Department of Chemistry, Central College, Bangalore University, Bangalore 560 001, India.
Inorg Chem. 2010 Dec 20;49(24):11370-7. doi: 10.1021/ic101177d. Epub 2010 Nov 15.
Incorporation of Zn(2+) into bayerite results in the formation of a cation-ordered layered double hydroxide (LDH) of monoclinic symmetry in which about half the vacancies of Al(OH)(3) are occupied by Zn(2+) giving rise to positively charged layers. Charge compensation takes place by the incorporation of sulfate ions in the interlayer region. Structure refinement reveals that the adjacent layers in the crystal are related by a 2(1) axis (we call it 2M(1) polytype) with sulfate coordinating in the D(2d) symmetry in the interlayer region. Another polytype in which adjacent layers are related by a 2-fold axis (2M(2) polytype) can also be envisaged. Faulted crystals arising from intergrowths of the 2M(2) polytype within the 2M(1) structure were also obtained. These bayerite-based LDHs have a distinctly different interlayer chemistry when compared to the better known brucite-based LDHs, in that they have a strong affinity for tetrahedral ions such as SO(4)(2-), CrO(4)(2-), and MoO(4)(2-) and a poor affinity for CO(3)(2-) ions. These observations have implications for the use of LDHs in applications related to chromate sorption.
锌（Ⅱ）掺入水铝氧石会导致形成具有单斜对称的阳离子有序层状双氢氧化物（LDH），其中约一半的铝（OH）（3）空位被锌（Ⅱ）占据，从而产生带正电荷的层。通过在层间区域掺入硫酸根离子来实现电荷补偿。结构精修表明，晶体中相邻的层通过 2（1）轴相关（我们称之为 2M（1）多型），在层间区域中，硫酸根以 D（2d）对称性配位。也可以设想相邻层通过 2 重轴相关的另一种多型（2M（2）多型）。还获得了由 2M（2）多型在 2M（1）结构内的混晶产生的位错晶体。与更为人熟知的水镁石基 LDH 相比，这些基于水铝氧石的 LDH 的层间化学性质明显不同，因为它们对四面体离子（如 SO（4）（2-）、CrO（4）（2-）和 MoO（4）（2-）具有很强的亲和力，而对 CO（3）（2-）离子的亲和力较弱。这些观察结果对 LDH 在与铬酸盐吸附相关的应用中具有重要意义。
