Design of Molecular Recognition and Adsorbents for Harmful Molecules in Water using Nanospace-Organic-Inorganic Triple Nano-structure

研究了不同烷基链长和铝含量的正烷基接枝MCM-41分子筛对烷基酚和烷基苯胺的分子选择性吸附。辛基比戊基和十二基具有更好的吸附性能。氮气和水的吸附等温线表明，辛基接枝样品在接枝的烷基链之间有大量的强疏水纳米空间。辛基接枝MCM-41高分子选择性吸附水溶液中的烷基酚：正辛基接枝MCM-41能有效地去除内分泌干扰物--壬基酚，而对t-戊基苯酚的吸附很小，对苯酚的吸附无法检测到。比较了烷基酚和烷基苯胺的分子选择性，发现分子上的亲水和疏水基团独立地影响选择性。在吸附剂中捕获的正庚基苯胺的红外光谱表明，氨基与无机孔壁上的氢键很强：分子符合有机-无机纳米结构，既与无机壁相互作用，又与有机部分相互作用。由于分子的吸附量远大于Al原子在MCM-41中的吸附量，因此Al掺杂产生的酸中心对吸附的影响不大。结论是，被离子无机表面包裹的大量高度疏水的纳米空间对于这些分子的有效吸附是重要的。

Molecular selective adsorption of alkylphenols and alkylanilines are studied for n-alkyl grafted MCM-41 with different alkyl-chain lengths and Al contents. Octyl groups gave better performance of the adsorbents than pentyl and dodecyl groups. Nitrogen and water adsorption isotherms revealed that the octyl-grafted sample has a large volume of strongly hydrophobic nanospaces between the grafted alkyl chains. Octyl-grafted MCM-41 adsorbed alkylphenols from aqueous solutions with high molecular selectivity : Nonylphenol, an endocrine disrupter, is efficiently removed by adsorption into n-octyl grafted MCM-41, while adsorption of t-amylphenol is small and that of phenol is undetectable. Comparison of molecular selectivities for alkylphenols and alkylanilines reveals that hydrophilic and hydrophobic groups on molecules independently affect the selectivity. Infrared spectra of n-heptylaniline captured in the adsorbent show that the amino groups are strongly hydrogen-bonded onto the inorganic pore walls : The molecules fit the organic-inorganic nanostructure, interacting with the inorganic walls as well as the organic moiety. Since the molecules were adsorbed with much larger amounts than that of Al atoms doped in MCM-41, the effect of the acid sites produced by Al doping on the adsorption was not large in the present case. It was concluded that large volume of highly hydrophobic nanospaces that were walled by the ionic inorganic surfaces was important for efficient adsorption of these molecules