Observation of an Intermediate to H2 Binding in a Metal–organic Framework

Coordinatively-unsaturated metal sites within certain zeolites and metal–organic frameworks can strongly adsorb various molecules. While many classical examples involve electron-poor metal cations that interact with adsorbates largely through electrostatic interactions, unsaturated electron-rich metal centers housed within porous frameworks can often chemisorb guests amenable to redox activity or covalent bond formation. Despite the promise that materials bearing such sites hold in addressing myriad challenges in gas separations and storage, very few studies have directly interrogated mechanisms of chemisorption at open metal sites within porous frameworks. Here, we show that H2chemisorption at the trigonal pyramidal Cu+sites in the metal–organic framework CuI‑MFU-4l occurs via the intermediacy of a metastable physisorbed precursor species. In situpowder neutron diffraction experiments enable crystallographic characterization of this intermediate, the first time that this has been accomplished for any material. Support for a precursor intermediate is also afforded from temperature-programmed desorption and density functional theory calculations. The activation barrier separating the precursor species from the chemisorbed state is shown to correlate with a change in the Cu+coordination environment that enhances π-backbonding with H2. Ultimately, these findings demonstrate that adsorption at framework metal sites does not always follow a concerted pathway and underscore the importance of probing kinetics in the design of next-generation adsorbents.

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Selective capture of carbon dioxide from hydrocarbons using a metal-organic framework

Nature Communications ◽

10.1038/s41467-020-20489-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Omid T. Qazvini ◽

Ravichandar Babarao ◽

Shane G. Telfer

Keyword(s):

Carbon Dioxide ◽

Density Functional ◽

Metal Organic Framework ◽

Density Functional Theory Calculations ◽

Time Lags ◽

X Ray Crystallography ◽

Metal Organic ◽

Adsorption Of Co ◽

Short Time ◽

Organic Framework

AbstractEfficient and sustainable methods for carbon dioxide capture are highly sought after. Mature technologies involve chemical reactions that absorb CO2, but they have many drawbacks. Energy-efficient alternatives may be realised by porous physisorbents with void spaces that are complementary in size and electrostatic potential to molecular CO2. Here, we present a robust, recyclable and inexpensive adsorbent termed MUF-16. This metal-organic framework captures CO2 with a high affinity in its one-dimensional channels, as determined by adsorption isotherms, X-ray crystallography and density-functional theory calculations. Its low affinity for other competing gases delivers high selectivity for the adsorption of CO2 over methane, acetylene, ethylene, ethane, propylene and propane. For equimolar mixtures of CO2/CH4 and CO2/C2H2, the selectivity is 6690 and 510, respectively. Breakthrough gas separations under dynamic conditions benefit from short time lags in the elution of the weakly-adsorbed component to deliver high-purity hydrocarbon products, including pure methane and acetylene.

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Tuning the properties of metal–organic framework nodes as supports of single-site iridium catalysts: node modification by atomic layer deposition of aluminium

Faraday Discussions ◽

10.1039/c7fd00031f ◽

2017 ◽

Vol 201 ◽

pp. 195-206 ◽

Cited By ~ 20

Author(s):

Dong Yang ◽

Mohammad R. Momeni ◽

Hakan Demir ◽

Dale R. Pahls ◽

Martino Rimoldi ◽

...

Keyword(s):

Atomic Layer Deposition ◽

Density Functional ◽

Metal Organic Framework ◽

Density Functional Theory Calculations ◽

Atomic Layer ◽

Single Site ◽

Iridium Complexes ◽

Layer Deposition ◽

Metal Organic ◽

Organic Framework

The metal–organic framework NU-1000, with Zr6-oxo, hydroxo, and aqua nodes, was modified by incorporation of hydroxylated Al(iii) ions by ALD-like chemistry with [Al(CH3)2(iso-propoxide)]2 followed by steam (ALD = atomic layer deposition). Al ions were installed to the extent of approximately 7 per node. Single-site iridium diethylene complexes were anchored to the nodes of the modified and unmodified MOFs by reaction with Ir(C2H4)2(acac) (acac = acetylacetonate) and converted to Ir(CO)2 complexes by treatment with CO. Infrared spectra of these supported complexes show that incorporation of Al weakened the electron donor tendency of the MOF. Correspondingly, the catalytic activity of the initial supported iridium complexes for ethylene hydrogenation increased, as did the selectivity for ethylene dimerization. The results of density functional theory calculations with a simplified model of the nodes incorporating Al(iii) ions are in qualitative agreement with some catalyst performance data.

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Density-functional theory models of Fe(iv)O reactivity in metal–organic frameworks: self-interaction error, spin delocalisation and the role of hybrid exchange

Physical Chemistry Chemical Physics ◽

10.1039/d0cp01285h ◽

2020 ◽

Vol 22 (22) ◽

pp. 12821-12830

Author(s):

Fernan Saiz ◽

Leonardo Bernasconi

Keyword(s):

Density Functional Theory ◽

Oxidation Reaction ◽

Density Functional ◽

Metal Organic Framework ◽

Metal Organic Frameworks ◽

Density Functional Theory Calculations ◽

Functional Theory ◽

Metal Organic ◽

Organic Framework

We study the reactivity of Fe(iv)O moieties supported by a metal–organic framework (MOF-74) in the oxidation reaction of methane to methanol using all-electron, periodic density-functional theory calculations.

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Synthesis of copper metal organic framework based on Schiff base tricarboxylate ligand for highly selective and sensitive detection of 2,4,6-trinitrophenol in aqueous medium

10.21203/rs.3.rs-732172/v1 ◽

2021 ◽

Author(s):

Manpreet Kaur ◽

M. Yususf ◽

Ashok Kumar Malik

Keyword(s):

Schiff Base ◽

Aqueous Medium ◽

Electrostatic Interactions ◽

Density Functional ◽

Metal Organic Framework ◽

Copper Metal ◽

X Ray ◽

Metal Organic ◽

Functional Features ◽

Organic Framework

Abstract By using Schiff base tricarboxylate ligand 5-(4-carboxybenzylideneamino)isophthalic acid (H 3 CIP), a new imine functionalized copper metal organic framework (MOF) has been synthesized solvothermally. It was fully characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and elemental mapping techniques. The as-synthesized MOF has been utilized as fluorescent probe for detection of nitro aromatic explosives (NAEs). The results show that the copper MOF can be developed into highly selective and sensitive sensor for detection of TNP in the aqueous medium via the “turn-off” quenching response. The linear fitting of the Stern-Volmer plot for TNP offered large quenching constant of 1.07 × 10 4 M −1 for Cu-MOF indicating the high sensitivity of the sensing process. Outstanding sensitivity of prepared material towards TNP detection was further validated by the low detection limit of 80 ppb (0.35 µM). The detailed mechanistic studies for their mode of action and density functional theory (DFT) calculations reveals that photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) processes, as well as electrostatic interactions ( i.e. H-bonding) are the key factors for the turn-off response toward TNP by this fluorescent sensor. Thus, this new LMOF owing to their high water stability and remarkable functional features are potential candidates which can be developed into selective and sensitive TNP detection devices.

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Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding

10.26434/chemrxiv.10316681.v1 ◽

2019 ◽

Author(s):

Andrew Rosen ◽

M. Rasel Mian ◽

Timur Islamoglu ◽

Haoyuan Chen ◽

Omar Farha ◽

...

Keyword(s):

Density Functional ◽

Metal Organic Frameworks ◽

Redox Activity ◽

Screening Methods ◽

Bridging Ligands ◽

Metal Centers ◽

Computational Screening ◽

Open Metal Sites ◽

Metal Organic ◽

Unsaturated Metal Sites

Metal−organic frameworks (MOFs) with coordinatively unsaturated metal sites are appealing as adsorbent materials due to their tunable functionality and ability to selectively bind small molecules. Through the use of computational screening methods based on periodic density functional theory, we investigate O2 and N2 adsorption at the coordinatively unsaturated metal sites of several MOF families. A variety of design handles are identified that can be used to modify the redox activity of the metal centers, including changing the functionalization of the linkers (replacing oxido donors with sulfido donors), anion exchange of bridging ligands (considering μ-Br-, μ-Cl-, μ-F-, μ-SH-, or μ-OH- groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O2 affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O2. In contrast with O2 adsorption, N2 adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V2+ open metal sites. As one example from the screening study, we predict that exchanging the μ-Cl- ligands of M2Cl2(BBTA) (H2BBTA = 1H,5H-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH- groups would significantly enhance the strength of O2 adsorption at the open metal sites without a corresponding increase in the N2 affinity. Experimental investigation of Co2Cl2(BBTA) and Co2(OH)2(BBTA) confirms that the former exhibits only weak physisorption, whereas the latter is capable of chemisorbing O2 at room temperature. The chemisorption behavior is attributed to the greater electron-donating character of the μ-OH- ligands and the presence of H-bonding interactions between the μ-OH- bridging ligands and the O2 adsorbate.

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Density Functional Investigation of the Conversion of Furfural to Furfuryl Alcohol by Reaction with i-Propanol over UiO-66 Metal–Organic Framework

Inorganic Chemistry ◽

10.1021/acs.inorgchem.0c03764 ◽

2021 ◽

Author(s):

Jarinya Sittiwong ◽

Sininat Boonmark ◽

Watinee Nunthakitgoson ◽

Thana Maihom ◽

Chularat Wattanakit ◽

...

Keyword(s):

Furfuryl Alcohol ◽

Density Functional ◽

Metal Organic Framework ◽

Metal Organic ◽

Functional Investigation ◽

Organic Framework

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Exposing unsaturated Cu1-O2 sites in nanoscale Cu-MOF for efficient electrocatalytic hydrogen evolution

Science Advances ◽

10.1126/sciadv.abg2580 ◽

2021 ◽

Vol 7 (18) ◽

pp. eabg2580

Author(s):

Weiren Cheng ◽

Huabin Zhang ◽

Deyan Luan ◽

Xiong Wen (David) Lou

Keyword(s):

Hydrogen Evolution ◽

Density Functional ◽

Metal Organic Framework ◽

Density Functional Theory Calculations ◽

Active Centers ◽

Functional Theory ◽

Hollow Nanostructure ◽

Metal Organic ◽

X Ray Absorption ◽

A Current

Conductive metal-organic framework (MOF) materials have been recently considered as effective electrocatalysts. However, they usually suffer from two major drawbacks, poor electrochemical stability and low electrocatalytic activity in bulk form. Here, we have developed a rational strategy to fabricate a promising electrocatalyst composed of a nanoscale conductive copper-based MOF (Cu-MOF) layer fully supported over synergetic iron hydr(oxy)oxide [Fe(OH)x] nanoboxes. Owing to the highly exposed active centers, enhanced charge transfer, and robust hollow nanostructure, the obtained Fe(OH)x@Cu-MOF nanoboxes exhibit superior activity and stability for the electrocatalytic hydrogen evolution reaction (HER). Specifically, it needs an overpotential of 112 mV to reach a current density of 10 mA cm−2 with a small Tafel slope of 76 mV dec−1. X-ray absorption fine structure spectroscopy combined with density functional theory calculations unravels that the highly exposed coordinatively unsaturated Cu1-O2 centers could effectively accelerate the formation of key *H intermediates toward fast HER kinetics.

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Elucidating the Drug Release from Metal-Organic Framework Nanocomposites via in Situ Synchrotron Microspectroscopy and Theoretical Modelling

10.26434/chemrxiv.9975389 ◽

2019 ◽

Author(s):

Barbara Souza ◽

Lorenzo Dona ◽

Kirill Titov ◽

Paolo Bruzzese ◽

Zhixin Zeng ◽

...

Keyword(s):

Drug Delivery ◽

Drug Release ◽

Density Functional ◽

Metal Organic Framework ◽

Density Functional Theory Calculations ◽

Theoretical Modelling ◽

Time Resolved ◽

Drug Molecules ◽

Metal Organic

Nanocomposites comprising metal-organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the release of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.

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Mechanochemical Synthesis of a Mercury(II) Metal-Organic Framework Reveals a Two-Dimensional Polymorph Stabilized by Weak Interactions

10.26434/chemrxiv.9725303.v1 ◽

2019 ◽

Author(s):

Isaiah R. Speight ◽

Igor Huskić ◽

Mihails Arhangelskis ◽

Hatem M. Titi ◽

Robin Stein ◽

...

Keyword(s):

Density Functional ◽

Weak Interactions ◽

Metal Organic Framework ◽

Three Dimensional ◽

Density Functional Theory Calculations ◽

Dimensional Structure ◽

Reaction Monitoring ◽

Two Dimensional ◽

Functional Theory ◽

Metal Organic

Solid-state mechanochemistry revealed a novel polymorph of the mercury(II) imidazolate framework, based on square-grid (sql) topology layers. Reaction monitoring and periodic density functional theory calculations show that the sql-structure is of higher stability than the previously reported three-dimensional structure, with the unexpected stabilization of a lower dimensionality structure explained by contributions of weak interactions, which include short C-H···Hg contacts.

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