Hydrocolloid-forming polysaccharides are natural polyelectrolytes able to form stable hydrogels largely used in the food and pharmaceutical industry. Gelling polysaccharides derived from seaweeds or wastes of the seafood industry include polymers with several functional groups: alginates (carboxylic groups), carrageenans (sulfonic groups) and chitosan (amino groups). This article deals with suitable methods to prepare dry materials which retain the dispersion of the polymer hydrogel, namely polysaccharide aerogels. The materials whose properties are herewith described satisfy most of the appropriate requirements for heterogeneous catalysts and supports: they are stable in most organic solvents, present a high surface area and diverse accessible surface functionalities. Their application as catalysts, catalyst supports or adsorbents provide a new opportunity to obtain useful materials from one of the less energy-intensive sources of biomass.

Aerogel microspheres of chitosan, an abundant biopolymer obtained from marine crustaceans, have been successfully applied to catalyze the asymmetric aldol reaction in water, providing the products in high yields and with good stereoselectivity (up to 93% ee) and recyclability (up to 4 runs). Yields were favourably affected by additives such as DNP and stearic acid.

Macroporous catalyst was obtained by dispersing nanosized gold in the fibrils of the chitosan matrix, followed by CO₂ supercritical drying of the resulting hybrid material. The accessible gold nanoparticles are highly active for carbon–carbon cross coupling reactions.