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论文类型：期刊论文

发表时间：2019-02-07

发表刊物：JOURNAL OF PHYSICAL CHEMISTRY C

收录刊物：SCIE、EI

卷号：123

期号：5

页面范围：3122-3129

ISSN号：1932-7447

关键字：Crystalline materials; Electronic properties; Metal ions; Metals; Organic polymers; Organometallics; Scanning probe microscopy, Ferroelectric switching; Force spectroscopy; Functional ligands; Metal organic framework; Piezoresponse force microscopy; Powder X ray diffraction; Resonance tracking; Structural understanding, Nanocrystals

摘要：Metal-organic framework (MOF) UiO-66 nanocrystals were previously believed to be piezo-/ferroelectrically inactive because of their centrosymmetric lattice symmetries [Fm (3) over barm (225)] revealed by Powder X-ray diffraction. However, via the nanoscale probing studies through the delicate dual AC resonance tracking piezoresponse force microscopy and piezoresponse force spectroscopy characterizations, our work for the first time demonstrates that UiO-66 nanocrystals show certain piezo-/ferroelectric responses. The compelling experimental and theoretical analyses disclose that the structure of UiO-66 may not be the highly centrosymmetric Fm (3) over barm (225) but a reduced symmetry form. In addition, UiO-66(Hf)-type MOF nanocrystals possess stronger piezoresponses and better ferroelectric switching behaviors than their counterparts UiO-66(Zr)-type nanocrystals. Our study can further enrich the structural understanding of UiO-66 MOF and also suggests possible design of promising electronic properties of the MOFs by judicious selection of metal ions and functional ligands.