title: Molecular ligand modulation of palladium nanocatalysts for highly efficient and robust heterogeneous oxidation of cyclohexenone to phenol.
abstract: Metallic nanoparticles are emerging as an exciting class of heterogeneous catalysts with the potential advantages of exceptional activity, stability, recyclability, and easier separation than homogeneous catalysts. The traditional colloid nanoparticle syntheses usually involve strong surface binding ligands that could passivate the surface active sites and result in poor catalytic activity. The subsequent removal of surface ligands could reactivate the surface but often leads to metal ion leaching and/or severe Ostwald ripening with diminished catalytic activity or poor stability. Molecular ligand engineering represents a powerful strategy for the design of homogeneous molecular catalysts but is insufficiently explored for nanoparticle catalysts to date. We report a systematic investigation on molecular ligand modulation of palladium (Pd) nanoparticle catalysts. Our studies show that β-functional groups of butyric acid ligand on Pd nanoparticles can significantly modulate the catalytic reaction process to modify the catalytic activity and stability for important aerobic reactions. With a β-hydroxybutyric acid ligand, the Pd nanoparticle catalysts exhibit exceptional catalytic activity and stability with an unsaturated turnover number (TON) >3000 for dehydrogenative oxidation of cyclohexenone to phenol, greatly exceeding that of homogeneous Pd(II) catalysts (TON, ~30). This study presents a systematic investigation of molecular ligand modulation of nanoparticle catalysts and could open up a new pathway toward the design and construction of highly efficient and robust heterogeneous catalysts through molecular ligand engineering.
authors.affiliation: Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Teng
authors.initials: T
authors.lastname: Xue
authors.affiliation: Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Lin
authors.affiliation: Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Chin-Yi
authors.initials: CY
authors.lastname: Chiu
authors.affiliation: Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Yongjia
authors.identifier: 0000-0002-9045-8028
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Lingyan
authors.identifier: 0000-0001-8974-2593
authors.initials: L
authors.lastname: Ruan
authors.affiliation: Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Gongming
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Zipeng
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Chain
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA.; California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Duan
authors.affiliation: Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.; California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Yu
authors.identifier: 0000-0003-1793-0741
authors.initials: Y
authors.lastname: Huang
keywords: ligand; nanocatalyst; palladium nanoparticle; turn-over number