Kara J. Stowers

Ethylene, an essential feedstock for many materials, was produced through ethane oxidative dehydrogenation using a template-derived nickel oxide catalyst. A Ni-based metal-organic framework, Ni-BTC, was used as the template, and catalyst preparation was evaluated by varying calcination time, decomposition environment, and preparation timing. These variables were probed to determine the effect on the reproducibility of the nickel oxide catalyst. Samples were characterized using surface area, X-ray diffraction, and thermogravimetric analysis. Findings indicate that template-derived nickel oxide gives reproducible spent-surface-area-normalized ethylene production, with the RSD error minimized to 3.0% compared to 29.0% for the traditional sol–gel preparation method. The best-performing conditions identified in this study were complete air decomposition for 4 h at 400 °C and limited storage time before catalytic testing. Heating the spent catalyst after the reaction provided insight into the effectiveness of the decomposition environments but did not further improve the air-decomposed samples.

A carbon economy hinges on sustainable treatment and usage of greenhouse gases. Copper-based catalysts are an efficient way to make use of one of the most common greenhouse gases, carbon dioxide. In this work, a metal–organic framework decomposition method was used to synthesize a copper catalyst that was active and reproducible for methanol production via CO₂ hydrogenation. The properties of the as-prepared and decomposed MOF catalysts were analyzed using a wide range of characterization techniques (e.g. SEM, TEM, ICP-MS, XRD, N₂ adsorption, TGA, XPS, H₂-TPR) to rationalize the layer-by-layer synthetic approach to form the subsequent supported Cu nanoparticles. The catalytic performance of the MOF derived catalyst was compared to that of a sol-immobilization prepared Cu/Al₂O₃ catalyst in a fixed-bed continuous flow reactor for CO₂ hydrogenation. The MOF derived catalyst formed from ten iterative layers performed similarly to the sol-immobilization prepared catalyst but displayed increased methanol productivity at all reaction temperatures tested. This work indicates that synthesis of copper-based catalysts through MOF-templating is a viable method that would be impactful for future incorporation of secondary metals such as Zn, Ce, and/or Al that are typical additions for catalytic conversion of CO₂ to methanol.

Metal-organic frameworks (MOFs) have garnered widespread attention due to their inherent tunability and consequent applications for a variety of technologies. Spin-coating is a fast and cost-effective method for new materials discovery, which yields less chemical waste than traditional solvothermal, dip-coating, or other layer-by-layer synthesis methods. The purpose of this work is to expand the types of supported MOF thin films to include a bimetallic thin film and to understand the effects of temperature on the MOF size and coverage, as well as the ranges and limits of composition. Because the pillared MOF archetype M₂(BDC)₂DABCO, where (M = Cu²⁺, Zn²⁺), is known to exist as copper and zinc MOF analogues; therefore, it was chosen for incorporating both metals into a single structure. For the thin films, MOF growth increased with temperature until solution instability (>52 °C). Thin films are sensitive to metal precursor selection; the Zn-MOF thin film would not grow using Zn(NO₃)₂ as the precursor; however, Zn(OAc)₂ resulted in the cogrowth of ZnO nanoparticles within the MOF. The amount of Zn²⁺ incorporated into the Cu-MOF can be changed by altering volume ratios between Cu(NO₃)₂ and Zn(NO₃)₂ precursors in solution. Understanding these parameters for a bimetallic MOF thin film provides a flexible methodology for surface-mounted thin films for future discovery and advancement.

In an interview in 1982, which was 1 year after he shared the Nobel Prize, Kai Siegbahn was asked about his opinion regarding the name of the technique he had developed. Siegbahn had named it “electron spectroscopy for chemical analysis” (ESCA), but the community was choosing to call it “X‐ray photoelectron spectroscopy” (XPS). Now, more than 40 years later, 20 XPS experts have given their opinions on Siegbahn's response and the name of the technique. Some of these participants have been doing XPS for many years and have provided a historical perspective on this issue. While there is no call in these comments for the community to return to “ESCA”—“XPS” is regarded as a more than an adequate name, and insisting on a name change at this point in time would probably only create confusion. However, some of the participants of this study still consider “ESCA” to be an acceptable way to refer to the technique, especially when it is used in a chemical context.

Modifying active species loading, particle size, and distribution on a support is an effective method for tuning catalyst activity. In this work, a copper catalyst anchored on titania was synthesized using the deposition‐precipitation method at low weight % in order to obtain a highly dispersed catalyst ( 1‐Cu/TiO ₂ ). The interactions between the copper and TiO ₂ support contribute to the physical and chemical properties of the catalyst. Transmission electron micrographs indicate copper nanoparticles with ∼2 nm diameter with a fairly uniform distribution across the TiO ₂ particles. This synthetic approach yields a catalyst that is more active than similar precious metal catalysts, and therefore is a possible approach for creating highly efficient catalysts from economic materials.

Metal–Organic Frameworks (MOFs) are an important class of materials that are gaining increasing relevance for many fields including thin films, CO₂ capture, photovoltaics, and catalysts. MOF mediated synthesis (MOFMS) is the decomposition of a MOF to form an amorphous carbon material decorated with metal nanoparticles. MOF thin films are an area where MOFMS has not been thoroughly explored, yet they are likely to be industrially relevant. In this work, we have developed a method for the growth of a copper-based MOF thin film on silicon-based supports. A series of decomposition processes have allowed us to determine which variables can be used to design the final nanoparticle decorated product. These variables include oxygen/nitrogen ratios, the impact of water in atmospheric decomposition, substrate composition, and reduction under hydrogen. A high degree of control over the final thin film product is achieved, with the ability to make a carbon-supported CuO structure with features between 1 and 5 nm, or CuO nanoparticles ranging from 10–500 nm, as well as finely tuned carbon/Cu ratios. Finally, partially reduced samples were obtained and used in the dehydrogenation of ethanol and methanol. Understanding these decomposition variables as applied to supported MOF-thin films will enable development of next generation nanomaterials for use in catalysis.

Metal–organic frameworks (MOFs) have recently emerged as efficient self-sacrificial templates to fabricate porous carbon-supported metal nanoparticles (NPs). Due to observed increased activity, catalysts containing bimetallic NPs represent an active frontier for heterogeneous catalyst development. A strategy to synthesize active catalysts with highly dispersed bimetallic metal/metal oxides within a porous carbon matrix via rapid MOF decomposition using dopants is presented in this paper. A 2,4,6-trinitrotoluene (TNT) additive enhances the rapid thermolysis of the metal-doped Cu-based MOFs to minimize particle aggregation. Catalyst characterization reveals that a secondary metal increases dispersion of both metals over the carbon composite support. The catalyst preparation method influences both the metal particle size and oxidation state. Catalytic performance shows increased rates for 4-nitrophenol reduction even with <1 wt% of added secondary metal. Among the synthesized catalysts, the Ni–CuO@C bimetallic catalyst exhibits outstanding activity. This synthetic strategy is useful for creating highly efficient, robust, non-noble metal catalysts for development of sustainable chemical processes.

Here we address the issue of finding correct CF2/CF3 area ratios from X-ray photoelectron spectroscopy (XPS) C 1s narrow scans of materials containing –CH2CH2(CF2)nCF3, n = 0, 1, 2, …, moieties. For this work, we modified silicon wafers with four different fluorosilanes. The smallest had a trifluoropropyl (n = 0) moiety, followed by nonafluorohexyl (n = 3), tridecafluoro (n = 5), and finally heptadecafluoro (n = 7) moieties. Monolayer deposition of the fluorosilanes was confirmed by spectroscopic ellipsometry (SE), wetting, and XPS. Analysis of the trifluoropropyl (n = 0) surface and a sample of polytetrafluoroethylene provided pure-component XPS spectra for –CF3 and –(CF2)n– moieties, respectively. Initial XPS C 1s peak fitting, which follows Literature precedent, was not entirely adequate. To address this issue, six different fitting approaches with increasing complexity and/or input from Hartree-Fock theory (HF) were considered. Ultimately, we show that by combining HF results with empirical analyses, we obtain more accurate CF2/CF3 area ratios while maintaining high quality fits.