Cryogels of carboxyalkylchitosans as a universal platform for the fabrication of composite materials.

Here we report a new simple method for fabrication of supermacroporous beads and monoliths via cross-linking of carboxyalkylated chitosan derivatives with hexamethylene diisocyanate in aqueous solution at subzero temperature. These materials provide high filtration rate and good mass-transfer that in combination with high binding capacity toward metal ions allows their application as a universal platform for fabrication of composite catalysts, sorbents, and metal-affine chromatography stationary phases. Using N-(2-carboxyethyl)chitosan (CEC), we have demonstrated that optimum chitosan carboxylation degree for cryogels synthesis is close to 1.0. Cu(II)-chelated CEC cryogels have shown high efficiency as metal-affinity sorbents for ciprofloxacin recovery. Co(II)-chelated CEC cryogels have been used for fabrication of Co(II) ferrocyanide-containing composite with the distribution coefficient for Cs of 140,000 ml/g and the adsorption capacity of ˜1 mmol/g. Composite Pd-catalysts supported on CEC cryogel provided tenfold higher reaction rate in 4-nitrophenol reduction in comparison with Pd-catalyst supported on chitosan beads.