Hierarchically order porous lotus shaped nano-structured MnO2 through MnCO3: chelate mediated growth and shape dependent improved catalytic activity
Hierarchically order porous lotus shaped nano-structured MnO2 through MnCO3: chelate mediated growth and shape dependent improved catalytic activity
复制标题
DOI：
10.1039/c3ta11440f
复制
发表时间：
2013-08
影响因子：
--
通讯作者：
Provas Pal;S. Pahari;A. Giri;Sagar Pal;H. Bajaj;A. Panda;A. Panda
中科院分区：
文献类型：
--
作者：
Provas Pal;S. Pahari;A. Giri;Sagar Pal;H. Bajaj;A. Panda;A. Panda
针对特定形貌的层次化纳米结构的设计是一个重要的研究领域，因为它们具有形状相关的性质。本文以简单的水溶液为基络合剂(柠檬酸)促进MnCO3的生长，然后在350℃下焙烧，合成了三维分级组装的莲花状多孔MnO2，还可以通过改变螯合剂来合成棒状、球状和纳米聚集体等其他形状的MnCO3。结果表明，络合配体的几何构型和强度在可控择形合成中起着关键作用，并在此基础上讨论了可能的络合剂驱动形成机理。以分子氧为氧化剂，合成的多孔型MnO2具有良好的形状依赖性催化氧化α-Pinene合成马鞭草酮的性能。莲花状多孔二氧化锰的活性优于其他形状的二氧化锰，α-Pinene的转化率为94%，马鞭草酮的选择性为87%。在转化率和选择性方面，与文献报道的多相和均相催化剂以及块状MnO2相比，该催化剂的活性相当高。以分子氧为氧化剂，合成的莲花状MnO2对烯丙基化合物氧化生成烯酮类化合物也表现出良好的催化活性，且可重复使用。
Design of hierarchical nanostructures towards a specific morphology is an important research area due to their shape dependent properties. Here, 3D hierarchically assembled lotus shaped porous MnO2 is synthesized using a simple aqueous solution based chelating agent (citric acid) mediated growth of MnCO3 followed by calcination at 350 °C. MnCO3 in other shapes, such as rods, spheres and nano-aggregates, is also synthesized just by varying the chelating agents. It is observed that the geometry and strength of the chelating ligands has a crucial role in the controlled shape selective synthesis and based on this a probable chelating agent driven formation mechanism is discussed. The synthesized porous MnO2 shapes exhibit excellent shape dependent catalytic oxidation of α-pinene to verbenone using molecular oxygen as the oxidant. The lotus shaped porous MnO2 shows superior activity, with 94% conversion of α-pinene and 87% selectivity of verbenone, to that of other MnO2 shapes. The activity is reasonably high compared to heterogeneous as well as homogeneous catalysts reported in the literature and bulk MnO2 with respect to both their conversion and selectivity. The synthesized lotus shaped MnO2 also showed good catalytic activity towards oxidation of allylic compounds to corresponding ene–ones using molecular oxygen as oxidant and is reusable.