Hidalgo Gabriel, Devillers Michel, Gaigneaux Eric M
Institute of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain, Place Louis Pasteur, 1, P.O. Box L4.01.09, 1348 Louvain-la-Neuve, Belgium.
Inorg Chem. 2022 Aug 15;61(32):12494-12507. doi: 10.1021/acs.inorgchem.2c00342. Epub 2022 Aug 4.
A thorough investigation of two novel hybrid materials, namely, (2,2'-Hbpy)[PWO] and (4,4'-Hbpy)[PWO]·1.5HO built from Keggin phosphotungstic acid (PTA) and bipyridine, describes the impact of bipyridine isomers in their formation and physicochemical properties. The hybrids' formation was confirmed by powder X-ray diffraction, while infrared spectroscopy (IR) proved the polyoxometalate (POM) structural preservation. The stoichiometric composition and thermal stability of the hybrids were solved by thermogravimetric analysis-mass spectrometry, which also revealed newly acquired hydrophobic properties. Raman and IR spectroscopies demonstrated that the POM skeleton units in both hybrids were distorted compared to the POM in PTA, which induced a decrease of their reduction potentials as observed by diffuse reflectance ultraviolet-visible spectroscopy (DR-UV-vis). The hybrids' acidity was assessed by ammonia temperature-programmed desorption, which showed no remaining acid sites compared to the strong acidic character of the pristine PTA. The properties of the hybrids were tested in the epoxidation of cyclooctene in the presence of HO. The reaction was boosted when the hybrids were pre-activated with HO.
对两种新型杂化材料，即由Keggin型磷钨酸（PTA）和联吡啶构建的(2,2'-Hbpy)[PWO]和(4,4'-Hbpy)[PWO]·1.5H₂O进行了深入研究，描述了联吡啶异构体对其形成和物理化学性质的影响。通过粉末X射线衍射确认了杂化物的形成，而红外光谱（IR）证明了多金属氧酸盐（POM）结构的保留。通过热重分析-质谱法解析了杂化物的化学计量组成和热稳定性，该方法还揭示了新获得的疏水性质。拉曼光谱和红外光谱表明，与PTA中的POM相比，两种杂化物中的POM骨架单元发生了扭曲，如漫反射紫外-可见光谱（DR-UV-vis）所示，这导致它们的还原电位降低。通过氨程序升温脱附评估了杂化物的酸度，与原始PTA的强酸性特征相比，结果显示没有残留的酸性位点。在HO存在的情况下，在环辛烯环氧化反应中测试了杂化物的性能。当杂化物用HO预活化时，反应得到促进。
