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1.
Chem Rev ; 2020 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-32692163

RESUMO

Open framework materials (OFM) constitute a large and growing class of nanoporous crystalline structures that is attracting considerable attention for electronic device applications. This review summarizes the most recent reports concerning electronic devices enabled by either of the two primary categories of OFM, metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs). Devices in which the OFM plays an active role (as opposed to acting only as a selective sorbent or filter) are the principal focus, with examples cited that include field-effect transistors, capacitors, memristors, and a wide variety of sensing architectures. As a brief tutorial, we also provide a concise summary of various methods of depositing or growing OFM on surfaces, as these are of crucial importance to the deployment of electronic OFM. Finally, we offer our perspective concerning future research directions, particularly regarding what in our view are the biggest challenges remaining to be addressed. On the basis of the literature discussed here, we conclude that OFM constitute a unique class of electronic materials with characteristics and advantages that are distinct from either conventional inorganic semiconductors or organic conductors. This suggests a bright future for these materials in applications such as edge computing, resistive switching, and mechanically flexible sensing and electronics.

2.
J Phys Chem Lett ; : 5856-5862, 2020 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-32615766

RESUMO

Flexible metal-organic frameworks (MOFs) exhibit a variety of phenomena attractive for basic and applied science. DUT-49(Cu) is one of the remarkable representatives of such MOFs, where phase transitions are coupled to pressure amplification and "negative gas adsorption". In this work we report important insights into structural transitions of DUT-49(Cu) upon physi- and chemisorption of gases and volatile liquids obtained by in situ electron paramagnetic resonance (EPR) spectroscopy. In this method, phase transitions are detected via the zero-field splitting in dimeric copper(II) units. First, a new approach was validated upon physisorption of n-butane. Then, using diethyl ether, we for the first time demonstrated that chemisorption can also trigger phase transition in DUT-49(Cu). On the basis of the EPR results, the transition appears completely reversible. The developed EPR-based approach can also be extended to other flexible MOFs containing paramagnetic metal paddlewheels, where high sensitivity and spectral resolution allow in situ studies of stimuli-induced structural variability.

3.
Inorg Chem ; 2020 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-32663400

RESUMO

Four new layered flexible metal-organic frameworks (MOFs) containing a diacylhydrazone moiety, namely, guest-filled [Zn2(iso)2(tdih)2]n (1), [Zn2(NH2iso)2(tdih)2]n (2), [Cd2(iso)2(tdih)2]n (3) and [Cd2(NH2iso)2(tdih)2]n (4) were synthesized using terephthalaldehyde di-isonicotinoylhydrazone (tdih) as a linear ditopic linker as well as isophtalate (iso) or 5-aminoisophthalate (NH2iso) as angular colinkers. The MOFs with hexacoordinated cadmium centers feature two-dimensional pore systems as compared to the MOFs with pentacoordinated zinc centers showing either zero-dimensional or mixed zero-/one-dimensional voids, as evidenced by single-crystal X-ray diffraction. In contrast to the frameworks based on isophtalates which do not show any significant gas uptakes, introduction of amino-substituted linker enables CO2 adsorption. Gently activated aminoisophthalate-based frameworks, that is, guest-exchanged in methanol and heated to 100 °C, show reversible gated CO2 adsorptions at 195 K, whereas the increase of activation temperature to 150 °C or more leads to one-step isotherms and lower adsorption capacities. X-ray diffraction and IR spectroscopy reveal significant structural differences in interlayer hydrogen bonding upon activation of materials at higher temperatures. The work emphasizes the role of hydrogen bonds in crystal engineering of layered materials and the importance of activation conditions in such systems.

4.
Chem Commun (Camb) ; 56(59): 8269-8272, 2020 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-32568349

RESUMO

Experimental in situ observations of phase coexistence in switchable metal-organic frameworks are reported to provide a fundamental understanding of dynamic adsorbents that can change their pore structure in response to external stimuli. A prototypical flexible pillared layer framework DUT-8(Ni) (DUT = Dresden University of Technology) was studied under hydrostatic pressure by in situ Raman spectroscopy on single crystals. The closing transition of the open pore phase (op) containing DMF in the pores in silicon oil as a pressure transmitting fluid, as well as the closed pore phase (cp) to op transition under pressure in methanol, were studied. Phase coexistences during both transitions were observed.

5.
Chem Commun (Camb) ; 2020 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-32497159

RESUMO

We evaluate experimentally the force exerted by flexible metal-organic frameworks through expansion for a representative model system, namely MIL-53(Al). The results obtained are compared with data collected from intrusion experiments while molecular simulations are performed to shed light on the re-opening of the guest-loaded structure. The critical impact of the transition stimulating medium on the magnitude of the expansion force is demonstrated.

6.
Artigo em Inglês | MEDLINE | ID: mdl-32400958

RESUMO

The development of ultrastable carbon materials for potassium storage poses key limitations caused by the huge volume variation and sluggish kinetics. Nitrogen-enriched porous carbons have recently emerged as promising candidates for this application; however, rational control over nitrogen doping is needed to further suppress the long-term capacity fading. Here we propose a strategy based on pyrolysis-etching of a pyridine-coordinated polymer for deliberate manipulation of edge-nitrogen doping and specific spatial distribution in amorphous high-surface-area carbons; the obtained material shows an edge-nitrogen content of up to 9.34 at %, richer N distribution inside the material, and high surface area of 616 m2 g-1 under a cost-effective low-temperature carbonization. The optimized carbon delivers unprecedented K-storage stability over 6000 cycles with negligible capacity decay (252 mA h g-1 after 4 months at 1 A g-1 ), rarely reported for potassium storage.

8.
ChemSusChem ; 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32243702

RESUMO

The synthesis of porous electrode materials is often linked with the generation of waste that results from extensive purification steps and low mass yield. In contrast to porous carbons, covalent triazine frameworks (CTFs) display modular properties on a molecular basis through appropriate choice of the monomer. Herein, the synthesis of a new pyridine-based CTF material is showcased. The porosity and nitrogen-doping are tuned by a careful choice of the reaction temperature. An in-depth structural characterization by using Ar physisorption, X-ray photoelectron spectroscopy, and Raman spectroscopy was conducted to give a rational explanation of the material properties. Without any purification, the samples were applied as symmetrical supercapacitors and showed a specific capacitance of 141 F g-1 . Residual ZnCl2 , which acted formerly as the porogen, was used directly as the electrolyte salt. Upon the addition of water, ZnCl2 was dissolved to form the aqueous electrolyte in situ. Thereby, extensive and time-consuming washing steps could be circumvented.

9.
Nat Commun ; 11(1): 1590, 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-32221287

RESUMO

Amongst various porous materials, noble metal aerogels attract wide attention due to their concurrently featured catalytic properties and large surface areas. However, insufficient understanding and investigation of key factors (e.g. reductants and ligands) in the fabrication process limits on-target design, impeding material diversity and available applications. Herein, unveiling multiple roles of reductants, we develop an efficient method, i.e. the excessive-reductant-directed gelation strategy. It enables to integrate ligand chemistry for creating gold aerogels with a record-high specific surface area (59.8 m2 g-1), and to expand the composition to all common noble metals. Moreover, we demonstrate impressive electrocatalytic performance of these aerogels for the ethanol oxidation and oxygen evolution reaction, and discover an unconventional organic-ligand-enhancing effect. The present work not only enriches the composition and structural diversity of noble metal aerogels, but also opens up new dimensions for devising efficient electrocatalysts for broad material systems.

10.
Chem Soc Rev ; 49(5): 1414-1448, 2020 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-32039429

RESUMO

Oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are three key reactions for the development of green and sustainable energy systems. Efficient electrocatalysts for these reactions are highly desired to lower their overpotentials and promote practical applications of related energy devices. Metal-organic frameworks (MOFs) have recently emerged as precursors to fabricate carbon-based electrocatalysts with high electrical conductivity and uniformly distributed active sites. In this review, the current progress of MOF-derived carbon-based materials for ORR/OER/HER electrocatalysis is presented. Materials design strategies of MOF-derived carbon-based materials are firstly summarized to show the rich possibilities of the morphology and composition of MOF-derived carbon-based materials. A wide range of applications based on these materials for ORR, OER, HER and multifunctional electrocatalysis are discussed, with an emphasis on the required features of MOF-derived carbon-based materials for the electrocatalysis of corresponding reactions. Finally, perspectives on the development of MOF-derived carbon-based materials for ORR, OER and HER electrocatalysis are provided.

11.
Dalton Trans ; 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32073068

RESUMO

New 3D Ni and Co redox-active metal-organic frameworks based on ferrocenyl diphosphinate and 4,4'-bipyridine ligands have been synthesized, characterized by single crystal X-ray diffraction and spectroscopic techniques and explored as stable electrocatalysts capable of meeting two important parameters: the overpotential and Tafel slope (TS) in the hydrogen evolution reaction (HER). The electrochemical studies suggest that the reaction kinetics of a Ni-MOF (1) catalyst is more favorable than that of a Co-MOF (2) catalyst. Particularly, Ni-MOF exhibits better HER performance with an overpotential of 350 mV at a current density of 10 mA cm-2, a small TS of 60 mV dec-1 and superior long-term durability (of up to 10 000 cycles), ranking it among the most active non-noble metal-based molecular electrocatalysts. The introduction of a 4,4'-bpy linker in 2 significantly changes the catalytic properties in an organic or aqueous environment compared to 1D cobalt polymers based on ferrocenyl diphosphinate. For Co-MOF 2, there is a significant decrease in the overvoltage by ∼440 mV in comparison with the 1D Co polymer in an organic medium and by 50 mV in an aqueous medium. The TS changes from 120 to 65 mV dec-1 when moving from 1D CofcdHp to a 3D structure of 2. Thus, a 4,4'-bpy linker reduces the overvoltage and gives more favorable HER kinetics (lower TS). These results provide important guidelines for the rational design of non-precious metal electrocatalysts.

12.
Sci Adv ; 6(1): eaay2757, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31922008

RESUMO

Lithium-sulfur batteries can displace lithium-ion by delivering higher specific energy. Presently, however, the superior energy performance fades rapidly when the sulfur electrode is loaded to the required levels-5 to 10 mg cm-2- due to substantial volume change of lithiation/delithiation and the resultant stresses. Inspired by the classical approaches in particle agglomeration theories, we found an approach that places minimum amounts of a high-modulus binder between neighboring particles, leaving increased space for material expansion and ion diffusion. These expansion-tolerant electrodes with loadings up to 15 mg cm-2 yield high gravimetric (>1200 mA·hour g-1) and areal (19 mA·hour cm-2) capacities. The cells are stable for more than 200 cycles, unprecedented in such thick cathodes, with Coulombic efficiency above 99%.

13.
Artigo em Inglês | MEDLINE | ID: mdl-31917504

RESUMO

Functional materials that respond to chemical or physical stimuli through reversible structural transformations are highly desirable for the integration into devices. Now, a new stable and flexible eightfold interpenetrated three-dimensional (3D) metal-organic framework (MOF) is reported, [Zn(oba)(pip)]n (JUK-8) based on 4,4'-oxybis(benzenedicarboxylate) (oba) and 4-pyridyl functionalized benzene-1,3-dicarbohydrazide (pip) linkers, featuring distinct switchability in response to guest molecules (H2 O and CO2 ) or temperature. Single-crystal X-ray diffraction (SC-XRD), combined with density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations, reveal a unique breathing mechanism involving collective motions of eight mixed-linker diamondoid subnetworks with only minor displacements between them. The pronounced stepwise volume change of JUK-8 during water adsorption is used to construct an electron conducting composite film for resistive humidity sensing.

14.
Artigo em Inglês | MEDLINE | ID: mdl-31989749

RESUMO

Porphyrins and porphyrin derivatives have been widely explored for various applications owing to their excellent photophysical and electrochemical properties. However, inherent shortcomings, such as the instability and self-quenching in physiological conditions, limit their biomedical applications. In recent years, metal-organic frameworks (MOFs), as a new type of hybrid porous coordination polymers assembled from metal ions/secondary building units (SBUs) and organic linkers, have gained increasing attention. The construction of porphyrin-based MOFs by introducing porphyrin molecules into MOFs or using porphyrins as organic linkers to form MOFs can integrate the unique features of porphyrins and MOFs as well as overcome the limitations of porphyrins, facilitating their biomedical applications. This review article summarizes important synthesis strategies for porphyrin-based MOFs including porphyrin@MOFs, porphyrinic MOFs and composite porphyrinic MOFs, and highlights recent achievements and progress in the field of porphyrin-based MOFs for biomedical applications in tumor therapy and biosensing. Finally, the challenges and prospects of this class of emerging materials for biomedical applications are discussed.

15.
Inorg Chem ; 59(1): 350-359, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31820946

RESUMO

In situ formation of imine-based organic linkers facilitates the formation of metal-organic frameworks (MOFs), in particular if linker solubility hampers the direct synthesis. The reaction of ZrCl4 with 4-formylbenzoic acid or 4-formyl-3-hydroxybenzoic acid as the aldehyde source and 4-aminobenzoic acid as the amine source is shown to produce zirconium MOFs isoreticular to UiO-66 (PCN-161 and a novel DUT-133, [Zr6O4(OH)4(C15H9NO5)6], respectively). A similar reaction with p-phenylenediamine as the amine-containing building block gave 2-fold interpenetrated framework (PCN-164). Detailed characterization, including single crystal and powder X-ray diffraction, water stability tests, thermal stability, and in situ 1H and 13C NMR were performed to elucidate the formation mechanism of zirconium MOFs containing imine-based linkers. The resulting zirconium MOFs were evaluated as potential materials for CO2 capture and as ethylene oligomerization catalysts with anchored nickel as the active species.

16.
ACS Appl Mater Interfaces ; 11(44): 41188-41195, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31599563

RESUMO

Sluggish reaction kinetics induced by the poor solid-state ion diffusion and low electrical conductivity of electrode materials are currently in conflict with increasing fast-charge needs for sodium-ion batteries (SIBs) based on conversion mechanism. Herein, mesoporous, conductive, thin-wall three-dimensional (3D) skeletons of molybdenum nitride (meso-Mo2N) were established and employed as anodes to facilitate the rate performance of SIBs. Mesoporous channels (∼9.3 nm) with very thin walls (<8 nm) and conductive networks in meso-Mo2N enable the rapid Na+ infiltrability/diffusion and fast electron migration, respectively. The facilitated ion diffusion/transfer ability is corroborated by cyclic voltammetry tests and galvanostatic intermittent titration technique with a higher Na+ diffusion coefficient and a larger Na+ diffusion-dominated capacity. Consequently, meso-Mo2N exhibits a superior rate capability and a steady specific capacity of 158 mAh g-1 at 1 A g-1 after 1000 cycles for SIBs, surpassing the nonporous Mo2N and even the previously reported Mo2N. Furthermore, the proof of concept can be also extended to enhanced Li storage. Such a mesostructured design with 3D mesoporous, conductive thin walls of electrodes is a promising strategy for achieving fast-charging and high-performance Na/Li storage.

17.
Chem Asian J ; 14(20): 3450-3451, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31613062

RESUMO

What a collection! This special issue contains latest works on MOFs and MOF-based materials from various research groups from across the world.

18.
Beilstein J Nanotechnol ; 10: 1737-1744, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31501745

RESUMO

In this contribution we analyze the influence of adsorption cycling, crystal size, and temperature on the switching behavior of the flexible Zr-based metal-organic framework DUT-98. We observe a shift in the gate-opening pressure upon cycling of adsorption experiments for micrometer-sized crystals and assign this to a fragmentation of the crystals. In a series of samples, the average crystal size of DUT-98 crystals was varied from 120 µm to 50 nm and the obtained solids were characterized by X-ray diffraction, infrared spectroscopy, as well as scanning and transmission electron microscopy. We analyzed the adsorption behavior by nitrogen and water adsorption at 77 K and 298 K, respectively, and show that adsorption-induced flexibility is only observed for micrometer-sized crystals. Nanometer-sized crystals were found to exhibit reversible type I adsorption behavior upon adsorption of nitrogen and exhibit a crystal-size-dependent steep water uptake of up to 20 mmol g-1 at 0.5 p/p 0 with potential for water harvesting and heat pump applications. We furthermore investigate the temperature-induced structural transition by in situ powder X-ray diffraction. At temperatures beyond 110 °C, the open-pore state of the nanometer-sized DUT-98 crystals is found to irreversibly transform to a closed-pore state. The connection of crystal fragmentation upon adsorption cycling and the crystal size dependence of the adsorption-induced flexibility is an important finding for evaluation of these materials in future adsorption-based applications. This work thus extends the limited amount of studies on crystal size effects in flexible MOFs and hopefully motivates further investigations in this field.

19.
Nat Commun ; 10(1): 3632, 2019 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-31406113

RESUMO

Switchable metal-organic frameworks (MOFs) have been proposed for various energy-related storage and separation applications, but the mechanistic understanding of adsorption-induced switching transitions is still at an early stage. Here we report critical design criteria for negative gas adsorption (NGA), a counterintuitive feature of pressure amplifying materials, hitherto uniquely observed in a highly porous framework compound (DUT-49). These criteria are derived by analysing the physical effects of micromechanics, pore size, interpenetration, adsorption enthalpies, and the pore filling mechanism using advanced in situ X-ray and neutron diffraction, NMR spectroscopy, and calorimetric techniques parallelised to adsorption for a series of six isoreticular networks. Aided by computational modelling, we identify DUT-50 as a new pressure amplifying material featuring distinct NGA transitions upon methane and argon adsorption. In situ neutron diffraction analysis of the methane (CD4) adsorption sites at 111 K supported by grand canonical Monte Carlo simulations reveals a sudden population of the largest mesopore to be the critical filling step initiating structural contraction and NGA. In contrast, interpenetration leads to framework stiffening and specific pore volume reduction, both factors effectively suppressing NGA transitions.

20.
Nat Commun ; 10(1): 3260, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31332187

RESUMO

The realization of ferromagnetism in semiconductors is an attractive avenue for the development of spintronic applications. Here, we report a semiconducting layered metal-organic framework (MOF), namely K3Fe2[(2,3,9,10,16,17,23,24-octahydroxy phthalocyaninato)Fe] (K3Fe2[PcFe-O8]) with spontaneous magnetization. This layered MOF features in-plane full π-d conjugation and exhibits semiconducting behavior with a room temperature carrier mobility of 15 ± 2 cm2 V-1 s-1 as determined by time-resolved Terahertz spectroscopy. Magnetization experiments and 57Fe Mössbauer spectroscopy demonstrate the presence of long-range magnetic correlations in K3Fe2[PcFe-O8] arising from the magnetic coupling between iron centers via delocalized π electrons. The sample exhibits superparamagnetic features due to a distribution of crystal size and possesses magnetic hysteresis up to 350 K. Our work sets the stage for the development of spintronic materials exploiting magnetic MOF semiconductors.

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