Manganese Oxide Octahedral Molecular Sieves (OMS-2) Multiple Framework Substitutions: A New Route to OMS-2 Particle Size and Morphology Control

被引:166
作者
King'ondu, Cecil K. [1 ]
Opembe, Naftali [1 ]
Chen, Chun-hu [1 ]
Ngala, Katana [1 ]
Huang, Hui [1 ]
Iyer, Aparna [1 ]
Garces, Hector F. [2 ]
Suib, Steven L. [1 ,2 ]
机构
[1] Univ Connecticut, Dept Chem, Storrs, CT 06269 USA
[2] Univ Connecticut, Inst Mat Sci, Storrs, CT 06269 USA
关键词
EFFECTIVE IONIC-RADII; LARGE-SCALE; CRYPTOMELANE; OXIDATION; HOLLANDITE; ALPHA-MNO2; MECHANISM; DIOXIDE; NANOMATERIALS; SPECTROSCOPY;
D O I
10.1002/adfm.201001020
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Self-assembled multidoped cryptomelane hollow microspheres with ultrafine particles in the size range of 4-6 nm, and with a very high surface area of 380 m(2) g(-1) have been synthesized. The particle size, morphology, and the surface area of these materials are readily controlled via multiple framework substitutions. The X-ray diffraction and transmission electron microscopy (TEM) results indicate that the as-synthesized multidoped OMS-2 materials are pristine and crystalline, with no segregated metal oxide impurities. These results are corroborated by infrared (IR) and Raman spectroscopy data, which show no segregated amorphous and/or crystalline metal impurities. The field-emission scanning electron microscopy (FESEM) studies confirm the homogeneous morphology consisting of microspheres that are hollow and constructed by the self-assembly of pseudo-flakes, whereas energy-dispersive X-ray (EDX) analyses imply that all four metal cations are incorporated into the OMS-2 structure. On the other hand, thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC) demonstrate that the as-synthesized multidoped OMS-2 hollow microspheres are more thermally unstable than their single-doped and undoped counterparts. However, the in-situ XRD studies show that the cryptomelane phase of the multidoped OMS-2 hollow microspheres is stable up to about 450 degrees C in air. The catalytic activity of these microspheres towards the oxidation of diphenylmethanol is excellent compared to that of undoped OMS-2 materials.
引用
收藏
页码:312 / 323
页数:12
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