Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 346
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Am Chem Soc ; 2020 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-32674574

RESUMO

We report the synthesis of crystalline two-dimensional covalent organic frameworks (COFs) by connecting hydroxybenzene-aldehyde and acetonitrile building blocks to form cyano-substituted benzofuran linkages. Unlike the majority of COFs that were synthesized based on condensation reactions, the COFs in this report are crystallized from irreversible cascade reactions involving consecutive cyanide migration, ring-closure, and oxidation reactions. The irreversible property endows the COFs with high chemical stability in both acid and base and allows them to be postsynthetically modified to install predesigned functionality under harsh conditions. We highlight that the functionalized COFs serve as exceptional vehicles for superprotonic conductions.

2.
Chem Commun (Camb) ; 2020 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-32700696

RESUMO

Adsorption-based xylene isomer separation is more energy efficient than conventional processes. Herein, three isostructural Hofmann-type porous coordination polymers (PCPs), {M(Pz)[Ni(CN)4]n} (M = Fe, FePzNi, Co, CoPzNi, and Ni, NiPzNi; Pz = pyrazine) were synthesized and shown to exhibit coordination-dependent lability for the selectivity toward p-xylene over m- and o-xylene.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32458545

RESUMO

Since their prediction in 1998 , guest-induced structural transitions in 3 rd generation porous coordination polymers (PCPs) have changed common understanding on the adsorption properties of porous solids. By 2009, the chemistry of local and global dynamic behavior in crystalline porous solids received tremendous interest, with the studies linked under soft porous crystals (SPCs) . Since then, another decade has passed and novel phenomena in SPCs have emerged that require evaluation, particularly regarding their host-guest chemistry. In this contribution, we discuss the fundamental chemistry of SPCs by characterizing their common structural features and the resulting structural softness and transitions. In particular, we focus on the recently emerging properties based on metastable transitions and those arising from local dynamics. By comparing the resulting adsorption properties to those of commonly applied rigid adsorbents, we highlight the potential of SPCs to revolutionize adsorption-based technologies, considering our current understanding of the thermodynamic and kinetic aspects. We provide brief outlines for the experimental and computational characterization of such phenomena and offer an outlook toward next generation SPCs likely to be discovered in the next decade.

4.
Artigo em Inglês | MEDLINE | ID: mdl-32237191

RESUMO

To achieve unique molecular-recognition patterns, a rational control of the flexibility of porous coordination polymers (PCPs) is highly sought, but it remains elusive. From a thermodynamic perspective, the competitive relationship between the structural deformation energy (Edef ) of soft PCPs and the guest interaction is key for selective a guest-triggered structural-transformation behavior. Therefore, it is vital to investigate and control Edef to regulate this competition for flexibility control. Driven by these theoretical insights, we demonstrate an Edef -modulation strategy via encoding inter-framework hydrogen bonds into a soft PCP with an interpenetrated structure. As a proof of this concept, the enhanced Edef of PCP enables a selective gate-opening behavior toward CHCl3 over CH2 Cl2 by changing the adsorption-energy landscape of the compounds. This study provides a new direction for the design of functional soft porous materials.

5.
Angew Chem Int Ed Engl ; 59(1): 172-176, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31595640

RESUMO

Single-ligand-based electronically conductive porous coordination polymers/metal-organic frameworks (EC-PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π-conjugated EC-MOF containing copper units with mixed trigonal ligands was developed: Cu3 (HHTP)(THQ) (HHTP=2,3,6,7,10,11-hexahydrotriphenylene, THQ=tetrahydroxy-1,4-quinone). The modulated conductivity (σ≈2.53×10-5  S cm-1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m2 g-1 ) of the Cu3 (HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor.

6.
Angew Chem Int Ed Engl ; 59(17): 6652-6664, 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-31631497

RESUMO

There are two categories of coordination polymers (CPs): inorganic CPs (i-CPs) and organic ligand bridged CPs (o-CPs). Based on the successful crystal engineering of CPs, we here propose noncrystalline states and functionalities as a new research direction for CPs. Control over the liquid or glassy states in materials is essential to obtain specific properties and functions. Several studies suggest the feasibility of obtaining liquid/glassy states in o-CPs by design principles. The combination of metal ions and organic bridging ligands, together with the liquid/glass phase transformation, offer the possibility to transform o-CPs into ionic liquids and other ionic soft materials. Synchrotron measurements and computational approaches contribute to elucidating the structures and dynamics of the liquid/glassy states of o-CPs. This offers the opportunity to tune the porosity, conductivity, transparency, and other material properties. The unique energy landscape of liquid/glass o-CPs offers opportunities for properties and functions that are complementary to those of the crystalline state.

7.
Chemistry ; 26(10): 2148-2153, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-31755603

RESUMO

The enhancement of gas adsorption utilizing weak interactions in porous compounds is highly demanding for the design of energy-efficient storage materials. Here, we present a rational design for such an adsorption process by using synergistic functions between dynamic motion in a local module and weak but specific host-guest interactions, that is, halogen-bond (XB) interactions in metal-organic frameworks (MOFs). We designed a new porous coordination polymer (PCP), that is, Br-PCP, the pore surfaces of which are decorated with -CH2 Br groups and could be useful for interaction with CO2 molecules. In accordance with our anticipation, in-situ studies suggest that the adsorption step at approximately 54 kPa during CO2 adsorption is indeed facilitated by XB interactions with little change in the structural volume. This approach of integrating flexible XB modules in rigid PCPs is applicable for designing advanced gas storage systems.

8.
Angew Chem Int Ed Engl ; 58(52): 19034-19040, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31602745

RESUMO

The effect of organic ligands on the separation performance of Zr based metal-organic framework (Zr-MOF) membranes was investigated. A series of Zr-MOF membranes with different ligand chemistry and functionality were synthesized by an in situ solvothermal method and a coordination modulation technique. The thin supported MOF layers (ca. 1 µm) showed the crystallographic orientation and pore structure of original MOF structures. The MOF membranes show excellent selectivity towards hydrogen owing to the molecular sieving effect when the bulkier linkers were used. The molecular simulation confirmed that the constricted pore apertures of the Zr-MOFs which were formed by the additional benzene rings lead to the decrease in the diffusivity of larger penetrants while hydrogen was not remarkably affected. The gas mixture separation factors of the MOF membranes reached to H2 /CO2 =26, H2 /N2 =13, H2 /CH4 =11.

9.
Nat Commun ; 10(1): 4362, 2019 09 25.
Artigo em Inglês | MEDLINE | ID: mdl-31554816

RESUMO

Direct structural information of confined CO2 in a micropore is important for elucidating its specific binding or activation mechanism. However, weak gas-binding ability and/or poor sample crystallinity after guest exchange hindered the development of efficient materials for CO2 incorporation, activation and conversion. Here, we present a dynamic porous coordination polymer (PCP) material with local flexibility, in which the propeller-like ligands rotate to permit CO2 trapping. This process can be characterized by X-ray structural analysis. Owing to its high affinity towards CO2 and the confinement effect, the PCP exhibits high catalytic activity, rapid transformation dynamics, even high size selectivity to different substrates. Together with an excellent stability with turnover numbers (TON) of up to 39,000 per Zn1.5 cluster of catalyst after 10 cycles for CO2 cycloaddition to form value-added cyclic carbonates, these results demonstrate that such distinctive structure is responsible for visual CO2 capture and size-selective conversion.

10.
Chem Sci ; 10(24): 6193-6198, 2019 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-31360426

RESUMO

Control of the reactivity of hydride (H-) in crystal structures has been a challenge because of its strong electron-donating ability and reactivity with protic species. For metal borohydrides, the dehydrogenation activity and air stability are in a trade-off, and control of the reactivity of BH4 - has been demanded. For this purpose, we synthesize a series of BH4 --based coordination polymers/metal-organic frameworks. The reactivity of BH4 - in the structures is regulated by coordination geometry and neighboring ligands, and one of the compounds [Zn(BH4)2(dipyridylpropane)] exhibits both high dehydrogenation reactivity (1.4 wt% at 179 °C) and high air stability (50 RH% at 25 °C, 7 days). Single crystal X-ray diffraction analysis reveals that H δ+···H δ- dihydrogen interactions and close packing of hydrophobic ligands are the key for the reactivity and stability. The dehydrogenation mechanism is investigated by temperature-programmed desorption, in situ synchrotron PXRD and solid-state NMR.

11.
Chem Commun (Camb) ; 55(59): 8528-8531, 2019 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-31259321

RESUMO

We describe the preparation of the crystalline and glassy state of a coordination polymer displaying proton conduction and guest-accessible porosity. EXAFS and solid-state NMR analyses indicated that pyrophosphate and phosphate ions are the main proton transporters in the glass and that homogeneously distributed 5-chloro-1H-benzimidazole in the glass provides the porosity.

12.
Chem Commun (Camb) ; 55(38): 5455-5458, 2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-30997908

RESUMO

Crystal melting and glass formation of coordination polymers (CPs) and metal-organic frameworks (MOFs) are rare thermal events. To expand the library of melting CP/MOFs, we utilized anti-crystal engineering in ionic liquids to construct CPs. A combination of Cu+ and 4,4'-bipyridin-1-ium derivatives afforded four melting CPs showing stable liquid and glassy states.

13.
Chemistry ; 25(12): 3020-3031, 2019 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-30614084

RESUMO

Optimal control of gas adsorption properties in metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) remains a great challenge in the field of materials science. An efficient strategy to capture electron-acceptor-type gas molecules such as nitrogen monooxide (NO) is to use host-guest interactions by utilizing electron-donor-type MOFs/PCPs as host frameworks. Herein, we focus on a highly electron-donating chain compound by using the paddlewheel-type [Ru2 II,II ] complex [Ru2 (2,4,5-Me3 PhCO2 )4 ] (2,4,5-Me3 PhCO2 - =2,4,5-trimethylbenzoate) with the phenazine (phz) linker: [Ru2 (2,4,5-Me3 PhCO2 )4 (phz)] (1). Compound 1 exhibited a specific gated adsorption for NO under gas pressures greater than 60 kPa at 121 K, which finally resulted in approximately seven molar equivalents being taken up at 100 kPa followed by four molar equivalents remaining under vacuum at 121 K; its Rh isomorph (2) with weaker donation ability was inactive for NO. When the sample of 1⊃4 NO was heated to room temperature, the compound underwent a crystal-to-crystal phase transition to give [Ru2 (2,4,5-Me3 PhCO2 )4 (NO)2 ](phz) (1-NO), involving a post-synthetic nitrosylation on the [Ru2 ] unit, accompanied by an eventful site-exchange with phz. This drastic event, which is dependent on the NO pressure, temperature, and time, was coherently monitored by using several different in situ techniques, revealing that the stabilization of NO molecules in nanosized pores dynamically and stepwisely occurred with the support of strong electronic/magnetic host-guest interactions.

14.
Science ; 363(6425): 387-391, 2019 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-30679369

RESUMO

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.

15.
Nat Chem ; 11(2): 109-116, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30510215

RESUMO

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.

16.
J Am Chem Soc ; 141(3): 1227-1234, 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30576136

RESUMO

Design of molecular structures showing fast ion conductive/transport pathways in the solid state has been a significant challenge. The amorphous or glassy phase in organic polymers works well for fast ion conductivity because of their dynamic and random structure. However, the main issue with these polymers has been the difficulty in elucidating the mechanisms of ion conduction and thus low designability. Furthermore, the amorphous or glassy state of ion conductive polymers often confronts the problems of structural/mechanical stabilities. Covalent organic frameworks (COFs) are an emerging class of crystalline organic polymers with periodic structure and tunable functionality, which exhibit potential as a unique ion conductor/transporter. Here, we describe the use of a COF as a medium for all-solid-state Li+ conductivity. A bottom-up self-assembly approach was applied to covalently reticulate the flexible, bulky, and glassy poly(ethylene oxide) (PEO) moieties that can solvate Li+ for fast transport by their segmental motion in the rigid two-dimensional COF architectures. Temperature-dependent powder X-ray diffraction and thermogravimetric analysis showed that the periodic structures are intact even above 300 °C, and differential scanning calorimetry and solid-state NMR revealed that the accumulated PEO chains are highly dynamic and exhibit a glassy state. Li+ conductivity was found to depend on the dynamics and length of PEO chains in the crystalline states, and solid-state Li+ conductivity of 1.33 × 10-3 S cm-1 was achieved at 200 °C after LiTFSI doping. The high conductivity at the specified temperature remains intact for extended periods of time as a result of the structure's robustness. Furthermore, we demonstrated the first application of a COF electrolyte in an all-solid-state Li battery at 100 °C.

17.
Nat Commun ; 9(1): 5420, 2018 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-30575750

RESUMO

Gas-sensing materials are becoming increasingly important in our society, requiring high sensitivity to differentiate similar gases like N2 and O2. For the design of such materials, the driving force of electronic host-guest interaction or host-framework changes during the sorption process has commonly been considered necessary; however, this work demonstrates the use of the magnetic characteristics intrinsic to the guest molecules for distinguishing between diamagnetic N2 and CO2 gases from paramagnetic O2 gas. While the uptake of N2 and CO2 leads to an increase in TC through ferrimagnetic behavior, the uptake of O2 results in an O2 pressure-dependent continuous phase change from a ferrimagnet to an antiferromagnet, eventually leading to a novel ferrimagnet with aligned O2 spins following application of a magnetic field. This chameleonic material, the first with switchable magnetism that can discriminate between similarly sized N2 and O2 gases, provides wide scope for new gas-responsive porous magnets.

18.
Chem Sci ; 9(31): 6463-6469, 2018 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-30310576

RESUMO

Gate-opening gas sorption is known for metal-organic frameworks, and is associated with structural flexibility and advantageous properties for sensing and gas uptake. Here, we show that gate-opening is also possible for metal-organic polyhedra (MOPs), and depends on the molecular organisation in the lattice. Thanks to the solubility of MOPs, several interchangeable solvatomorphs of a lantern-type MOP were synthesised via treatment with different solvents. One phase obtained through use of methanol induced a gate-opening effect in the lattice in response to carbon dioxide uptake. The sorption process was thoroughly investigated with in situ powder X-ray diffraction and simultaneous adsorption experiments. Meanwhile, solution processing of this flexible phase using THF led to a permanently porous phase without a gate-opening effect. Furthermore, we find that we can change the metallic composition of the MOP, and yet retain flexibility. By showing that gate-opening can be switched on and off depending on the solvent of crystallisation, these findings have implications for the solution-based processing of MOPs.

19.
J Am Chem Soc ; 140(42): 13786-13792, 2018 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-30269483

RESUMO

We demonstrate a new de novo synthetic methodology to achieve high-temperature-stable compelled composite superhydrophobic porous coordination polymers (PCPs). These new PCPs were achieved based on coordination capabilities of first-row transition metal ions such as Co2+, Ni2+, and Zn2+. The obtained composite PCPs containing a [Zn2M2O]6+ (M = Co or Ni) bimetallic cluster core with open metal sites (OMSs) exhibited distinct isosteric heats of adsorption and surface areas due to the difference in their open metal Lewis acidic sites of solvent-free state. Additionally, these composite PCPs exhibit remarkable superhydrophobic properties with contact angles of 159.3° and 160.8° respectively for Zn-Co and Zn-Ni analogues. This superhydrophobic surface survives even at high temperature for longer time periods. As projected, these new composite PCPs exhibit better surface area and heats of adsorption compared to the PESD-1 (Zn) analogue due to a larger number of OMSs. Moreover, they display selective adsorption toward aromatic solvents such as benzene and toluene over aliphatic solvents such as cyclohexane due to corrugated and terminated aromatic hydrocarbon moieties toward the interactive surface. They also exhibit oil spill cleanup from the water surface in the powder form as well as pellet form up to 385 wt %. This study certainly offers a roadmap for designing and engineering new composite superhydrophobic porous materials for better water and thermal stability along with OMSs. This type of PCP exhibits a wide range of applications especially in catalysis, separation technology, and securing environmental problems such as oil spill cleanup in seawater.

20.
Acc Chem Res ; 51(10): 2437-2446, 2018 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-30252435

RESUMO

Metal-organic frameworks (MOFs) and porous coordination polymers (PCPs) have been well-recognized as emerging porous materials that afford highly tailorable and well-defined nanoporous structures with three-dimensional lattices. Because of their microporous nature, MOFs can accommodate small molecules in their lattice structure, thus discriminating them on the basis of their size and physical properties and enabling their separation even in the gas phase. Such characteristics of MOFs have attracted significant attention in recent years for diverse applications and have ignited a worldwide race toward their development in both academic and industrial fields. Most recently, new challenges in porous materials science demand processable liquid, melt, and amorphous forms of MOFs. This trend will provide a new fundamental class of microporous materials for further widespread applications in many fields. In particular, the application of flexible membranes for gas separation is expected as an efficient solution to tackle current energy-intensive issues. To date, amorphous MOFs have been prepared in a top-down approach by the introduction of disorder into the parent frameworks. However, this new paradigm is still in its infancy with respect to the rational design principles that need to be developed for any approach that may include bottom-up synthesis of porous soft materials. Herein we describe recent progress in bottom-up "modular" approaches for the synthesis of porous, processable MOF-based materials, wherein metal-organic cages (MOCs), alternatively called metal-organic polyhedra (MOPs), are used as "modular cavities" to build porous soft materials. The outer periphery of a MOP is decorated with polymeric and dendritic side chains to obtain a polymer-grafted MOP, imparting both solution and thermal processability to the MOP cages, which have an inherent nanocavity along with high tailorability analogous to MOFs. Well-ordered MOP assemblies can be designed to obtain phases ranging from crystals to liquid crystals, allowing the fabrication of flexible free-standing sheets with preservation of the long-range ordering of MOPs. Furthermore, future prospects of the modular design for porous soft materials are provided with the anticipation that the bottom-up design will combine porous materials and soft matter sciences, leading to the discovery and development of many unexplored new materials and devices such as MOF-based self-healing membranes possessing well-defined nanochannels. The macroscopic alignment of channels can be controlled by external factors, including electric and magnetic fields, external forces, and modified surfaces (templating and patterning), which are conventionally used for engineering of soft materials.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA