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

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.

Chemical Vapor Deposition and High-Resolution Patterning of a Highly Conductive Two-Dimensional Coordination Polymer Film.

Crystalline coordination polymers with high electrical conductivities and charge carrier mobilities might open new opportunities for electronic devices. However, current solvent-based synthesis methods hinder compatibility with microfabrication standards. Here, we describe a solvent-free chemical vapor deposition method to prepare high-quality films of the two-dimensional conjugated coordination polymer Cu-BHT (BHT = benzenehexanothiolate). This approach involves the conversion of a metal oxide precursor into Cu-BHT nanofilms with a controllable thickness (20-85 nm) and low roughness (<10 nm) through exposure to the vaporized organic linker. Moreover, the restricted metal ion mobility during the vapor-solid reaction enables high-resolution patterning via both bottom-up lithography, including the fabrication of micron-sized Hall bar and electrode patterns to accurately evaluate the conductivity and mobility values of the Cu-BHT films.

Vapor-Assisted Conversion of Heterobimetallic Titanium-Organic Framework Thin Films.

Heterobimetallic Metal-Organic Frameworks (MOFs) synergically combine the properties of two metal ions, thus offering significant advantages over homometallic MOFs in gas storage, separation, and catalysis, among other applications. However, these remain centered on bulk materials, while applications that require functional coatings on solid supports are not developed. We explore for the first time the deposition of heterometallic Ti-based MOF thin films using vapor-assisted conversion on substrates functionalized with a self-assembled monolayer. Furthermore, metal-induced dynamic topological transformation allows the conversion of MUV-10(Ca) films into MUV-101(Co) and MUV-102(Cu), which is not accessible through direct synthesis, without morphologically altering the films. These nonconventional thin-film deposition techniques enable homogeneous and crystalline coatings of heterometallic titanium MOFs that also maintain their corresponding porosity.