Novel macroporous palladium cation crosslinked chitosan membranes for heterogeneous catalysis application

• Novel three-dimensional porous Pd2+ crosslinked chitosan membrane catalyst has been prepared.
• Pd2+ worked as not only the crosslinker for chitosan but also catalytic sites for reactions.
• The reductive palladium species in the membrane catalysts was in the nanometer scale (20–40 nm).
• The Pd@PCSM catalyst exhibited excellent activity and stability for Heck coupling reactions.

A novel palladium supported on chitosan porous membrane heterogeneous catalyst has been prepared by freeze-drying of Pd2+-crosslinked chitosan gel solution. The prepared membrane catalyst has three-dimensional porous structure (porosity: >70%). The crosslinking effects of Pd2+ to chitosan were good for the improvement of the mechanical properties and thermal stabilities. Pd2+ cations have been shown not only as the crosslinker, but also as the catalytic active sites. The reductive palladium species of the recycled membrane catalysts was found in the nanometer scale (20–40 nm). Excellent cross-coupling yields were achieved using as low as 0.12 mol% palladium catalyst loading for the Heck-type reaction of aromatic halides with acrylates. The catalyst could be recycled six times without obvious decreased conversion.