Novel macroporous palladium cation crosslinked chitosan membranes for heterogeneous catalysis application

Area of Science:

• Materials Science
• Catalysis
• Green Chemistry

Background:

• Heterogeneous catalysis offers advantages in catalyst separation and reusability.
• Chitosan is a biocompatible and biodegradable polymer with potential for catalyst support.
• Palladium catalysts are crucial for various organic transformations, including cross-coupling reactions.

Purpose of the Study:

• To develop a novel palladium-supported chitosan porous membrane heterogeneous catalyst.
• To investigate the structural and catalytic properties of the prepared membrane catalyst.
• To evaluate the catalyst's performance in Heck-type reactions and its recyclability.

Main Methods:

• Preparation of a palladium-crosslinked chitosan gel solution.
• Freeze-drying technique to form a three-dimensional porous membrane catalyst.
• Characterization of the membrane's porosity, mechanical, and thermal properties.
• Application of the catalyst in Heck-type reactions of aromatic halides with acrylates.

Main Results:

• The catalyst exhibited a high porosity (>70%) and improved mechanical and thermal properties due to Pd(2+) crosslinking.
• Palladium species were observed in the nanometer scale (20-40nm) on the recycled catalysts.
• Excellent cross-coupling yields were achieved with low palladium loading (0.12 mol%).
• The catalyst demonstrated high stability and could be recycled six times without significant loss of conversion.

Conclusions:

• The palladium-supported chitosan porous membrane is an effective and recyclable heterogeneous catalyst.
• The Pd(2+)-crosslinked chitosan membrane offers enhanced stability and catalytic activity.
• This catalyst presents a promising green chemistry approach for efficient cross-coupling reactions.