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.

中文翻译：

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孔雀石中镁替代铜：合成和结构效应的见解

碱式碳酸铜孔雀石的相宽，Cu ₂ CO ₃ (OH) ₂，在用镁替代后进行了详细研究。在先前对无定形前体的研究的扩展中，水热老化步骤的引入允许回收具有高达 37 原子％ Mg（金属含量）的结晶羟基碳酸盐样品，这些样品适合作为用于 CO 加氢的 Cu / MgO 催化剂的前体。同时改进 X 射线粉末衍射和对分布函数 (PDF) 数据以及互补的光谱洞察力（X 射线吸收和红外光谱）表明，镁含量高达 18 原子％的样品是相纯镁孔雀石，但镁当 mcguinnessite (CuMgCO ₃ (OH) ₂) 被接受为副相。在一项补充研究中，发现在老化过程中镁含量不断增加，并通过 PDF 研究了相应的结构演变。这些发现增加了对结晶 Cu、Mg 羟基碳酸盐的老化化学的重要认识。_{此外，通过热重分析、X 射线粉末衍射和 N 2}物理吸附对 Mg 含量高达 37% 的纯镁孔雀石和含麦晶石的样品进行了检测，发现它们是用作制备前体的有前途的候选者Cu/MgO 催化剂。