1.      Y. Du, F. Cai, D.-L. Kong, L.-N. He^*, Organic Solvent-free Process for the Synthesis of Propylene Carbonate from Supercritical Carbon Dioxide and Propylene Oxide Catalyzed by Insoluble Ion Exchange Resins, Green Chem., 2005, 7(7), 518-523. (Cover Article, “Green Chemistry”杂志2005年第七期封面论文，The fifth most popular cover art of 2005, with 56 of Cited times up to 03/2010)[link]

Abstract: The insoluble ion exchange resins, one type of polystyryl supported catalysts containing ammonium salt or amino group, and the polar macroporous adsorption resin, are efficient and reusable heterogeneous basic catalysts for the synthesis of propylene carbonate from propylene oxide and CO₂ under supercritical CO₂ conditions (373K, 8MPa), which requires no additional organic solvents either for the reaction or for the separation of product.Various reaction parameters affecting the reaction were examined. The quantitative yield (>99%) together with excellent selectivity(>99%) was obtained. The purity of product separated out directly by filtration from the reaction mixture, reached more than 99.3% without further  purification process. The catalyst can be easily recovered and reused without significant loss of its catalytic activity. The process represents a simple, ecologically safer, cost-effective route to cyclic carbonates with high product quality, as well as easy product recovery and catalyst recycle.

2.     Y. Du, D.-L. Kong, H.-Y. Wang, F. Cai, J-.S. Tian, J.-Q. Wang, L.-N. He^*, Sn-catalyzed synthesis of propylene carbonate from propylene glycol and CO₂ under supercritical conditions, J. Mol. Catal. A: Chem., 2005, 241, 233-237.[link]

Abstract: Dibutyltin oxide or dibutyltin dimethoxide was first used as a remarkable selective catalyst for the synthesis of propylene carbonate from propylene glycol and carbon dioxide. The effects of the reaction parameters such as reaction time, temperature and CO₂ pressure on the amount of propylene carbonate were also experimentally studied. Under the optimized conditions, the amount of propylene carbonate was nearly proportional to PG concentration. The use of N, N-dimethylformamide as a co-solvent in this study significantly enhanced the catalytic activity, and the ketals as dehydrating agents greatly improved the yield of PC, which can be limited by the equilibrium. A postulated mechanism for the dibutyltin oxide–catalyzed carboxylation of propylene glycol was also discussed.

3.  H. Yasuda, L.-N. He, T. Sakakura, Efficient synthesis of cyclic carbonate from carbon dioxide catalyzed by poly-oxometalate: remarkable effects of metal substitution, J. Catal., 2005, 233, 119-122.[link]