric and optical transductions.

 

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Publication on AWSensors technology

Nanoporous Metal–Organic Framework Thin Films Prepared Directly from Gaseous Precursors by Atomic and Molecular Layer Deposition: Implications for Microelectronics

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Authors: Jenna Multia, Dmitry E. Kravchenko, Víctor Rubio-Giménez, Anish Philip, Rob Ameloot, and Maarit Karppinen

Journal: ACS Appl. Nano Mater. (2023)

 

Abstract

Atomic/molecular layer deposition (ALD/MLD) allows for the direct gas-phase synthesis of crystalline metal–organic framework (MOF) thin films. Here, we show for the first time using krypton and methanol physisorption measurements that ALD/MLD-fabricated copper 1,4-benzenedicarboxylate (Cu-BDC) ultrathin films possess accessible porosity matching that of the corresponding bulk MOF.

 

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Publication on AWSensors technology

Aerosol Jet Printing of the Ultramicroporous Calcium Squarate Metal–Organic Framework

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Authors: Dmitry E. Kravchenko, Aleksander Matavž, Víctor Rubio-Giménez, Hanne Vanduffel, Margot Verstreken, Rob Ameloot

Journal: Chem. Mater. (2022)

 

Abstract

Efficient methods to deposit thin layers of metal–organic frameworks (MOFs) are needed to integrate these microporous materials into microelectronics, sensing devices, and membranes. Herein, we report for the first time the direct aerosol jet printing of a MOF material. The ultramicroporous MOF [Ca(C4O4) (H2O)] (UTSA-280) was deposited from an aqueous precursor solution. In addition to blanket coatings, aerosol jet printing provides direct access to patterned coatings with a resolution of 100 μm via a digital, maskless approach. Moreover, by enabling spatial control over the layer thickness via the number of passes of the nozzle, this direct-write approach presents a more accessible alternative to advanced patterning techniques such as grayscale lithography.

 

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