Selective sorption of oxygen and nitrous oxide by an electron donor-incorporated flexible coordination network

Incorporating strong electron donor functionality into flexible coordination networks is intriguing for sorption applications due to a built-in mechanism for electron-withdrawing guests. Here we report a 2D flexible porous coordination network, [Ni₂(4, 4′-bipyridine)(VTTF)₂]n(1) (where H₂VTTF = 2, 2′-[1, 2-bis(4-benzoic acid)-1, 2ethanediylidene]bis-1, 3-benzodithiole), which exhibits large structural deformation from the as-synthesized or open phase (1α) into the closed phase (1β) after guest removal, as demonstrated by X-ray and electron diffraction. Interestingly, upon exposure to electron-withdrawing species, 1β reversibly undergoes guest accommodation transitions; 1α⊃O₂ (90 K) and 1α⊃N₂O (185 K). Moreover, the 1β phase showed exclusive O₂ sorption over other gases (N₂, Ar, and CO) at 120 K. The phase transformations between the 1α and 1β phases under these gases were carefully investigated by in-situ X-ray diffraction, in-situ spectroscopic studies, and DFT calculations, validating that the unusual sorption was attributed to the combination of flexible frameworks and VTTF (electron-donor) that induces strong interactions with electron-withdrawing species

Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material

Structural changes at the active site of an enzyme induced by binding to a substrate molecule can result in enhanced activity in biological systems. Herein, we report that the new hybrid ultramicroporous material sql-SIFSIX-bpe-Zn exhibits an induced fit binding mechanism when exposed to acetylene, C₂H₂. The resulting phase change affords exceptionally strong C₂H₂ binding that in turn enables highly selective C₂H₂/C₂H₄ and C₂H₂/CO₂ separation demonstrated by dynamic breakthrough experiments. sql-SIFSIX-bpe-Zn was observed to exhibit at least four phases: as-synthesised (α); activated (β); and C₂H₂ induced phases (β' and γ). sql-SIFSIX-bpe-Zn-β exhibited strong affinity for C₂H₂ at ambient conditions as demonstrated by benchmark isosteric heat of adsorption (Qst ) of 67.5 kJ mol⁻¹ validated through in situ pressure gradient differential scanning calorimetry (PG-DSC). Further, in situ characterisation and DFT calculations provide insight into the mechanism of the C₂H₂ induced fit transformation, binding positions and the nature of host-guest and guest-guest interactions

Nanoconfinement of High Hydrogen-to-Metal Ratio Lanthanum Hydrides in Functionalized Carbon Hosts

Metal hydrides with a high hydrogen content are important for materials-based hydrogen storage and high-temperature superconductivity. Nanoconfinement of metal hydrides in porous hosts is a promising strategy to tune the thermodynamic stability and control the hydrogen-to-metal ratio. However, lanthanum hydride (LaHx) nanoconfinement in porous materials has been limited due to the challenges associated with isolating and stabilizing nanoparticles of La or La-hydrides. Here we successfully demonstrated the chemical reduction of La(III) salts to La(0), and subsequent infiltration into pure CMK-3 and nitrogen-doped CMK-3 (NCMK-3) porous carbons. Transmission electron microscopy measurements revealed a uniform distribution of LaHx species within the carbon hosts, while X-ray absorption and photoelectron spectroscopy provided detailed information about the local chemical environment. Sieverts measurements indicate that LaHx@NCMK-3 could desorb up to 0.75 wt % hydrogen, which is higher than non-nitrogen-functionalized CMK-3 (0.43 wt % H). Density Functional Theory and ab initio molecular dynamics calculations indicate that host-guest interaction energies are favorable for porous carbon with nitrogen defects, which is supported by experimental evidence. Moreover, high-pressure synchrotron X-ray diffraction measurements were conducted using a diamond anvil cell up to 60 GPa and reveal that the nitrogen-functionalized nanoporous carbon host favors the formation of higher H:La ratios in the presence of ammonia borane compared to the pure CMK-3 host. This approach could serve as a suitable platform for developing nanoscale superconducting materials at lower pressures and temperatures compared to bulk

Crystal engineering of flexible metal organic materials

Crystal engineering is the field of chemistry that studies the design, properties, and application of crystals. An aspect of crystal engineering is the design of coordination networks formed by the rational combination of metal nodes and organic linker ligands. Porous coordination networks, which are also known as porous coordination polymers (PCPs), Metal Organic Materials (MOMs) or Metal Organic Frameworks (MOFs), have captured the interest of researchers worldwide because of their inherent modularity and amenability to crystal engineering principles. PCPs and porous MOMs have been classified into four generations: 1st generation materials collapse on guest removal and lose crystallinity; 2nd generation materials possess a rigid nature upon guest insertion/removal and exhibit a type I isotherm; 3rd generation materials alter their original structure and maintain overall framework connectivity when exposed to external stimuli such as guest incorporation/removal, pressure and heat; 4th generation materials can be fine-tuned via post synthetic modification (PSM), defects or solid solutions. 3 rd generation materials or porous flexible MOMs, have attracted attention owing to  their potential applications in gas storage, separation, drug delivery and catalysis. These flexible MOMs tend to exhibit ‘stepped’ or ‘S-shaped’ isotherm profiles. Herein, we propose classification of such MOMs based on their gas sorption isotherm profiles as follows, i) type F-I (gradual change from open to more open, ii) type F-II (sudden change from open to more open sudden), iii) type F-III (gradual change from closed to open gradual), iv) type F-IV(sudden change from closed to open) and v) type F-V (shape-memory effect). This thesis also examines the three types of network topologies, primitive cubic unit (pcu), diamondiod (dia) and square lattice (sql) networks. The systematic studies we conducted herein offer design principles for future studies of porous flexible coordination networks in terms of understanding their structural transformations and improving the performance of gas storage/separation.  </p

Solvent-Dependent Delamination, Restacking, and Ferroelectric Behavior in a New Charge-Separated Layered Compound: NH4] Ag-3(C9H5NO4S)(2)(C13H14N2)(2)]center dot 8H(2)O

A new anionic coordination polymer, NH4] Ag-3( C9H5NO4S)(2)( C13H14N2)(2)]center dot 8H(2)O, with a two-dimensional structure, has been synthesized by a reaction between silver nitrate, 8-hydroxyquinoline-5-sulfonic acid (HQS), and 4,4'-tri-methylene dipyridine (TMDP). The compound stabilizes in a noncentrosymmetric space group, and the lattice water molecules and the charge-compensating NH4](+) group occupy the inter-lamellar spaces. The lattice water molecules can be fully removed and reinserted, which is accompanied by a crystalline-amorphous-crystalline transformation. This transformation resembles the collapse/delamination and restacking of the layers. To the best of our knowledge, this is the first observation of delamination and restacking in an inorganic coordination polymer that contains silver. The presence of a natural dipole (the anionic framework and cationic ammonium ions) along with the noncentrosymmetric space group gives rise to the room-temperature ferroelectric behavior of the compound. The ferroelectric behavior is also water-dependent and exhibits a ferroelectric-paraelectric transformation. The temperature-dependent dielectric measurements indicate that the ferroelectric/paraelectric transformation occurs at 320 K. This transformation has also been investigated by using in-situ IR spectroscopy and PXRD studies. The second-harmonic generation (SHG) study indicated values that are comparable to some of the known SHG solids, such as potassium dihydrogen phosphate (KDP) and urea

Control of local flexibility towards <i>p</i>-xylene sieving in Hofmann-type porous coordination polymers

Tuning of local flexibility towards p-xylene achieved by the control of the specific combination of coordination metal centers in Hofmann-type porous coordination polymers.</p

Microwave assisted hydrothermal synthesis of Ag2O/α-Bi2O3 heterostructures with highly enhanced photocatalysis and their environmental interest

A methodological analysis is made in the rational synthesis of the Ag2O/α-Bi2O3, p-n junction heterostructure with significant application, possessing substantial electron-hole recombination acting as solar catalysts through powerful and modest microwave inspired hydrothermal technique. Meanwhile, Ag2O/α-Bi2O3 is intermediary for single step Methyl Red (MR) dye photocatalytic degradation. Additionally, the experimental and characterization findings demonstrated that sunlight-induced surface effects on synthetic materials remove heavy metals such as Lead (Pb) sunder solar irradiation. The research work provides a strategy for excellent and efficient design of photocatalyst as an eco-friendly and biomedical approach. Electrochemical studies, such as photocurrent calculations, band positions and EIS for Ag2O/α-Bi2O3 heterostructures were also carried out. The study helps to broaden the search for and development of new hybrid composites for electrochemical applications and environmental interest

Fabrication of spherical porous pAg(2)O-nWO(3)/Ag/GNS heterostructure with enhanced photocatalytic activity through plasmonic S-scheme mechanism and its complementing biological interest

The synthesis and characterization of Ag2OWO3/Ag/GNS heterostructure with desired modifications has been elucidated in the contemporary study. The fabrication involves a simple hydrothermal method for the configuration of fascinating heterostructures intended to photo-catalytically degrade Eosin Yellow (EY) dye. The toxic dye molecules were converted into non-toxic molecular intermediates, also the elimination of heavy metals from industrial wastewater, being trapped in the pores of heterostructure. The pn junction photocatalyst with plasmonic resonance of Ag for abolition of electron and hole coupling, enhances the photo-response where the catalyst abides S-Scheme mechanism. The work functions of active photocatalysts as calculated for Ag2O is 6.61eV and WO3 is 6.04eV. Furthermore, the Ag2OWO3/Ag/GNS photocatalysts recovery and reuse in several trials without any noticeable loss of photocatalytic activity, complimented the recyclability of the heterostructure. To ensure the safety of the environment on heterostructure being released, toxicity analysis were carried out. These Ag2OWO3/Ag/GNS heterostructures had optimistic result on cytotoxicity assay, and on Musmusculus skin melanoma cells (B16-F10), with anti-microbial/fungal properties. Thereby, the contemporary experiment upholds efficient photocatalysis and ropes multiple errands on biological applications