Temperature-Dependent Nitrous Oxide/Carbon Dioxide Preferential Adsorption in a Thiazolium-Functionalized NU-1000 Metal-Organic Framework

Solvent-assisted ligand incorporation (SALI) of the ditopic linker 5-carboxy-3-(4-carboxybenzyl)thiazolium bromide [(H2PhTz)Br] into the zirconium metal-organic framework NU-1000 [Zr6O4(OH)8(H2O)4(TBAPy)2, where NU = Northwestern University and H4TBAPy = 1,3,6,8-tetrakis(p-benzoic-acid)pyrene], led to the SALIed NU-1000-PhTz material of minimal formula [Zr6O4(OH)6(H2O)2(TBAPy)2(PhTz)]Br. NU-1000-PhTz has been thoroughly characterized in the solid state. As confirmed by powder X-ray diffraction, this material keeps the same three-dimensional architecture of NU-1000 and the dicarboxylic extra linker bridges adjacent [Zr6] nodes ca. 8 Å far apart along the crystallographic c-axis. The functionalized MOF has a BET specific surface area of 1560 m2/g, and it is featured by a slightly higher thermal stability than its parent material (Tdec = 820 vs. 800 K, respectively). NU-1000-PhTz has been exploited for the capture and separation of two pollutant gases: carbon dioxide (CO2) and nitrous oxide (N2O). The high thermodynamic affinity for both gases [isosteric heat of adsorption (Qst) = 25 and 27 kJ mol-1 for CO2 and N2O, respectively] reasonably stems from the strong interactions between these (polar) "stick-like"molecules and the ionic framework. Intriguingly, NU-1000-PhTz shows an unprecedented temperature-dependent adsorption capacity, loading more N2O in the 298 K ≤ T ≤ 313 K range but more CO2 at temperatures falling out of this range. Grand canonical Monte Carlo simulations of the adsorption isotherms confirmed that the preferential adsorption sites of both gases are the triangular channels (micropores) in close proximity to the polar pillar. While CO2 interacts with the thiazolium ring in an "end-on"fashion through its O atoms, N2O adopts a "side-on"configuration through its three atoms simultaneously. These findings open new horizons in the discovery of functional materials that may discriminate between polluting gases through selective adsorption at different temperatures

Calidad fisiológica de semillas de maní (Arachis hypogaea L.) con distintos grados de madurez

El objetivo de este trabajo fue establecer para las condiciones de cultivo de maní en Córdoba (Argentina) qué incidencia tiene la madurez de los frutos sobre la calidad de las semillas que se encuentran en su interior, a fin de especificar qué porcentaje de maduración es el óptimo para la cosecha cuando el destino es la producción de semillas. Se utilizaron frutos producidos bajo condiciones hídricas diferentes, que fueron clasificados de acuerdo a su madurez. Se determinó el perfil de maduración y el peso seco de las semillas de cada grado de madurez.Las semillas de los grados de madurez 2, 3, 4, 5, 6 y 7 fueron sometidas a las pruebas de germinación estándar, peso medio de plántulas y envejecimiento acelerado. El cultivo sin limitantes hídricas aumentó la proporción de frutos maduros.No hubo incidencia del grado de maduración sobre la germinación estándar de las semillas, pero sí ligeramente sobre la germinación luego de ser sometidas a envejecimiento acelerado. El peso medio de plántulas sin sus cotiledones fue marcadamente afectado por la madurez de las semillas

Metal-Organic Frameworks as Heterogeneous Catalysts in Hydrogen Production from Lightweight Inorganic Hydrides

© 2017 American Chemical Society. Ammonia-borane (NH 3 ·BH 3 , AB), hydrazine (NH 2 NH 2 ), lithium borohydride (Li(BH 4 )), and sodium alanate (Na(AlH 4 )) are popular chemical hydrogen storage inorganic solid materials featuring high gravimetric hydrogen contents (H wt %) and remarkable stability under ambient conditions. Ultrapure H 2 is formed from these compounds either via pyrolysis (i.e., a simple material heating) or via hydrolysis (chemical reaction with water). In both cases, a series of homogeneous and heterogeneous catalysts have been designed to assist the process. Among the latter, metal-organic frameworks (MOFs, crystalline 3D porous lattices made of metallic nodes and organic polytopic linkers) have rapidly emerged as versatile candidates for this role. The nanoconfinement of lightweight hydrides in MOFs produces a "hydride@MOF" composite material. Hydride coordination to MOF exposed metal sites or its reaction with functional groups on the organic linkers facilitates the thermal decomposition, lowering the hydrogen release temperature and increasing the hydrogen production rate. For hydrolysis, MOFs are used as templates for the preparation of metal(0) nanoparticles (NPs) uniformly distributed in their inner cavities through a preliminary impregnation with a solution containing a metal salt followed by reduction. The "NPs@MOF" are the real active species that catalyze the reaction between the hydride and water, with concomitant H 2 evolution. This perspective highlights the most representative literature examples of MOFs as heterogeneous catalysts (or catalyst supports) for H 2 production from inorganic lightweight hydrides. Future trends in the field will also be discussed. (Figure Presented)

Chemical functionalization of carbon nanomaterials: Bridging the gap between simple carriers and smart (metalfree) catalysts

© 2017 Swiss Chemical Society. The last few years have witnessed a wonderful technological renaissance that boosted the development of carbon-based nanomaterials (CNMs) doped with light heteroelements and featuring hierarchical porous architectures as valuable metal-free catalysts for a number of key industrial transformations. To date, several approaches to their synthesis have been developed, although many of them lack any real control of the final doping and composition. In contrast, chemical functionalization offers a unique and powerful tool to tailor CNMs' chemical and electronic surface properties as a function of their downstream application in catalysis. Different catalytic processes (hydrolysis/esterification/transesterification reactions, C-C bond forming reactions, CO2 derivatization into products of added value and electrochemical oxygen reduction reactions (ORR)) can be conveniently promoted by these materials. In addition, selected examples from this series offer a valuable platform for the in-depth comprehension of the underlying reaction mechanisms. This perspective article offers an overview on the main examples of ad hoc chemically decorated CNMs successfully exploited as metal-free catalysts, highlighting at the same time the importance of the surface chemistry control for the design of more active, metal-free and single-phase heterogeneous catalysts

Misuse and Artifact in Factor Analytic Research

The theory of factor analysis has been developed for incorporating mathematical　statistical theories such as the maximum likelihood method and asymptotic methods. However, there have been several instances of misuse while employing procedures for factor analysis studies. In several studies, factor analysis has been performed by deleting items exhibiting the ceiling effect or floor effect. The number of samples required for factor analysis is not well known. Kaiser-Guttman criterion cannot be applied for determining the number of factors. Furthermore, various studies have employed Scree Graphs and Parallel Analysis for the said purpose, but no definitive method exists for the same. Orthogonal rotation methods such as Varimax cannot be considered as a conclusive solution. However, Geomin has been considered as a better rotation method not only for simple structure but also for more complex factor configuration. Simple structure and bifactor structure are discussed in connection to factor rotation problem. Although there are various artifacts associated with the usage of factor analysis, this issue can be addressed by verifying factorial invariance through multi-group simultaneous analysis incorporated by SEM programs such as Mplus and R Package.因子分析の理論は、最尤法と漸近的方法のような数理統計学的理論を組み込んだ形で発展してきた。しかしながら、因子分析研究の手順にはまだ誤用がみられる。いくつかの研究において、天井効果や床効果を示す項目を削除して因子分析が行われている。因子分析に必要なサンプル数は明確ではない。因子の数を決定するためにKaiser-Guttman 基準は使うことはできない。そして、この目的でScree Graph とParallel Analysis を使用している研究は数多くあるが、そのための決定的な方法はない。Varimax のような直交回転は最終的な解と考えることはできない。しかしながら、Geomin は単純構造だけでなくより複雑な因子の布置に対しても優れた回転方法と考えられている。因子回転問題を考慮した単純構造とbifactor 構造について議論した。因子分析の使い方には多くのartifacts があるが、この問題は、Mplus やR Package などのSEMプログラムによって組み込まれた複数集団の同時分析によって因子的不変性を検証することによって対処することができる

How to teach an old dog new (electrochemical) tricks: Aziridine-functionalized CNTs as efficient electrocatalysts for the selective CO<inf>2</inf> reduction to CO

© 2018 The Royal Society of Chemistry. The electrocatalytic conversion of CO2 to energy-rich chemicals or energy vectors is a highly challenging approach to cope with an ever increasing demand for energy storage and valorization of renewable resources. Herein we report on the electrocatalytic reduction of CO2 to CO using covalently N-decorated carbon nanotubes as highly efficient and chemoselective metal-free electrocatalysts. At odds with more conventional synthetic methods for the production of N-doped nanocarbons, chemical functionalization warrants a unique control of "surface N-defects" available for the process, ruling out any synergistic contribution to electrocatalysis coming from other surface or bulk N-containing groups. With a CO faradaic efficiency (FECO) close to 90% and productivity as high as 48 NLCO gN-1 h-1, NH-aziridine functionalized MWCNTs have shown CO2RR performance that is among the highest reported so far for related metal-free systems. At the same time, it has offered a unique view-point for the comprehension of the underlying structure-reactivity relationship

Novel yttrium and zirconium catalysts featuring reduced Ar-BIANH2 ligands for olefin hydroamination (Ar-BIANH2 = bis-arylaminoacenaphthylene)

The novel class of bis-arylaminoacenaphthylenes (Ar-BIANH(2)) was employed for the preparation of zirconium and yttrium complexes to be used as catalysts for cyclohydroamination of a number of primary and secondary aminoalkenes. The complex [(2,6-iPr(2)C(6)H(3)-BIAN)Zr(NMe2)(2)(eta(1)-NHMe2)] was isolated and completely characterized, including X-ray diffraction analysis. Despite its easy and almost quantitative isolation, it showed only moderate catalytic performance in the intramolecular hydroamination, irrespective of the cyclization precursor used. On the other hand, in situ generated Y-III complexes obtained using the same class of ligands were found to be very active, leading to the hydroamination of substrates including those normally reluctant in undergoing cyclization such as those featuring an internal non-activated C=C double bond. Electron donating substituents and especially steric hindrance on the ligand improve the performance of the catalysts, allowing us to decrease the catalyst loading to 1 mol% in the latter case

Lattice expansion of graphite oxide by pressure induced insertion of liquid ammonia

© 2015 Elsevier Ltd. All rights reserved. A pressure induced lattice expansion of Graphite Oxide (GO) in presence of NH3 was observed by X-ray diffraction during room temperature compression and decompression up to 7 GPa in a diamond anvil cell (DAC). A remarkable increase (∼11%) of the interlayer d-spacing of GO was observed between 0.2 and 1.1 GPa in the liquid phase of NH3, indicating the occurrence of molecular insertion between the GO layers. The expansion is reversible with the release of pressure, thus leading to a pressure induced breathing of the GO lattice. The presence of high density NH3 between the GO layers opens new perspectives for N-doping and chemical functionalization of GO and for designing new advanced carbon based nanostructured materials