Substitution of Copper by Magnesium in Malachite: Insights into the Synthesis and Structural Effects.

The phase width of the copper hydroxycarbonate malachite, Cu2CO3(OH)2, upon substitution with magnesium has been studied in detail. In extension of a previous study on amorphous precursors, the introduction of a hydrothermal aging step allowed the retrieval of crystalline hydroxycarbonate samples with up to 37 atom % Mg (metal content) that are suitable candidates as precursors to Cu/MgO catalysts for CO hydrogenation. Simultaneous refinements of X-ray powder diffraction and pair distribution function (PDF) data as well as complementary spectroscopic insight (X-ray absorption and infrared spectroscopy) revealed that samples with up to 18 atom % Mg are phase-pure magnesian malachites but the magnesium content can be increased beyond this threshold when mcguinnessite (CuMgCO3(OH)2) is accepted as a side phase. In a complementary study, a continuous increase of the magnesium fraction was found during aging and the corresponding structural evolution was studied by means of PDF. These findings add significant insight into the aging chemistry of crystalline Cu,Mg hydroxycarbonates. Furthermore, both phase-pure magnesian malachite and mcguinnessite-containing samples with up to 37 atom % Mg have been examined by thermogravimetry, X-ray powder diffraction, and N2 physisorption and were found to be promising candidates for use as precursors for the preparation of Cu/MgO catalysts.

Ionothermal syntheses of nano- and microstructured ternary copper-indium-chalcogenides.

Ternary compounds of copper indium selenide nano- and microsized materials were prepared through colloidal synthesis using an indium(III) selenide precursor and copper(I) chloride via a microwave-assisted ionothermal route. The indium(III) selenide precursor used in the reaction was formed in situ from a diphenyl diselenide precursor and chloroindate(III) ionic liquids (ILs), also via a microwave-assisted ionothermal route. The crystal structures of three intermediates, namely, CuCl2(OMe)2(H2O)){Cu(PhSeO2)2}n, [CuCl(Se2Ph2)2]n, and [C8mim]3{Cu(I)Cl2Cu(II)OCl8}n, were determined after formation through a ionothermal procedure utilizing metal-containing imidazolium ILs and a selenium precursor with conventional heating. Herein, we compare the use of microwave irradiation over conventional heating with different ILs on the stoichiometry of the resulting products. The influence of the reaction temperature, reaction time, order of addition of reagents, and variation of ILs, which were characterized using PXRD, SEM, and EDX, on the final products was investigated.