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Adsorptive separation by porous solids provides an energy-efficient alternative for the purification of important chemical species compared to energy-intensive distillations. Particularly, the separation of linear hexane isomers from its branched counterparts is crucial to produce premium grade gasoline with high research octane number (RON). Herein, we report the synthesis of a new, flexible zinc-based metal-organic framework, [Zn5(μ3-OH)2(adtb)2(H2O)5·5 DMA] (Zn-adtb), constructed from a butterfly shaped carboxylate linker with underlying (4,8)-connected scu topology capable of separating the C6 isomers nHEX, 3MP, and 23DMB. The sorbate-sorbent interactions and separation mechanisms were investigated and analyzed through in situ FTIR, solid state NMR measurements and computational modeling. These studies reveal that Zn-adtb discriminates the nHEX/3MP isomer pair through a kinetic separation mechanism and the nHEX/23DMB isomer pair through a molecular sieving mechanism. Column breakthrough measurements further demonstrate the efficient separation of linear nHEX from the mono- and dibranched isomers.

Fluorosis has been regarded as a worldwide disease that seriously diminishes the quality of life through skeletal embrittlement and hepatic damage. Effective detection and removal of fluorinated chemical species such as fluoride ions (F-) and perfluorooctanoic acid (PFOA) from drinking water are of great importance for the sake of human health. Aiming to develop water-stable, highly selective and sensitive fluorine sensors, we have designed a new luminescent MOF In(tcpp) using a chromophore ligand 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine (H4tcpp). In(tcpp) exhibits high sensitivity and selectivity for turn-on detection of F- and turn-off detection of PFOA with a detection limit of 1.3 μg L-1 and 19 μg L-1, respectively. In(tcpp) also shows high recyclability and can be reused multiple times for F- detection. The mechanisms of interaction between In(tcpp) and the analytes are investigated by several experiments and DFT calculations. These studies reveal insightful information concerning the nature of F- and PFOA binding within the MOF structure. In addition, In(tcpp) also acts as an efficient adsorbent for the removal of F- (36.7 mg g-1) and PFOA (980.0 mg g-1). It is the first material that is not only capable of switchable sensing of F- and PFOA but also competent for removing the pollutants via different functional groups.

The potential implementation of extreme ultraviolet (EUV) lithography into next generation device processing is bringing urgency to identify resist materials that optimize EUV lithographic performance. Inorganic/organic hybrid nanoparticles or clusters constitute a promising new class of materials, with high EUV sensitivity from the core and tunable chemistry through the coordinating ligands. Development of a thorough mechanistic understanding of the solubility switching reactions in these materials is an essential first step toward their implementation in patterning applications but remains challenging due to the complexity of their structures, limitations in EUV sources, and lack of rigorous in situ characterization. Here, we report a mechanistic investigation of the solubility switching reactions in hybrid clusters comprising a small HfOx core capped with a methacrylic acid ligand shell (HfMAA). We show that EUV-induced reactions can be studied by performing in situ infrared (IR) spectroscopy of electron-irradiated films using a variable energy electron gun. Combining additional ex situ metrology, we track the chemical evolution of the material at each stage of a typical resist processing sequence. For instance, we find that a cross-linking reaction initiated by decarboxylation of the methacrylate ligands under electron irradiation constitutes the main solubility switching mechanism, although there are also chemical changes imparted by a typical post application bake (PAB) step alone. Lastly, synchrotron-based IR microspectroscopy measurements of EUV-irradiated HfMAA films enable a comparison of reactions induced by EUV vs electron beam irradiation of the same resist material, yielding important insight into the use of electron beam irradiation as an experimental model for EUV exposure.

Anatase/rutile constituting TiO2 thin films were prepared by sputter deposition, and the influence of the post-annealing step with a narrow window at 200 °C revealed a gaining factor of 5 in H2 production. An in-depth analysis of the photocatalytic performance revealed the dominant role of intermediate states rather than the heterocrystalline nature and the mesoscale structure. Structural, chemical and optical investigations based on scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible spectroscopy and photoluminescence supported by ab initio calculation correlated the H2 production with the dual presence of OH− and Ti3+ defects in the form of titanium interstitial atoms. In addition, steady-state photoluminescence measurements determined the chemically active role of ethanol, commonly used as a hole scavenger, in inducing deep hole traps upon dissociation on the surface. These results give new directions for the design of TiO2 based photocatalytic systems for light-driven H2 production through water splitting, guided by a detailed description of defects present on the electronic structure and their chemical identification. [ABSTRACT FROM AUTHOR]

We perform first-principles calculations to explore the electronic, thermodynamic and dielectric properties of two-dimensional (2D) layered, alkaline-earth hydroxides Ca(OH) 2 and Mg(OH) 2 . We calculate the lattice parameters, exfoliation energies and phonon spectra of monolayers and also investigate the thermal properties of these monolayers, such as the Helmholtz free energy, heat capacity at constant volume and entropy as a function of temperature. We employ Density Functional Perturbation Theory (DFPT) to calculate the in-plane and out-of-plane static dielectric constant of the bulk and monolayer samples. We compute the bandgap and electron affinity values using the HSE06 functional and estimate the leakage current density of transistors with monolayer Ca(OH) 2 and Mg(OH) 2 as dielectrics when combined with HfS 2 and WS 2 , respectively. Our results show that bilayer Mg(OH) 2 (EOT∼0.60 nm) with a lower solubility in water offers higher out-of-plane dielectric constants and lower leakage currents than does bilayer Ca(OH) 2 (EOT∼0.56 nm). Additionally, the out-of-plane dielectric constant, leakage current and EOT of Mg(OH) 2 outperform bilayer h-BN. We verify the applicability of Anderson's rule and conclude that bilayers of Ca(OH) 2 and Mg(OH) 2 , respectively, paired with lattice-matched monolayer HfS 2 and WS 2 , are effective structural combinations that could lead to the development of innovative multi-functional Field Effect Transistors (FETs). [ABSTRACT FROM AUTHOR]

Anatase/rutile constituting TiO 2 thin films were prepared by sputter deposition, and the influence of the post-annealing step with a narrow window at 200 °C revealed a gaining factor of 5 in H 2 production. An in-depth analysis of the photocatalytic performance revealed the dominant role of intermediate states rather than the heterocrystalline nature and the mesoscale structure. Structural, chemical and optical investigations based on scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible spectroscopy and photoluminescence supported by ab initio calculation correlated the H 2 production with the dual presence of OH - and Ti 3+ defects in the form of titanium interstitial atoms. In addition, steady-state photoluminescence measurements determined the chemically active role of ethanol, commonly used as a hole scavenger, in inducing deep hole traps upon dissociation on the surface. These results give new directions for the design of TiO 2 based photocatalytic systems for light-driven H 2 production through water splitting, guided by a detailed description of defects present on the electronic structure and their chemical identification.

Pyrazine-linked hybrid ultramicroporous (pore size <7 Å) materials (HUMs) offer benchmark performance for trace carbon capture thanks to strong selectivity for CO 2 over small gas molecules, including light hydrocarbons. That the prototypal pyrazine-linked HUMs are amenable to crystal engineering has enabled second generation HUMs to supersede the performance of the parent HUM, SIFSIX-3-Zn, mainly through substitution of the metal and/or the inorganic pillar. Herein, we report that two isostructural aminopyrazine-linked HUMs, MFSIX-17-Ni (17=aminopyrazine; M=Si, Ti), which we had anticipated would offer even stronger affinity for CO 2 than their pyrazine analogs, unexpectedly exhibit reduced CO 2 affinity but enhanced C 2 H 2 affinity. MFSIX-17-Ni are consequently the first physisorbents that enable single-step production of polymer-grade ethylene (>99.95 % for SIFSIX-17-Ni) from a ternary equimolar mixture of ethylene, acetylene and CO 2 thanks to coadsorption of the latter two gases. We attribute this performance to the very different binding sites in MFSIX-17-Ni versus SIFSIX-3-Zn., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)