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- 저자 : Hirscher, Michael (검색결과 3 건)
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Magnetic Behavior of Single-Chain Magnets in Metal Organic Frameworks CPO-27-Co
Son, Kwanghyo,Goering, Eberhard,Hirscher, Michael,Oh, Hyunchul American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.10
<P>Nanoscale molecular magnets of highly porous and crystalline Metal-organic frameworks (MOFs) have attracted increasing interest in recent years because of their potential application in nano-magnetic device or matrices for encapsulating of a large variety of substances. For that, a fundamental understanding of its origin of magnetism in MOFs would be essential and will provide useful insight for intelligent design of their electromagnetic properties (e.g., single-chain magnets, single-ion magnets or single-molecule magnets). Herein, we experimentally investigate the magnetic property of hexagonal 1-D channel MOFs composed of metal(cobalt) cluster connected with organic linker (so-called CPO-27-Co). Through a fundamental physisorption analysis, in-depth magnetic studies by use of superconducting quantum interference device (SQUID) magnetometry, and theoretically by the application of an isotropic Heisenberg Hamiltonian, we found a magnetic configuration of CPO-27-Co exhibiting both a weak ferro-and antiferromagnetism with cobalt magne-tocrystalline anisotropy. Interestingly, when a magnetic configuration of cobalt cluster (instead of ionic cobalt inside cluster of CPO-27) are considered, the inter Co cluster interaction exhibits superparamagnetic behavior while inside of Co cluster (ionic Co-Co interaction) is dominated by a weak ferromagnetic component.</P>
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Selective Hydrogen Isotope Separation via Breathing Transition in MIL-53(Al)
Kim, Jin Yeong,Zhang, Linda,Balderas-Xicohté,ncatl, Rafael,Park, Jaewoo,Hirscher, Michael,Moon, Hoi Ri,Oh, Hyunchul American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.49
<P>Breathing of MIL-53(Al), a flexible metal–organic framework (MOF), leads to dynamic changes as narrow pore (<I>np</I>) transitions to large pore (<I>lp</I>). During the flexible and reversible transition, the pore apertures are continuously adjusted, thus providing the tremendous opportunity to separate mixtures of similar-sized and similar-shaped molecules that require precise pore tuning. Herein, for the first time, we report a strategy for effectively separating hydrogen isotopes through the dynamic pore change during the breathing of MIL-53(Al), a?representative of flexible MOFs. The experiment shows that the selectivity for D<SUB>2</SUB> over H<SUB>2</SUB> is strongly related to the state of the pore structure of MIL-53(Al). The highest selectivity (<I>S</I><SUB>D<SUB>2</SUB>/H<SUB>2</SUB></SUB> = 13.6 at 40 K) was obtained by optimizing the exposure temperature, pressure, and time to systematically tune the pore state of MIL-53(Al).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2017/jacsat.2017.139.issue-49/jacs.7b10323/production/images/medium/ja-2017-10323j_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja7b10323'>ACS Electronic Supporting Info</A></P>
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Kim, Jin Yeong,Balderas-Xicohté,ncatl, Rafael,Zhang, Linda,Kang, Sung Gu,Hirscher, Michael,Oh, Hyunchul,Moon, Hoi Ri American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.42
<P>Deuterium plays a pivotal role in industrial and scientific research, and is irreplaceable for various applications such as isotope tracing, neutron moderation, and neutron scattering. In addition, deuterium is a key energy source for fusion reactions. Thus, the isolation of deuterium from a physico-chemically almost identical isotopic mixture is a seminal challenge in modern separation technology. However, current commercial approaches suffer from extremely low separation efficiency (i.e., cryogenic distillation, selectivity of 1.5 at 24 K), requiring a cost-effective and large-scale separation technique. Herein, we report a highly effective hydrogen isotope separation system based on metal–organic frameworks (MOFs) having the highest reported separation factor as high as ∼26 at 77 K by maximizing synergistic effects of the chemical affinity quantum sieving (CAQS) and kinetic quantum sieving (KQS). For this purpose, the MOF-74 system having high hydrogen adsorption enthalpies due to strong open metal sites is chosen for CAQS functionality, and imidazole molecules (IM) are employed to the system for enhancing the KQS effect. To the best of our knowledge, this work is not only the first attempt to implement two quantum sieving effects, KQS and CAQS, in one system, but also provides experimental validation of the utility of this system for practical industrial usage by isolating high-purity D<SUB>2</SUB> through direct selective separation studies using 1:1 D<SUB>2</SUB>/H<SUB>2</SUB> mixtures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2017/jacsat.2017.139.issue-42/jacs.7b07925/production/images/medium/ja-2017-079254_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja7b07925'>ACS Electronic Supporting Info</A></P>
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