1. College of Chemistry and Chemical Engineering, Northwest Normal University, No. 967 Anning East Road, Lanzhou 730070, P. R. China
2. Lanzhou Petrochemical Research Center, Petrochemical Research Institute, Lanzhou 730060, P. R. China
3. Advanced Fluorine-Containing Materials, Zhejiang Normal University, Jinhua 321004, P. R. China