Valeriya Chernikova

Insights on Capacitive Interdigitated Electrodes Coated with MOF Thin Films: Humidity and VOCs Sensing as a Case Study

A prototypical metal-organic framework (MOF), a 2D periodic porous structure based on the assembly of copper ions and benzene dicarboxylate (bdc) ligands (Cu(bdc)·xH2O), was grown successfully as a thin film on interdigitated electrodes (IDEs). IDEs have been used for achieving planar CMOS-compatible low-cost capacitive sensing structures for the detection of humidity and volatile organic compounds (VOCs). Accordingly, the resultant IDEs coated with the Cu(bdc)·xH2O thin film was evaluated, for the first time, as a capacitive sensor for gas sensing applications. A fully automated setup, using LabVIEW interfaces to experiment conduction and data acquisition, was developed in order to measure the associated gas sensing performance.

Advanced Fabrication Method for the Preparation of MOF Thin Films: Liquid-Phase Epitaxy Approach Meets Spin Coating Method

Here, we report a new and advanced method for the fabrication of highly oriented/polycrystalline metal-organic framework (MOF) thin films. Building on the attractive features of the liquid-phase epitaxy (LPE) approach, a facile spin coating method was implemented to generate MOF thin films in a high-throughput fashion. Advantageously, this approach offers a great prospective to cost-effectively construct thin-films with a significantly shortened preparation time and a lessened chemicals and solvents consumption, as compared to the conventional LPE-process. Certainly, this new spin-coating approach has been implemented successfully to construct various MOF thin films, ranging in thickness from a few micrometers down to the nanometer scale, spanning 2-D and 3-D benchmark MOF materials including Cu2(bdc)2·xH2O, Zn2(bdc)2·xH2O, HKUST-1, and ZIF-8. This method was appraised and proved effective on a variety of substrates comprising functionalized gold, silicon, glass, porous stainless steel, and aluminum oxide. The facile, high-throughput and cost-effective nature of this approach, coupled with the successful thin film growth and substrate versatility, represents the next generation of methods for MOF thin film fabrication. Therefore, paving the way for these unique MOF materials to address a wide range of challenges in the areas of sensing devices and membrane technology.

Mixed matrix formulations with MOF molecular sieving for key energy-intensive separations

Membrane-based separations can improve energy efficiency and reduce the environmental impacts associated with traditional approaches. Nevertheless, many challenges must be overcome to design membranes that can replace conventional gas separation processes. Here, we report on the incorporation of engineered submicrometre-sized metal–organic framework (MOF) crystals into polymers to form hybrid materials that successfully translate the excellent molecular sieving properties of face-centred cubic (fcu)-MOFs into the resultant membranes. We demonstrate, simultaneously, exceptionally enhanced separation performance in hybrid membranes for two challenging and economically important applications: the removal of CO2 and H2S from natural gas and the separation of butane isomers. Notably, the membrane molecular sieving properties demonstrate that the deliberately regulated and contracted MOF pore-aperture size can discriminate between molecular pairs. The improved performance results from precise control of the linkers delimiting the triangular window, which is the sole entrance to the fcu-MOF pore. This rational-design hybrid approach provides a general toolbox for enhancing the transport properties of advanced membranes bearing molecular sieve fillers with sub-nanometre-sized pore-apertures.Sub-micrometre MOF particles are incorporated into polymers to form mixed matrix membranes. Molecular sieving enables performance far beyond current limits for two applications, butane isomer separation and combined CO2/H2S removal from natural gas.

Nonlinear-Based MEMS Sensors and Active Switches for Gas Detection

The objective of this paper is to demonstrate the integration of a MOF thin film on electrostatically actuated microstructures to realize a switch triggered by gas and a sensing algorithm based on amplitude tracking. The devices are based on the nonlinear response of micromachined clamped-clamped beams. The microbeams are coated with a metal-organic framework (MOF), namely HKUST-1, to achieve high sensitivity. The softening and hardening nonlinear behaviors of the microbeams are exploited to demonstrate the ideas. For gas sensing, an amplitude-based tracking algorithm is developed to quantify the captured quantity of gas. Then, a MEMS switch triggered by gas using the nonlinear response of the microbeam is demonstrated. Noise analysis is conducted, which shows that the switch has high stability against thermal noise. The proposed switch is promising for delivering binary sensing information, and also can be used directly to activate useful functionalities, such as alarming.

A smart microelectromechanical sensor and switch triggered by gas

There is an increasing interest to realize smarter sensors and actuators that can deliver a multitude of sophisticated functionalities while being compact in size and of low cost. We report here combining both sensing and actuation on the same device based on a single microstructure. Specifically, we demonstrate a smart resonant gas (mass) sensor, which in addition to being capable of quantifying the amount of absorbed gas, can be autonomously triggered as an electrical switch upon exceeding a preset threshold of absorbed gas. Toward this, an electrostatically actuated polymer microbeam is fabricated and is then functionalized with a metal-organic framework, namely, HKUST-1. The microbeam is demonstrated to absorb vapors up to a certain threshold, after which is shown to collapse through the dynamic pull-in instability. Upon pull-in, the microstructure can be made to act as an electrical switch to achieve desirable actions, such as alarming.

Zeolite-like Metal–Organic Framework (MOF) Encaged Pt(II)-Porphyrin for Anion-Selective Sensing

The selectivity and sensitivity of sensors are of great interest to the materials chemistry community, and a lot of effort is now devoted to improving these characteristics. More specifically, the selective sensing of anions is one of the largest challenges impeding the sensing-research area due to their similar physical and chemical behaviors. In this work, platinum-metalated porphyrin (Pt(II)TMPyP) was successfully encapsulated in a rho-type zeolite-like metal-organic framework (rho-ZMOF) and applied for anion-selective sensing. The sensing activity and selectivity of the MOF-encaged Pt(II)TMPyP for various anions in aqueous and methanolic media were compared to that of the free (nonencapsulated) Pt(II)TMPyP. While the photoinduced triplet-state electron transfer of Pt(II)TMPyP showed a very low detection limit for anions with no selectivity, the Pt(II)TMPyP encapsulated in the rho-ZMOF framework possessed a unique chemical structure to overcome such limitations. This new approach has the potential for use in other complex sensing applications, including biosensors, which require ion selectivity.

Highly sensitive and selective SO2 MOF sensor: the integration of MFM-300 MOF as a sensitive layer on a capacitive interdigitated electrode

We report on the fabrication of an advanced chemical capacitive sensor for the detection of sulfur dioxide (SO2) at room temperature. The sensing layer based on an indium metal–organic framework (MOF), namely MFM-300, is coated solvothermally on a functionalized capacitive interdigitated electrode. The fabricated sensor exhibits significant detection sensitivity to SO2 at concentrations down to 75 ppb, with the lower detection limit estimated to be around 5 ppb. The MFM-300 MOF sensor demonstrates highly desirable detection selectivity towards SO2vs. CH4, CO2, NO2 and H2, as well as an outstanding SO2 sensing stability.

Metal–Organic Framework Membranes: From Fabrica-Tion to Application in Gas Separation

10 Gas membrane-based separation is considered one of the furthermost effective technology to 11 address energy efficiency and large footprint challenges. Various classes of advanced materials 12 including polymers, zeolites, porous carbons and metal–organic frameworks (MOFs) were 13 attempted as membranes for gas separation. MOFs, among other porous materials, possess uniquely 14 tunable nature, in which the pore size and environment can be controlled by connecting metal ions 15 (or metal ion clusters) with organic linkers with various functionalities. This feature makes them 16 attractive for thin membrane fabrication, as both diffusion and solubility components of 17 permeability can be altered. It is interesting to notice that numerous reports have addressed the 18 synthesis of different MOFs, fabrication of their corresponding thin films and their applications, 19 nonetheless, relatively limited studies addressed their gas separation application as membranes. In 20 this review, we provide a synopsis of the various MOF-based membranes that were fabricated in 21 the last decade. In this review we propose a short introduction touching on the gas separation 22 membrane technology and we shed light on (i) the various techniques developed for the fabrication 23 of MOF as membranes and (ii) challenges and application for MOF thin film membranes in various 24 important gas separation applications. 25

Enabling fluorinated MOF-based membranes for simultaneous removal of H2S and CO2 from natural gas

Membrane-based gas separations are energy efficient processes; however, major challenges remain to develop high-performance membranes enabling the replacement of conventional separation processes. Herein, a new fluorinated MOF-based mixed-matrix membrane is reported, which is formed by incorporating the MOF crystals into selected polymers via a facile mixed-matrix approach. By finely controlling the molecular transport in the channels through the MOF apertures tuned by metal pillars and at the MOF-polymer interfaces, the resulting fluorinated MOF-based membranes exhibit excellent molecular sieving properties. These materials significantly outperform state-of-the-art membranes for simultaneous removal of H2 S and CO2 from natural gas-a challenging and economically important application. The robust fluorinated MOFs (NbOFFIVE-1-Ni, AlFFIVE-1-Ni), pave a way to efficient membrane separation processes that require precise discrimination of closely sized molecules.

Enhanced CO2/CH4 Separation Performance of a Mixed Matrix Membrane Based on Tailored MOF-Polymer Formulations

Abstract Membrane‐based separations offer great potential for more sustainable and economical natural gas upgrading. Systematic studies of CO2/CH4 separation over a wide range of temperatures from 65 °C (338 K) to as low as −40 °C (233 K) reveals a favorable separation mechanism toward CO2 by incorporating Y‐fum‐fcu‐MOF as a filler in a 6FDA‐DAM polyimide membrane. Notably, the decrease of the temperature from 308 K down to 233 K affords an extremely high CO2/CH4 selectivity (≈130) for the hybrid Y‐fum‐fcu‐MOF/6FDA‐DAM membrane, about four‐fold enhancement, with an associated CO2 permeability above 1000 barrers. At subambient temperatures, the pronounced CO2/CH4 diffusion selectivity dominates the high permeation selectivity, and the enhanced CO2 solubility promotes high CO2 permeability. The differences in adsorption enthalpy and activation enthalpy for diffusion between CO2 and CH4 produce the observed favorable CO2 permeation versus CH4. Insights into opportunities for using mixed‐matrix membrane‐based natural gas separations at extreme conditions are provided.