A layered chlorophosphate, Na-3[Cd4Cl3(HPO4)(2)(H2PO4)(4)], containing Na+ ions in the interlamellar space

Reaction between CdCl2.H2O and NaH2PO4.H2O Under hydrothermal conditions gives rise to a new cadmium chlorophosphate of the formula Na-3[Cd4Cl3(HPO4)(2)(H2PO4)(4)] I. This material crystallizes in the orthorhombic system with space group Fmm2(no. 42). I has macroanionic layers of [Cd4Cl3(HPO4)(2)(H2PO4)(4)](3-) with Na+ ions in the interlamellar space. The discovery of such compounds suggests that metathetic reactions carried out under hydrothermal conditions may provide a novel route for the synthesis of new open-framework structures

Preferential Adsorption of CO₂ in an Ultramicroporous MOF with Cavities Lined by Basic Groups and Open-Metal Sites

Here, we present a new ultramicroporous Cu₂ paddlewheel based MOF. This ultramicroporous MOF has most of the features such as porosity (BET surface area = 945 m²/g), CO₂ capacity (3.5 mmol/g at ambient temperature and pressure), CO₂/N₂ selectivity (sCO₂/N₂ = 250), and fast CO₂ diffusion kinetics (<i>D</i>_c = 2.25 × 10^–9 m²/s), comparable to some of the other high-performing ultramicroporous MOFs, with strong binding sites. Typically, such MOFs exhibit strong CO₂–framework interactions (evidenced from a heat of adsorption ≥ 38 kJ/mol). However, the MOF explained here, despite having channels lined by the amine and the open-metal sites, possesses only a moderate CO₂–framework interaction (HOA = 26 kJ/mol). Using periodic DFT, we have probed this counterintuitive observation

Facile proton conduction via ordered water molecules in a phosphonate metal-organic framework

A new phosphonate metal-organic framework (MOF) with a layered motif but not that of the classical hybrid inorganic-organic solid is presented. Zn3(L)(H2O)2 \ub72H2O (L ) [1,3,5-benzenetriphosphonate]6-), henceforth denoted as PCMOF-3, contains a polar interlayer lined with Zn-ligated water molecules and phosphonate oxygen atoms. These groups serve to anchor free water molecules into ordered chains, as observed by X-ray crystallography. The potential for proton conduction via the well-defined interlayer was studied by 2H solid-state NMR spectroscopy and AC impedance spectroscopy. The proton conductivity in H2 was measured as 3.5 7 10-5 S cm-1 at 25 \ub0C and 98% relative humidity. More interestingly, an Arrhenius plot gave a low activation energy of 0.17 eV for proton transfer, corroborating the solid-state NMR data that showed exchange between all deuterium sites in the D2O analogue of PCMOF-3, even at -20 \ub0C.Peer reviewed: YesNRC publication: Ye

Enhancing Water Stability of Metal–Organic Frameworks via Phosphonate Monoester Linkers

A new porous metal–organic framework (MOF), barium tetraethyl-1,3,6,8-pyrenetetraphosphonate (CALF-25), which contains a new phosphonate monoester ligand, was synthesized through a hydrothermal method. The MOF is a three-dimensional structure containing 4.6 Å × 3.9 Å rectangular one-dimensional pores lined with the ethyl ester groups from the ligand. The presence of the ethyl ester groups makes the pores hydrophobic in nature, as determined by the low heats of adsorption of CH₄, CO₂, and H₂O (14.5, 23.9, and 45 kJ mol^–1, respectively) despite the polar and acidic barium phosphonate ester backbone. The ethyl ester groups within the pores also protect CALF-25 from decomposition by water vapor, with crystallinity and porosity being retained after exposure to harsh humid conditions (90% relative humidity at 353 K). The use of phosphonate esters as linkers for the construction of MOFs provides a method to protect hydrolytically susceptible coordination backbones through kinetic blocking

'Insecta exotica'

A new porous metal–organic framework (MOF), barium tetraethyl-1,3,6,8-pyrenetetraphosphonate (CALF-25), which contains a new phosphonate monoester ligand, was synthesized through a hydrothermal method. The MOF is a three-dimensional structure containing 4.6 Å × 3.9 Å rectangular one-dimensional pores lined with the ethyl ester groups from the ligand. The presence of the ethyl ester groups makes the pores hydrophobic in nature, as determined by the low heats of adsorption of CH₄, CO₂, and H₂O (14.5, 23.9, and 45 kJ mol^–1, respectively) despite the polar and acidic barium phosphonate ester backbone. The ethyl ester groups within the pores also protect CALF-25 from decomposition by water vapor, with crystallinity and porosity being retained after exposure to harsh humid conditions (90% relative humidity at 353 K). The use of phosphonate esters as linkers for the construction of MOFs provides a method to protect hydrolytically susceptible coordination backbones through kinetic blocking

Bulky Isopropyl Group Loaded Tetraaryl Pyrene Based Azo-Linked Covalent Organic Polymer for Nitroaromatics Sensing and CO₂ Adsorption

An azo-linked covalent organic polymer, Py-azo-COP, was synthesized by employing a highly blue-fluorescent pyrene derivative that is multiply substituted with bulky isopropyl groups. Py-azo-COP was investigated for its sensing and gas adsorption properties. Py-azo-COP shows selective sensing toward the electron-deficient polynitroaromatic compound picric acid among the many other competing analogs that were investigated. Apart from its chemosensing ability, Py-azo-COP (surface area 700 m² g^–1) exhibits moderate selectivity toward adsorption of CO₂ and stores up to 8.5 wt % of CO₂ at 1 bar and 18.2 wt % at 15.5 bar at 273 K, although this is limited due to the electron-rich −NN– linkages being flanked by isopropyl groups. Furthermore, the presence of a large number of isopropyl groups imparts hydrophobicity to Py-azo-COP, as confirmed by the increased adsorption of toluene compared to that of water in the pores of the COP