De Bellis Jacopo, Ochoa-Hernández Cristina, Farès Christophe, Petersen Hilke, Ternieden Jan, Weidenthaler Claudia, Amrute Amol P, Schüth Ferdi
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.
J Am Chem Soc. 2022 Jun 1;144(21):9421-9433. doi: 10.1021/jacs.2c02181. Epub 2022 May 23.
Aluminum oxides, oxyhydroxides, and hydroxides are important in different fields of application due to their many attractive properties. However, among these materials, tohdite (5AlO·HO) is probably the least known because of the harsh conditions required for its synthesis. Herein, we report a straightforward methodology to synthesize tohdite nanopowders (particle diameter ∼13 nm, specific surface area ∼102 m g) via the mechanochemically induced dehydration of boehmite (γ-AlOOH). High tohdite content (about 80%) is achieved upon mild ball milling (400 rpm for 48 h in a planetary ball mill) without process control agents. The addition of AlF can promote the crystallization of tohdite by preventing the formation of the most stable α-AlO, resulting in the formation of almost phase-pure tohdite. The availability of easily accessible tohdite samples allowed comprehensive characterization by powder X-ray diffraction, total scattering analysis, solid-state NMR (H and Al), N-sorption, electron microscopy, and simultaneous thermal analysis (TG-DSC). Thermal stability evaluation of the samples combined with structural characterization evidenced a low-temperature transformation sequence: 5AlO·HO → κ-AlO → α-AlO. Surface characterization via DRIFTS, ATR-FTIR, D/H exchange experiments, pyridine-FTIR, and NH-TPD provided further insights into the material properties.
氧化铝、羟基氧化物和氢氧化物因其众多吸引人的特性而在不同应用领域中具有重要地位。然而，在这些材料中，水软铝石（5AlO·H₂O）可能是最鲜为人知的，因为其合成需要苛刻的条件。在此，我们报道了一种直接的方法，通过对勃姆石（γ -AlOOH）进行机械化学诱导脱水来合成水软铝石纳米粉末（粒径约13 nm，比表面积约102 m²/g）。在不使用过程控制剂的情况下，通过温和球磨（在行星式球磨机中以400 rpm转速球磨48小时）可获得高含量（约80%）的水软铝石。添加AlF₃可通过防止最稳定的α -Al₂O₃形成来促进水软铝石的结晶，从而形成几乎纯相的水软铝石。易于获取的水软铝石样品使得能够通过粉末X射线衍射、全散射分析、固态NMR（¹H和²⁷Al）、N₂吸附、电子显微镜以及同步热分析（TG - DSC）进行全面表征。结合结构表征对样品进行的热稳定性评估证明了其低温转变序列：5AlO·H₂O → κ -Al₂O₃ → α -Al₂O₃。通过漫反射红外傅里叶变换光谱（DRIFTS）、衰减全反射傅里叶变换红外光谱（ATR - FTIR）、D/H交换实验、吡啶 - FTIR和NH₃ - 程序升温脱附（NH₃ - TPD）进行的表面表征进一步深入了解了材料特性。
