title: Structural Distortion of Molybdenum-Doped Manganese Oxide Octahedral Molecular Sieves for Enhanced Catalytic Performance.
abstract: Due to the excellent catalytic performance of manganese oxide (K-OMS-2) in a wide range of applications, incorporation of various dopants has been commonly applied for K-OMS-2 to acquire additional functionality or activities. However, the understanding of its substitution mechanism with respect to the catalytic performance of doped K-OMS-2 materials remains unclear. Here we present the structural distortion (from tetragonal to monoclinic cell) and morphological evolution in K-OMS-2 materials by doping hexavalent molybdenum. With a Mo-to-Mn ratio of 1:20 (R-1:20) in the preparation, the resultant monoclinic K-OMS-2 shows a small equidimensional particle size (∼15 nm), a high surface area of 213 m(2) g(-1), and greatly improved catalytic activity toward CO oxidation with lower onset temperatures (40 °C) than that of pristine K-OMS-2 (above 130 °C). HR-TEM analyses reveal direct evidence of structural distortion on the cross-section of 2 × 2 tunnels with the absence of 4-fold rotation symmetry expected for a tetragonal cell, which are indexed using a monoclinic cell. Our results suggest that substitution of Mo(6+) for Mn(3+) (rather than Mn(4+)) coupled with the vacancy generation results in a distorted structure and unique morphology. The weakened Mn-O bonds and Mn vacancies associated with the structural distortion may be mainly responsible for the enhanced catalytic activity of monoclinic K-OMS-2 instead of dopant species.
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.|Department of Chemistry, National Sun Yat-sen University , Kaohsiung, Taiwan 80424, United States.
authors.forename: Chun-Hu
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Njagi
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Sheng-Yu
authors.initials: SY
authors.lastname: Chen
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Dayton T
authors.initials: DT
authors.lastname: Horvath
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Linping
authors.initials: L
authors.lastname: Xu
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.|Department of Chemistry, United States Air Force Academy , Colorado Springs, Colorado 80840, United States.
authors.forename: Aimee
authors.initials: A
authors.lastname: Morey
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Charles
authors.initials: C
authors.lastname: Mackin
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Raymond
authors.initials: R
authors.lastname: Joesten
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269, United States.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Suib