1. Center for Nanochemistry; Beijing National Laboratory for Molecular Sciences; State Key Laboratory for Structural Chemistry of Unstable and Stable Species; College of Chemistry and Molecular Engineering; Peking University; Beijing 100871 P. R. China
2. Key Laboratory of Organic Solids; Beijing National Laboratory for Molecular Science; Institute of Chemistry; Chinese Academy of Sciences; Beijing 100190 P. R. China
3. Department of Chemistry; Tsinghua University; Beijing 100084 P. R. China
4. Department of Materials Science and Engineering; College of Engineering; Peking University; Beijing 100871 P. R. China