Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of the American Chemical Society  

Triplet carbenes (TCs) are of great interest due to their magnetic properties and reactivity, which descend from TCs' unique electronic state. However, the reactivity and stability of TCs are usually a trade-off, and it is difficult to achieve both at the same time. In this work, we were able to enhance the thermal stability of a TC species while maintaining its reactivity by confining them in the nanospace of a metal-organic framework (MOF). We synthesized a new MOF using a TC precursor; subsequently, TCs were generated by photostimulation. The TCs generated in the MOF nanospace were detectable up to 170 K, whereas their non-MOF-confined counterparts (bare ligand) could not be detected above 100 K. In addition, the reactivity of TC generated in MOF with O2 was drastically improved compared to that of bare ligand. Our approach is generally applicable to the stabilization of highly reactive species, whose reactivity needs to be preserved.

DOI： 10.1021/jacs.1c02430

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Nanoporous materials can adsorb small molecules into their nanospaces. However, the trapping of light gas molecules dissolved in solvents suffers from low concentration and poor adsorption affinity. Here, the reversible trapping and releasing of dissolved oxygen are shown through integrating photosensitization and chemical capturing abilities into a metal–organic framework (MOF), MOMF-1. 9,10-Di(4-pyridyl)anthracene (dpa) ligands in MOMF-1 generates singlet oxygen from triplet oxygen under photoirradiation without additional photosensitizers, and successively reacts with it to produce anthracene endoperoxide, forming MOMF-2, which is proved crystallographically. The reverse reaction also proceeds quantitatively by heating MOMF-2. Moreover, MOMF-1 exhibits excellent water resistance, and completely removes oxygen of ppm order concentrations in water. The new material shown in this report allows controlling of the amount of dissolved oxygen, which can be applicable in various fields relating to numerous oxidation phenomena.

DOI： 10.1002/smll.202004351

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/smll.202004351

Language：English   Publisher：Small  

Electrochemical reduction of CO2 in aqueous media is an important reaction to produce value-added carbon products in an environmentally and economically friendly manner. Various molecule-based catalytic systems for the reaction have been reported thus far. The key features of state-of-the-art catalytic systems in this field can be summarized as follows: 1) an iron-porphyrin-based scaffold as a catalytic center, 2) a dinuclear active center for the efficient activation of a CO2 molecule, and 3) a hydrophobic channel for the accumulation of CO2. This article reports a novel approach to construct a catalytic system for CO2 reduction with the aforementioned three key substructures. The self-assembly of a newly designed iron-porphyrin complex bearing bulky substituents with noncovalent interaction ability forms a highly ordered crystalline solid with adjacent catalytically active sites and hydrophobic pores. The obtained crystalline solid serves as an electrocatalyst for CO2 reduction in aqueous media. Note that a relevant iron-porphyrin complex without bulky substituents cannot form a porous structure with adjacent active sites, and the catalytic performance of the crystals of this relevant iron-porphyrin complex is substantially lower than that of the newly developed catalytic system. The present study provides a novel strategy for constructing porous crystalline solids for small-molecule conversions.

DOI： 10.1002/smll.202006150

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

<p>Here we report enhanced CO₂ molecular recognition ability by incorporating insertion reaction into a metal porphyrin complex in a metal-organic framework (MOF). PCN-222(Cu)-INA was synthesized by the reaction of PCN-222(Cu) [Zr₆O₈(H₂O)₈(Cu-TCPP)₂], where Cu-TCPP = Cu(II) tetrakis(4-carboxyphenyl)porphyrin, and isonicotinic acid (INA). PCN-222(Cu)-INA exhibited a 1.5 times larger CO₂ adsorption amount than PCN-222(Cu) at 298 K and 1 bar. The mechanism involving insertion reaction of CO₂ into Cu–N bonds enhanced the adsorption, which was revealed by <i>in situ</i> IR spectroscopy and theoretical calculations.</p>

DOI： 10.1246/cl.200785

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/jacs.0c13310

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

<p>Molecular motions taking place in the nanospace of metal–organic frameworks (MOFs) are an interesting research subject, although not yet fully investigated. In this work, we utilized in situ Raman spectroscopy...</p>

DOI： 10.1039/d0fd00002g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

DOI： 10.1039/d0cc00932f

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>OMSs in HKUST-1 can strongly trap DMS even under humid conditions, which was directly proved by <italic>in situ</italic> single-crystal X-ray diffraction and Raman measurements.</p>

DOI： 10.1039/c9ra09702c

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/jacs.9b07682

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c9cp04625a

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A layered metal-organic framework (MOF) comprising extra-large nanographene sheets, (MOF)-M-HBC, was successfully synthesized using a dicarboxylic acid derivative of hexa-perihexab enzocoronene ((LH2)-L-HBC), and its structure was characterized by single-crystal X-ray diffraction analysis. The crystal structure shows that 2D layers composed of a dinuclear Zn2+ complex unit and L-HBC are located on top of each other through multiple weak interlayer bonds, affording (MOF)-M-HBC, having three dimensionally connected nanopores with large nanographene surfaces. The HBC-based nanographene sheets are anchored to the MOF framework via two zinc carboxylate linkages and therefore have an axial rotational freedom. The sorption isotherms of gaseous molecules such as carbon dioxide and hydrocarbons (acetylene, propane, propylene, benzene, and cyclohexane) on (MOF)-M-HBC all displayed a hysteretic profile with reversible structural changes, as observed by in situ powder X-ray diffraction studies.

DOI： 10.1021/jacs.9b07732

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Language：Japanese   Publishing type：Research paper (scientific journal)  

In this study, we report a facile ligand-assisted in situ hydrothermal approach for preparation of compact [Al(OH)(1,4-NDC)] (1,4-NDC=1,4-naphthalenedicarboxylate) MOF membranes on porous γ-Al2 O3 substrates, which also served as the Al3+ source of MOF membranes. Simultaneously, it was observed that the heating mode exerted significant influence on the final microstructure and separation performance of [Al(OH)(1,4-NDC)] membranes. Compared with the conventional hydrothermal method, the employment of microwave heating led to the formation of [Al(OH)(1,4-NDC)] membranes composed of closely packed nanorods with superior H2 /CH4 selectivity.

DOI： 10.1002/asia.201900152

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c8dt04218g

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Language：Japanese   Publishing type：Research paper (scientific journal)  

The ability of porous coordination polymers to undergo reversible structural transformations in response to the presence of guest molecules has been intensively investigated for applications such as molecular separation, storage, sensing and signalling processes. Here we report on the direct observation of the highly guest-responsive nature of the surface of a single-crystalline porous coordination polymer, which consists of paddlewheel zinc clusters and two types of ligand, by in situ liquid-phase atomic force microscopy. Observations were carried out in solution at constant temperature (28 °C) by high-speed atomic force microscopy with lattice resolution. A sharp and reversible response to the presence or absence of biphenyl guest molecules was observed, under conditions that can scarcely induce the transformation of the bulk crystal. Additionally, by modulating the surface coordination equilibrium, layer-by-layer delamination events were captured in real time at every ~13 s per frame.

DOI： 10.1038/s41557-018-0170-0

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Design of the gas-diffusion process in a porous material is challenging because a contracted pore aperture is a prerequisite, whereas the channel traffic of guest molecules is regulated by the flexible and dynamic motions of nanochannels. Here, we present the rational design of a diffusion-regulatory system in a porous coordination polymer (PCP) in which flip-flop molecular motions within the framework structure provide kinetic gate functions that enable efficient gas separation and storage. The PCP shows substantial temperature-responsive adsorption in which the adsorbate molecules are differentiated by each gate-admission temperature, facilitating kinetics-based gas separations of oxygen/argon and ethylene/ethane with high selectivities of ~350 and ~75, respectively. Additionally, we demonstrate the long-lasting physical encapsulation of ethylene at ambient conditions, owing to strongly impeded diffusion in distinctive nanochannels.

DOI： 10.1126/science.aar6833

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c8ce01681j

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The gate-opening adsorption mechanism and sigmoidal adsorption isotherm were theoretically investigated taking CO, adsorption into porous coordination polymers, [Fe(ppt)(2)](n) (PCP-N, Hppt = 3-(2-pyrazinyl)-5-(4-pyridyl)-1,2,4-triazole) and [Fe(dpt)(2)](n) (PCP-C, Hdpt = 3-(2-pyridiny1)-5-(4-pyridy1)-1,2,4-triazole) as examples, where the hybrid method consisting of dispersion-corrected DFT or infinite PCP and a post-Hartree-Fock (SCS-MP2 and CCSD(T)) method for the cluster model was employed. PCP-N has site I (one-dimensional channel), site II (small aperture to site I), and site III (small pore) useful for CO2 adsorption. CO2 adsorption at site I occurs in a one by one manner with a Langmuir adsorption isotherm. CO2 adsorption at sites II and III occurs through a gate-opening adsorption mechanism, because the crystal deformation energy (EDEF) at these sites is induced largely by the first CO2 adsorption but induced much less by the subsequent CO2 adsorption. Interestingly, nine CO2 molecules are adsorbed simultaneously at these sites because a large EDEF cannot be overcome by adsorption of one CO2 molecule but can be by simultaneous adsorption of nine CO2 molecules. For such CO2 adsorption, the Langmuir-Freundlich sigmoidal adsorption isotherm was derived from the equilibrium equation for CO2 adsorption. A very complicated CO2 adsorption isotherm, experimentally observed, is reproduced by combination of the Langmuir and Langmuir Freundlich adsorption isotherms. In PCP-C, CO2 adsorption occurs only at site I with the Langmuir adsorption isotherm. Sites II and III of PCP-C cannot be used for CO2 adsorption because a very large EDEF cannot be overcome by simultaneous adsorption of nine CO2 molecules. Factors necessary for gate-opening adsorption mechanism are discussed on the basis of differences between PCP-N and PCP-C.

DOI： 10.1021/jacs.8b09358

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c8sc02263a

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Language：English   Publishing type：Research paper (scientific journal)  

Herein, we report that a new flexible coordination network, NiL2 (L=4-(4-pyridyl)-biphenyl-4-carboxylic acid), with diamondoid topology switches between non-porous (closed) and several porous (open) phases at specific CO2 and CH4 pressures. These phases are manifested by multi-step low-pressure isotherms for CO2 or a single-step high-pressure isotherm for CH4 . The potential methane working capacity of NiL2 approaches that of compressed natural gas but at much lower pressures. The guest-induced phase transitions of NiL2 were studied by single-crystal XRD, in situ variable pressure powder XRD, synchrotron powder XRD, pressure-gradient differential scanning calorimetry (P-DSC), and molecular modeling. The detailed structural information provides insight into the extreme flexibility of NiL2 . Specifically, the extended linker ligand, L, undergoes ligand contortion and interactions between interpenetrated networks or sorbate-sorbent interactions enable the observed switching.

DOI： 10.1002/anie.201800820

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Kinetic stabilisation of unstable chemical species in nanospace is of potential importance in the field of materials and synthetic chemistry, and porous coordination polymers (PCPs) represent a facile platform to provide such reaction fields. Thiyl radicals are important reactive substances that often play a leading role in organic and bioorganic chemistry. However, their generation in nanospace has been barely investigated due to synthetic difficulties. Here, we report a facile methodology for the functionalisation of active thiyl substituents on PCP pore surfaces using a post-synthetic protection and deprotection technique. The thiyl radicals were generated inside a zinc(ii)-based PCP upon the deprotection of asymmetric disulfides, which were used as the protecting groups by ultraviolet light irradiation.

DOI： 10.1039/c8cc01837e

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Two porous coordination polymers (PCPs) with different topologies (NTU-19: sql and NTU-20: dia) underwent finely controlled, stepwise crystal conversions to yield a common water-stable, flexible 2D framework (NTU-22: kgm). The crystal conversions occurred directly at higher temperature via the 3D intermediate (NTU-21: nbo), which could be observed at lower temperature. The successful isolation of the intermediate product of NTU-21, characterization with in situ PXRD and UV/Vis spectra were combined with DFT calculations to allow an understanding of the dynamic processes at the atomic level. Remarkably, breakthrough experiments demonstrate NTU-22 with integral structural properties allowed significant CO2 /CH4 mixture separation.

DOI： 10.1002/chem.201705858

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Shape-memory effects are quite well-studied in general, but there is only one reported example in the context of porous materials. We report the second example of a porous coordination network that exhibits a sorbate-induced shape-memory effect and the first in which multiple sorbates, N2, CO2 and CO promote this effect. The material, a new threefold interpenetrated pcu network, [Zn2(4,4'-biphenyldicarboxylate)2(1,4-bis(4-pyridyl)benzene)]n (X-pcu-3-Zn-3i), exhibits three distinct phases: the as-synthesized α phase; a denser-activated β phase; and a shape-memory γ phase, which is intermediate in density between the α and β phases. The γ phase is kinetically stable over multiple adsorption/desorption cycles and only reverts to the β phase when heated at >400 K under vacuum. The α phase can be regenerated by soaking the γ phase in N,N'-dimethylformamide. Single-crystal x-ray crystallography studies of all three phases provide insight into the shape-memory phenomenon by revealing the nature of interactions between interpenetrated networks. The β and γ phases were further investigated by in situ coincidence powder x-ray diffraction, and their sorption isotherms were replicated by density functional theory calculations. Analysis of the structural information concerning the three phases of X-pcu-3-Zn-3i enabled us to understand structure-function relationships and propose crystal engineering principles for the design of more examples of shape-memory porous materials.

DOI： 10.1126/sciadv.aaq1636

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Here we report a soft porous crystal possessing hemilabile cross-links in its framework that exhibits exclusive gate opening for ethylene, enabling the discriminatory adsorption of ethylene over ethane. A Co-based porous coordination polymer (PCP) bearing vinylogous tetrathiafulvalene (VTTF) ligands, [Co(VTTF)], forms Co-S bonds as intermolecular cross-links in its framework in the evacuated closed state. The PCP recognizes ethylene via d-pi complexation on the accessible metal site that displaces and cleaves the Co-S bond to "unlock" the closed structure. This ethylene-triggered unlocking event facilitates remarkable nonporous-to-porous transformations that open up accessible void space. This structural transformation follows a two-step gate-opening process. Each phase, including the intermediate structure, was successfully characterized by single-crystal X-ray diffraction analysis, which revealed an intriguing "half-open" structure suggestive of a disproportionate gate-opening phenomenon. The gate-opening mechanism was also investigated theoretically; density functional theory and Monte Carlo calculations revealed that the unique "half-open" phase corresponds to a substantially stable intermediate over the possible transformation trajectories. While ethylene opens the gate, ethane does not . because it is unable to coordinate to the Co center. This feature is maintained even at pressures above 1 MPa and at a temperature of 303 K, demonstrating the potential of the "gate-locking/unlocking" mechanism that exploits the hemilabile cross-linking in soft porous crystals.

DOI： 10.1021/jacs.7b10110

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A new porous coordination polymer (PCP) based on a ligand with a unique bent angle bearing a thiophene-bridged bent carboxylate ligand and the Cu2+ ion was synthesized and structurally characterized. The structure has a pillared-layer framework based on a kagome-like layer with aromatic partition groups. It exhibits a high CO2 uptake of 180 mL(STP)/g at 1 bar, and 400 mL(STP)/g at 30 bar at 273 K. The uptakes of C2H2 and C2H4 reach 164 and 160 mL(STP)/g at 298 K and 1 bar, with good selectivity of C2H2 and C2H4 over CH4, both of which are among the highest levels of reported PCPs.

DOI： 10.1021/acsami.7b01568

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Adsorptions of CO, N-2, NO, and CO2 in a paddle-wheel type porous coordination polymer (PCP) [Cu(aip)] (aip = 5-azidoisophthalate) were investigated with ONIOM[MP4(SDQ):omega B97XD] method using a model system consisting of two [Cu-2(O2CC6H4-R)(4)] units (R = H and Me) and one [Cu-2(O2CC6H4R)(4)] unit, namely, dimer and monomer models. The experimental CO adsorption position was reproduced well by the present calculation with the dimer model. For adsorptions of CO, N-2, NO, and CO2 in the dimer model, the position of gas molecule deviates from the normal one that is found in the monomer model and becomes more distant from the surrounding phenyl group(s) of the neighbor [Cu(aip)] unit. For all of these gas molecules, the calculated binding energy (BE) at the deviating adsorption position is larger than that at the normal one against our expectation that the normal position is the best for the gas adsorption. The deviation of gas adsorption position arises from the interaction between the organic linker (O2CC6H4-R moiety) and gas molecule. For all cases, the exchange repulsion with the organic linker decreases to a larger extent than the attractive electrostatic and dispersion interactions decrease when going from the normal position to the deviating one. To enhance the binding energy of gas molecule, the introduction of electron-donating substituent on phenyl moiety is computationally recommended for this PCP.

DOI： 10.1021/acs.jpcc.7b02707

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Nano-porous coordination polymers (nano-PCPs), as a new class of crystalline material, have become a lucrative topic in coordination chemistry due to the facile tunability of their functional pore environments. However, elucidating the pathways for the rational design and preparation of nano-PCPs with various integrated properties for feasible gas separation remains a great challenge. Here, we demonstrate a new route to achieve nano-PCPs with an integrated pore system and physical properties using a reticular chemistry strategy. By optimizing the position and length of the shortest two alkyl groups in the channels, unprecedented phenomena of improved surface area, gas uptake, gas selectivity, thermal stability and chemical stability were observed in the PCPs, especially in NTU-14, the structure with a pendant ethyl group. Furthermore, the high performance of adsorption-and membrane-based separation makes NTU-14 a promising medium for CH4 purification from a mixture at room temperature.

DOI： 10.1039/c7ta02760e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The prevalence of the condensed phase, interpenetration, and fragility of ruesoporous coordination polymers (meso-PCPs) featuring dense open metal sites (OMSs) place strict limitations en their preparation, as revealed by experimental and `theoretical reticular chemistry investigations. Herein, we propose a rational design of stabilized high-porosity meso-PCPs, employing a 'low-symmetry ligand in combination with the shortest linker, formic acid. The resulting dimeric dusters (PCP-31 and PCP-32) exhibit high surface areas, ultrahigh porosities, and high OMS derisities (3.76 and 3.29 nmol g(-1) respectively), enabling highly selective- and effective separation of C2H2 from C2H2/CO2 mixtures at 298 K, as verified by binding energy (BE) and electrostatic potentials (ESP) calculations.

DOI： 10.1021/jacs.7b05702

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DOI： 10.1002/anie.201611785

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

New bis(dipyrrinato) zinc(II) complex micro- and nanosheets containing zinc(II) porphyrin (N2) are synthesized. A liquid/liquid interface method between dipyrrin porphyrin ligand L2 and zinc acetate produces N2 with a large domain size. N2 can be layered quantitatively onto a flat substrate by a modified Langmuir-Schafer method. N2 deposited on a SnO2 electrode functions as a photoanode for a photoelectric conversion system. The photoresponse of N2 covers the whole visible wavelength range (400-650 nm), with a maximum quantum efficiency of more than twice that of a bis(dipyrrinato) zinc(II) complex nanosheet without porphyrin.

DOI： 10.1002/ange.201611785

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DOI： 10.1126/science.aar6833

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DOI： 10.1021/jacs.8b09358

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DOI： 10.1039/c8sc02263a

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DOI： 10.1002/anie.201800820

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DOI： 10.1039/c8cc01837e

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DOI： 10.1002/chem.201705858

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DOI： 10.1126/sciadv.aaq1636

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DOI： 10.1021/acsami.7b01568

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DOI： 10.1039/c7ta02760e

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Language：Japanese   Publisher：技術情報協会  

CiNii Books

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DOI： 10.1002/anie.201611785

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DOI： 10.1021/jacs.6b02128

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DOI： 10.1002/anie.201509411

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DOI： 10.1021/jacs.5b09666

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DOI： 10.1038/ncomms7713

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DOI： 10.1021/ic500326u

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DOI： 10.1039/c4cc01573h

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DOI： 10.5796/electrochemistry.81.337

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DOI： 10.3390/molecules18044091

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DOI： 10.1002/asia.201201176

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DOI： 10.1002/asia.201200131

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DOI： 10.1002/hc.20630

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DOI： 10.1002/anie.200803945

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