1. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, P.O. Box 165, Taiyuan 030001, P. R. China, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China, and Leibniz-Institut für Organische Katalyse an der Universität Rostock, Buchbinderstrasse 5-6, 18055 Rostock, Germany