title: Encaging Palladium Nanoparticles in Chitosan Modified Montmorillonite for Efficient, Recyclable Catalysts.
abstract: Metal nanoparticles, once supported by a suitable scaffolding material, can be used as highly efficient heterogeneous catalysts for numerous organic reactions. The challenge, though, is to mitigate the continuous loss of metals from the supporting materials as reactions proceed, so that the catalysts can be recycled multiple times. Herein, we combine the excellent chelating property of chitosan (CS) and remarkable stability of montmorillonite (MMT) into a composite material to support metal catalysts such as palladium (Pd). The in situ reduction of Pd2+into Pd0in the interstices of MMT/CS composites effectively encages the Pd0nanoparticles in the porous matrices, while still allowing for reactant and product molecules of relatively small sizes to diffuse in and out the matrices. The prepared Pd0@MMT/CS catalysts are highly active for the Heck reactions of aromatic halides and alkenes, and can be recycled 30 times without significant loss of activities. Positron annihilation lifetime analysis and other structural characterization methods are implemented to elucidate the unique compartmentalization of metal catalysts in the composite matrices. As both CS and MMT are economical and abundant materials in nature, this approach may facilitate a versatile platform for developing highly recyclable, heterogeneous catalysts containing metal nanoparticles.
authors.affiliation: Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University , Shaoxing 312000, China.
authors.forename: Minfeng
authors.initials: M
authors.lastname: Zeng
authors.affiliation: Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University , Shaoxing 312000, China.
authors.forename: Yudong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University , Shaoxing 312000, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University , Shaoxing 312000, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University , Shaoxing 312000, China.
authors.forename: Shufeng
authors.initials: S
authors.lastname: Zuo
authors.affiliation: Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University , Shaoxing 312000, China.
authors.forename: Ruokun
authors.initials: R
authors.lastname: Feng
authors.affiliation: Institute of High Energy Physics, The Chinese Academy of Science , Beijing 100049, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.affiliation: Institute of High Energy Physics, The Chinese Academy of Science , Beijing 100049, China.
authors.forename: Baoyi
authors.initials: B
authors.lastname: Wang
authors.affiliation: Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University , Shaoxing 312000, China.
authors.forename: Chenze
authors.initials: C
authors.lastname: Qi
authors.affiliation: Polymer Program, Institute of Materials Science and Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Yao
authors.initials: Y
authors.lastname: Lin
keywords: chitosan; heterogeneous catalysis; montmorillonite; palladium; positron annihilation