Ligand-assisted liquid crystal templating in mesoporous niobium oxide molecular sieves
Ligand-assisted liquid crystal templating in mesoporous niobium oxide molecular sieves
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DOI：
10.1021/ic951533p
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发表时间：
1996-05-22
影响因子：
4.6
通讯作者：
Ying, JY
中科院分区：
文献类型：
--
作者：
Antonelli, DM;Nakahira, A;Ying, JY
系统研究了 Nb-TMS1（一种铌基介孔六方堆积过渡金属氧化物分子筛）的形成因素。这种材料的合成是通过一种新颖的配体辅助液晶模板机制实现的，其中使用离散的共价键来指导有机相和无机相之间的模板相互作用。一般来说，Nb-TMS1 的合成受起始条件（如温度、表面活性剂与金属的比例、pH 值和溶剂）的影响比初始水解步骤后的温度和老化时间的影响更大。结果还表明，Nb-TMS1 可以在强烈不利于胶束形成的条件下合成。这表明 Nb-TMS1 是通过自组装和伴随冷凝的机制形成的。研究发现，随着表面活性剂与金属比例的增加，可以形成新的六方P63/mmc（Nb-TMS2）和层状（Nb-TMS4）相，而增加表面活性剂链长则形成新的立方相（Nb-TMS3）。尺寸高达数毫米的 Nb-TMS1 晶体也已生长。这些晶体比报道的最大介孔晶体大 3 个数量级。这些晶体在通过酸处理去除胶束后仍保留其结构，因此作为量子线的主体非常受关注。
A systematic study of the factors governing the formation of Nb-TMS1, a niobium-based mesoporous hexagonally-packed transition metal oxide molecular sieve, is reported. The synthesis of this material was achieved through a novel ligand-assisted liquid crystal templating mechanism in which a discrete covalent bond is used to direct the templating interaction between the organic and inorganic phases. In general, the synthesis of Nb-TMS1 is more strongly affected by starting conditions such as temperature, surfactant-to-metal ratio, pH, and solvent than by temperature and time of aging after the initial hydrolysis step. The results also show that Nb-TMS1 can be synthesized under conditions which strongly disfavor the formation of micelles. This suggests that Nb-TMS1 is formed via a mechanism involving self-assembly with concomitant condensation. It was found that with increasing surfactant-to-metal ratios, new hexagonal P63/mmc (Nb-TMS2) and layered (Nb-TMS4) phases could be formed, while increasing the surfactant chain length led to a new cubic phase (Nb-TMS3). Crystals of Nb-TMS1 of up to several mm in dimensions were also grown. These crystals are larger than the biggest mesoporous crystals reported by a factor of 3 orders of magnitude. These crystals retain their structure on micelle removal by acid treatment and are thus of great interest as hosts for quantum wires.