1. Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong SAR P. R. China
2. The Education Ministry Key and International Joint Lab of Resource Chemistry Shanghai Key Lab of Rare Earth Functional Materials Shanghai Normal University Shanghai 200234 P. R. China
3. School of Materials and Chemistry University of Shanghai for Science and Technology Shanghai 200093 P. R. China
4. School of Chemistry and Chemical Engineering Yangzhou University Yangzhou 225002 P. R. China