Preparation of Porous Polysaccharides Templated by Coordination Polymer with Three-Dimensional Nanochannels

Polymerization of monosaccharide monomers usually suffers from the production of polysaccharides with ill-defined structures because of the uncontrolled random reactions among many reactive hydroxyl groups on saccharide monomers. In particular, rational synthesis of polysaccharides with porosity approximating molecular dimensions is still in its infancy, despite their usefulness as drug carriers. Here, we disclose an efficient synthetic methodology for the preparation of polysaccharides with controllable mesoporosity in the structure, utilizing [Cu₃(benzene-1,3,5-tricarboxylate)]_n (HKUST-1; 1) as templates. Cationic ring-opening polymerization of 1,6-anhydro glucose was performed in nanochannels of 1, followed by removal of the host frameworks, giving polysaccharide particles as replicas of the original molds. Nitrogen adsorption measurement revealed that the obtained polysaccharide particles contained high mesoporosity in the structure, which could be controlled systematically depending on the polymerization conditions. Because of the large specific surface area, tunable porosity and particle size, we could also demonstrate the capabilities of our polysaccharides for loading and releasing of a drug molecule and protein.