类质同像置换对锰钾矿氧化异戊二烯能力的制约

锰钾矿具有强氧化性，对地球关键带的物质循环具有重要影响。与土壤和水体中的变价重金属、有机物等相比，锰钾矿对大气中异戊二烯等植物源挥发性有机物（VOCs）的氧化作用研究较为薄弱，无法掌握该矿物在植物源VOCs转化中的重要作用。特别是，锰钾矿存在多种不同微结构（八面体/孔道）的类质同像置换，很可能制约其对植物源VOCs的氧化能力。本项目拟以不同成因的天然锰钾矿为主要研究对象，以合成系列典型类质同像置换锰钾矿为对比研究对象，利用谱学、微束、微区等技术表征置换离子的微观局域环境，考察不同锰钾矿对异戊二烯的氧化能力和反应机理，阐释天然锰钾矿晶体化学特征对异戊二烯氧化能力的控制作用，建立置换离子微观局域环境、锰钾矿表面物理化学性质与氧化异戊二烯能力的结构-效能关系，从原子水平揭示类质同像置换对锰钾矿氧化异戊二烯能力的制约机制，所获认识有助于理解和掌握锰钾矿在植物源VOCs迁移-转化过程中的作用和角色。

The strong oxidization property of cryptomelane has a great impact on the substance circulation in the earth’s critical zone. The cryptomelane has been widely studied in the oxidation of multivalent heavy metals, organic matters, etc. in the soil and water. However, less attention has been paid on the oxidation of plant-derived volatile organic compounds (VOCs) by cryptomelane in the atmosphere, such as isoprene. The importance of cryptomelane in the transfer and transformation process of plant-derived VOCs is still ambiguous. In particular, there are several main isomorphous substitutions in cryptomelane, such as substitution in octahedral and tunnel sites, which may cause different performance on the oxidation of plant-derived VOCs. In this project, the natural cryptomelane with different genesis is the main research objective, while the synthesized cryptomelane with typical substituted ions is for comparison. The local structure around substituted ions is characterized by various spectroscopy, microbeam, and microzone techniques. The oxidation of isoprene by cryptomelane is investigated on activity and reaction mechanism. This study aims to elucidate the correlation between crystal-chemical characteristics and the activity of isoprene oxidation over natural cryptomelane. The relationship among the local structure around substituted ions, surface physico-chemical properties of cryptomelane, and the activity of isoprene oxidation is built to uncover the constraints of isomorphous substitution in cryptomelane on the oxidation of isoprene at the atomic level. The obtained results will be beneficial for the profound understanding of the cryptomelane in the transformation and transfer process of plant-derived VOCs.