1. Department of Chemistry Tsinghua University Beijing 100084 P. R. China
2. College of Chemistry and Chemical Engineering Inner Mongolia University Hohhot 010021 P. R. China
3. College of Environmental Engineering Henan University of Technology Zhengzhou 450001 P. R. China
4. Key Laboratory of Preparation and Applications of Environmental Friendly Materials Jilin Normal University Changchun 130103 P. R. China
5. Institute for Advanced Study Chengdu University Chengdu 610106 P. R. China