A Highly Stable Yttrium Organic Framework as a Host for Optical Thermometry and D2 O Detection

The yttrium organic framework (Y0.89 Tb0.10 Eu0.01 )6 (BDC)7 (OH)4 (H2 O)4 (BDC=benzene-1,4-dicarboxylate) is hydrothermally stable up to at least 513 K and thermally stable in air in excess of 673 K. The relative intensities of luminescence of Tb3+ and Eu3+ are governed by Tb3+ -to-Eu3+ phonon-assisted energy transfer and Tb3+ -to-ligand back transfer and are responsible for the differing temperature-dependent luminescence of the two ions. This provides a ratiometric luminescent thermometer in the 288-573 K temperature range, not previously seen for MOF materials, with a high sensitivity, 1.69±0.04 % K-1 at 523 K. In aqueous conditions, loosely bound H2 O can be replaced by D2 O in the same material, which modifies decay lifetimes to yield a quantitative luminescent D2 O sensor with a useful sensitivity for practical application.

Tracking the dissolution-recrystallization structural transformation (DRST) of copper(II) complexes: a combined crystallographic, mass spectrometric and DFT study

Methanol- and temperature-induced dissolution-recrystallization structural transformation (DRST) was observed among two novel Cu^II complexes. This is first time that the combination of X-ray crystallography, mass spectrometry and density functional theory (DFT) theoretical calculations has been used to describe the fragmentation and recombination of a mononuclear Cu^II complex at 60 °C in methanol to obtain a binuclear copper(II) complex. Combining time-dependent high-resolution electrospray mass spectrometry, we propose a possible mechanism for the conversion of bis(8-methoxyquinoline-κ²N,O)bis(thiocyanato-κN)copper(II), [Cu(NCS)₂(C₁₀H₉NO)₂], Cu1, to di-μ-methanolato-κ⁴O:O-bis[(8-methoxyquinoline-κ²N,O)(thiocyanato-κN)copper(II)], [Cu₂(CH₃O)₂(NCS)₂(C₁₀H₉NO)₂], Cu2, viz. [Cu(SCN)₂(L)₂] (Cu1) → [Cu(L)₂] → [Cu(L)]/L → [Cu₂(CH₃O)₂(NCS)₂(L)₂] (Cu2). We screened the antitumour activities of L (8-methoxyquinoline), Cu1 and Cu2 and found that the antiproliferative effect of Cu2 on some tumour cells was much greater than that of L and Cu1.

A hydrothermally stable ytterbium metal-organic framework as a bifunctional solid-acid catalyst for glucose conversion

Yb6(BDC)7(OH)4(H2O)4 contains both bridging hydroxyls and metal-coordinated waters, possessing Brønsted and Lewis acid sites. The material crystallises from water at 200 °C. Using the solid as a heterogenous catalyst, glucose is converted into 5-hydroxymethylfurfural, via fructose, with a total selectivity of ∼70% after 24 hours at 140 °C in water alone: the material is recyclable with no loss of crystallinity.

A kinetic and mechanistic study into the transformation of calcium sulfate hemihydrate to dihydrate

The conversion of CaSO4·0.5H2O to CaSO4·2H2O is of great importance industrially, being the reaction behind plasterboard production and the setting of medical plasters. A detailed kinetic and mechanistic study of this process was conducted using time-resolved synchrotron X-ray diffraction in this work. The CaSO4·2H2O product is very similar regardless of whether the α- or β-form of CaSO4·0.5H2O is used as the starting material, but the reaction process is very different. The induction time is usually shorter for α-CaSO4·0.5H2O than β-CaSO4·0.5H2O, and a greater conversion percentage is observed with the former (although in neither case does the reaction proceed to 100% completion). The temperature of the system, widely used in industry as an indirect measure of the extent of the hydration process, is found to be a poor proxy for this, with the maximum temperature reached well before the reaction is complete. The Avrami-Erofe'ev and Gualtieri models could both be fitted to the experimental data, with the fits being substantially closer in the case of α-CaSO4·0.5H2O. The rate of reaction in the Avrami model tends to increase with the amount of gypsum seeds added to accelerate the process, and the importance of nucleation declines. The Gualtieri analysis suggested that the rate of nucleation increases substantially with the amount of seeds added, while there are less distinct changes in the rate of crystal growth. At low seed concentrations (<0.5% w/w) the rate of crystal growth is greater than the rate of nucleation, but at concentrations above 0.5% w/w nucleation is faster. These findings represent the first synchrotron study of the conversion of CaSO4·0.5H2O to CaSO4·2H2O, and will be of importance to gypsum producers globally.

Four new metal–organic frameworks based on diverse secondary building units: sensing and magnetic properties

Four new metal–organic frameworks based on diverse secondary building units were assembled and 1 showed high selectivity in the detection of CrO₄²⁻, Cr₂O₇²⁻, MnO₄⁻ and Fe³⁺.