title: Hybrid Coordination Networks Constructed from ɛ-Keggin-Type Polyoxometalates and Rigid Imidazole-Based Bridging Ligands as New Carriers for Noble-Metal Catalysts.
abstract: Three hybrid coordination networks that were constructed from ɛ-Keggin polyoxometalate building units and imidazole-based bridging ligands were prepared under hydrothermal conditions, that is, H[(Hbimb)2 (bimb){Zn4 PMo(V8) Mo(VI) 4O40}]⋅6 H2O(1), [Zn(Hbimbp)(bimbp)3 {Zn4 PMo(V8) Mo(VI) 4O40}]⋅DMF⋅3.5 H2O(2), and H[Zn2 (timb)2 (bimba)2 Cl2 {Zn4 PMo(V8) Mo(VI) 4O40}]⋅7 H2O(3) (bimb=1,4-bis(1-imidazolyl)benzene, bimbp=4,4'-bis(imidazolyl)biphenyl, timb=1,3,5-tris(1-imidazolyl)benzene, bimba=3,5-bis(1-imidazolyl)benzenamine). All three compounds were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. The mixed valence of the Mo centers was analyzed by XPS spectroscopy and bond-valence sum calculations. In all three compounds, the ɛ-Keggin polyoxometalate (POM) units acted as nodes that were connected by rigid imidazole-based bridging ligands to form hybrid coordination networks. In compound 1, 1D zigzag chains extended to form a 3D supramolecular architecture through intermolecular hydrogen-bonding interactions. Compound 2 consisted of 2D curved sheets, whilst compound 3 contained chiral 2D networks. Because of the intrinsic reducing properties of ɛ-Keggin POM species, noble-metal nanoparticles were loaded onto these POM-based coordination networks. Thus, compounds 1-3 were successfully loaded with Ag nanoparticles, and the corresponding composite materials exhibited high catalytic activities for the reduction of 4-nitrophenol.
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China.
authors.forename: Xiao-Jian
authors.initials: XJ
authors.lastname: Yang
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China.
authors.forename: Meng
authors.initials: M
authors.lastname: Sun
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China. zanghy100@nenu.edu.cn.
authors.forename: Hong-Ying
authors.identifier: http://orcid.org/0000-0002-8148-0303
authors.initials: HY
authors.lastname: Zang
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Ma
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China. fengxiaojia003@126.com.|College of Science, Shenyang Agricultural University, Shenyang, 110866, P. R. China. fengxiaojia003@126.com.
authors.forename: Xiao-Jia
authors.initials: XJ
authors.lastname: Feng
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China.
authors.forename: Hua-Qiao
authors.initials: HQ
authors.lastname: Tan
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China. wangyh319@nenu.edu.cn.
authors.forename: Yong-Hui
authors.initials: YH
authors.lastname: Wang
authors.affiliation: Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, 130024, P. R. China.
authors.forename: Yang-Guang
authors.initials: YG
authors.lastname: Li
keywords: composite materials; nanoparticles; noble metals; polyoxometalates; reduction