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

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

<p>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 O<sub>2</sub> and N<sub>2</sub> 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<sup>-</sup>, μ-Cl<sup>-</sup>, μ-F<sup>-</sup>, μ-SH<sup>-</sup>, or μ-OH<sup>-</sup> groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O<sub>2</sub> affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O<sub>2</sub>. In contrast with O<sub>2</sub> adsorption, N<sub>2</sub> adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V<sup>2+</sup> open metal sites. As one example from the screening study, we predict that exchanging the μ-Cl<sup>-</sup> ligands of M<sub>2</sub>Cl<sub>2</sub>(BBTA) (H<sub>2</sub>BBTA = 1<i>H</i>,5<i>H</i>-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH<sup>-</sup> groups would significantly enhance the strength of O<sub>2</sub> adsorption at the open metal sites without a corresponding increase in the N<sub>2</sub> affinity. Experimental investigation of Co<sub>2</sub>Cl<sub>2</sub>(BBTA) and Co<sub>2</sub>(OH)<sub>2</sub>(BBTA) confirms that the former exhibits only weak physisorption, whereas the latter is capable of chemisorbing O<sub>2</sub> at room temperature. The chemisorption behavior is attributed to the greater electron-donating character of the μ-OH<sup>-</sup><sub> </sub>ligands and the presence of H-bonding interactions between the μ-OH<sup>-</sup> bridging ligands and the O<sub>2</sub> adsorbate.</p>

scholarly journals Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding: Design Rules and Ambient Temperature O2 Chemisorption in a Cobalt−Triazolate Framework

2020 ◽  
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

<p>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 O<sub>2</sub> and N<sub>2</sub> 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<sup>-</sup>, μ-Cl<sup>-</sup>, μ-F<sup>-</sup>, μ-SH<sup>-</sup>, or μ-OH<sup>-</sup> groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O<sub>2</sub> affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O<sub>2</sub>. In contrast with O<sub>2</sub> adsorption, N<sub>2</sub> adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V<sup>2+</sup> open metal sites. As one example from the screening study, we predicted that exchanging the μ-Cl<sup>-</sup> ligands of M<sub>2</sub>Cl<sub>2</sub>(BBTA) (H<sub>2</sub>BBTA = 1<i>H</i>,5<i>H</i>-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH<sup>-</sup> groups would significantly enhance the strength of O<sub>2</sub> adsorption at the open metal sites without a corresponding increase in the N<sub>2</sub> affinity. Experimental investigation of Co<sub>2</sub>Cl<sub>2</sub>(BBTA) and Co<sub>2</sub>(OH)<sub>2</sub>(BBTA) confirms that the former exhibits weak physisorption of both N<sub>2</sub> and O<sub>2</sub>, whereas the latter is capable of chemisorbing O<sub>2</sub> at room temperature in a highly selective manner. The O<sub>2</sub> chemisorption behavior is attributed to the greater electron-donating character of the μ-OH<sup>-</sup><sub> </sub>ligands and the presence of H-bonding interactions between the μ-OH<sup>-</sup> bridging ligands and the reduced O<sub>2</sub> adsorbate.<br></p>

scholarly journals Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding: Design Rules and Ambient Temperature O2 Chemisorption in a Cobalt−Triazolate Framework

2020 ◽  
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

<p>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 O<sub>2</sub> and N<sub>2</sub> 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<sup>-</sup>, μ-Cl<sup>-</sup>, μ-F<sup>-</sup>, μ-SH<sup>-</sup>, or μ-OH<sup>-</sup> groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O<sub>2</sub> affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O<sub>2</sub>. In contrast with O<sub>2</sub> adsorption, N<sub>2</sub> adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V<sup>2+</sup> open metal sites. As one example from the screening study, we predicted that exchanging the μ-Cl<sup>-</sup> ligands of M<sub>2</sub>Cl<sub>2</sub>(BBTA) (H<sub>2</sub>BBTA = 1<i>H</i>,5<i>H</i>-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH<sup>-</sup> groups would significantly enhance the strength of O<sub>2</sub> adsorption at the open metal sites without a corresponding increase in the N<sub>2</sub> affinity. Experimental investigation of Co<sub>2</sub>Cl<sub>2</sub>(BBTA) and Co<sub>2</sub>(OH)<sub>2</sub>(BBTA) confirms that the former exhibits weak physisorption of both N<sub>2</sub> and O<sub>2</sub>, whereas the latter is capable of chemisorbing O<sub>2</sub> at room temperature in a highly selective manner. The O<sub>2</sub> chemisorption behavior is attributed to the greater electron-donating character of the μ-OH<sup>-</sup><sub> </sub>ligands and the presence of H-bonding interactions between the μ-OH<sup>-</sup> bridging ligands and the reduced O<sub>2</sub> adsorbate.<br></p>

scholarly journals Screening for high-spin metal organic frameworks (MOFs): density functional theory study on DUT-8(M1,M2) (with Mi = V,…,Cu)

2016 ◽  
Vol 18 (11) ◽  
pp. 8075-8080 ◽  
Author(s):  
Sebastian Schwalbe ◽  
Kai Trepte ◽  
Gotthard Seifert ◽  
Jens Kortus
Keyword(s):  
Density Functional Theory ◽  
High Spin ◽  
First Principles ◽  
Density Functional ◽  
Metal Organic Framework ◽  
Metal Organic Frameworks ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Metal Centers ◽  
Metal Organic

We present a first principles study of low-spin (LS)/high-spin (HS) screening for 3d metal centers in the metal organic framework (MOF) DUT-8(Ni).

scholarly journals Thermodynamic Separation of 1-Butene from 2-Butene in Metal–Organic Frameworks with Open Metal Sites

2019 ◽  
Author(s):  
Brandon Barnett ◽  
Surya Parker ◽  
Maria V. Paley ◽  
Miguel I. Gonzalez ◽  
Naomi Biggins ◽  
...  
Keyword(s):  
Metal Organic Frameworks ◽  
Industrial Process ◽  
Cost Effective ◽  
Oil Refining ◽  
Batch Adsorption ◽  
Metal Centers ◽  
Academic Effort ◽  
Liquid Phases ◽  
Open Metal Sites ◽  
Metal Organic

Most C<sub>4</sub> hydrocarbons are obtained as byproducts of ethylene production or oil refining, and complex and energy-intensive separation schemes are required for their isolation. Substantial industrial and academic effort has been expended to develop more cost-effective adsorbent- or membrane-based approaches to purify commodity chemicals such as 1,3-butadiene, isobutene, and 1-butene, but the very similar physical properties of these C<sub>4</sub> hydrocarbons makes this a challenging task. Here, we examine the adsorption behavior of 1-butene, <i>cis</i>-2-butene and <i>trans</i>-2-butene in the metal–organic frameworks M<sub>2</sub>(dobdc) (M = Mn, Fe, Co, Ni; dobdc<sup>2</sup><sup>−</sup> = 2,5-dioxidobenzene-1,4-dicarboxylate) and M<sub>2</sub>(<i>m</i>-dobdc) (<i>m</i>-dobdc<sup>4</sup><sup>−</sup> = 4,6-dioxido-1,3-benzenedicarboxylate), which all contain a high density of coordinatively-unsaturated M<sup>2+</sup> sites. We find that both Co<sub>2</sub>(<i>m</i>-dobdc) and Ni<sub>2</sub>(<i>m</i>-dobdc) are able to separate 1-butene from the 2-butene isomers, a critical industrial process that relies largely on energetically demanding cryogenic distillation. The origin of 1-butene selectivity is traced to the high charge density retained by the M<sup>2+</sup> metal centers exposed within the M<sub>2</sub>(<i>m</i>-dobdc) structures, which results in a reversal of the <i>cis</i>-2-butene selectivity typically observed at framework open metal sites. Selectivity for 1-butene adsorption under multicomponent conditions is demonstrated for Ni<sub>2</sub>(<i>m</i>-dobdc) in both the gaseous and liquid phases via breakthrough and batch adsorption experiments.

DFT studies on storage and adsorption capacities of gases on MOFs

2018 ◽  
Vol 3 (8) ◽  
Author(s):  
Archa Gulati ◽  
Rita Kakkar
Keyword(s):  
Metal Ions ◽  
Density Functional ◽  
High Surface ◽  
Bridging Ligands ◽  
Crystalline Materials ◽  
Surface Areas ◽  
The Density Functional Theory ◽  
Open Metal Sites ◽  
Metal Organic

Abstract Metal-organic frameworks (MOFs) are highly porous crystalline materials, consisting of metal ions linked together with organic bridging ligands, exhibiting high surface areas. Lately, they have been utilized for gas sorption, storage, sensing, drug delivery, etc. The chemistry of MOFs is expanding with an extraordinary speed, constituting both theoretical and experimental research, and MOFs have proved to be promising candidates so far. In this work, we have reviewed the density functional theory studies of MOFs in the adsorption and separation of the greenhouse gas, CO2, as well as the storage efficiencies for fuel gases like H2, CH4 and C2H2. The role of organic ligands, doping with other metal ions and functional groups, open metal sites and hybrid MOFs have been reviewed in brief.

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

2020 ◽  
Author(s):  
Brandon Barnett ◽  
hayden evans ◽  
Gregory M. Su ◽  
Henry Z. H. Jiang ◽  
Romit Chakraborty ◽  
...  
Keyword(s):  
Electrostatic Interactions ◽  
Density Functional ◽  
Activation Barrier ◽  
Metal Organic Framework ◽  
Covalent Bond ◽  
Density Functional Theory Calculations ◽  
Redox Activity ◽  
Metal Centers ◽  
Metal Organic ◽  
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 H<sub>2</sub>chemisorption at the trigonal pyramidal Cu<sup>+</sup>sites in the metal–organic framework Cu<sup>I</sup>‑MFU-4<i>l </i>occurs via the intermediacy of a metastable physisorbed precursor species. <i>In situ</i>powder 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<sup>+</sup>coordination environment that enhances π-backbonding with H<sub>2</sub>. 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<b>.</b>

scholarly journals Thermodynamic Separation of 1-Butene from 2-Butene in Metal–Organic Frameworks with Open Metal Sites

2019 ◽  
Author(s):  
Brandon Barnett ◽  
Surya Parker ◽  
Maria V. Paley ◽  
Miguel I. Gonzalez ◽  
Naomi Biggins ◽  
...  
Keyword(s):  
Metal Organic Frameworks ◽  
Industrial Process ◽  
Cost Effective ◽  
Oil Refining ◽  
Batch Adsorption ◽  
Metal Centers ◽  
Academic Effort ◽  
Liquid Phases ◽  
Open Metal Sites ◽  
Metal Organic

Most C<sub>4</sub> hydrocarbons are obtained as byproducts of ethylene production or oil refining, and complex and energy-intensive separation schemes are required for their isolation. Substantial industrial and academic effort has been expended to develop more cost-effective adsorbent- or membrane-based approaches to purify commodity chemicals such as 1,3-butadiene, isobutene, and 1-butene, but the very similar physical properties of these C<sub>4</sub> hydrocarbons makes this a challenging task. Here, we examine the adsorption behavior of 1-butene, <i>cis</i>-2-butene and <i>trans</i>-2-butene in the metal–organic frameworks M<sub>2</sub>(dobdc) (M = Mn, Fe, Co, Ni; dobdc<sup>2</sup><sup>−</sup> = 2,5-dioxidobenzene-1,4-dicarboxylate) and M<sub>2</sub>(<i>m</i>-dobdc) (<i>m</i>-dobdc<sup>4</sup><sup>−</sup> = 4,6-dioxido-1,3-benzenedicarboxylate), which all contain a high density of coordinatively-unsaturated M<sup>2+</sup> sites. We find that both Co<sub>2</sub>(<i>m</i>-dobdc) and Ni<sub>2</sub>(<i>m</i>-dobdc) are able to separate 1-butene from the 2-butene isomers, a critical industrial process that relies largely on energetically demanding cryogenic distillation. The origin of 1-butene selectivity is traced to the high charge density retained by the M<sup>2+</sup> metal centers exposed within the M<sub>2</sub>(<i>m</i>-dobdc) structures, which results in a reversal of the <i>cis</i>-2-butene selectivity typically observed at framework open metal sites. Selectivity for 1-butene adsorption under multicomponent conditions is demonstrated for Ni<sub>2</sub>(<i>m</i>-dobdc) in both the gaseous and liquid phases via breakthrough and batch adsorption experiments.

Coordinatively unsaturated metal sites (open metal sites) in metal–organic frameworks: design and applications

2020 ◽  
Vol 49 (9) ◽  
pp. 2751-2798 ◽  
Author(s):  
Ülkü Kökçam-Demir ◽  
Anna Goldman ◽  
Leili Esrafili ◽  
Maniya Gharib ◽  
Ali Morsali ◽  
...  
Keyword(s):  
Metal Organic Frameworks ◽  
Supramolecular Interactions ◽  
Guest Molecules ◽  
Open Metal Sites ◽  
Metal Organic ◽  
Unsaturated Metal Sites

The defined synthesis of OMS in MOFs is the basis for targeted functionalization through grafting, the coordination of weakly binding species and increased (supramolecular) interactions with guest molecules.

scholarly journals Thermodynamic Separation of 1-Butene from 2-Butene in Metal–Organic Frameworks with Open Metal Sites

2019 ◽  
Author(s):  
Brandon Barnett ◽  
Surya Parker ◽  
Maria V. Paley ◽  
Miguel I. Gonzalez ◽  
Naomi Biggins ◽  
...  
Keyword(s):  
Metal Organic Frameworks ◽  
Industrial Process ◽  
Cost Effective ◽  
Oil Refining ◽  
Batch Adsorption ◽  
Metal Centers ◽  
Academic Effort ◽  
Liquid Phases ◽  
Open Metal Sites ◽  
Metal Organic

Most C<sub>4</sub> hydrocarbons are obtained as byproducts of ethylene production or oil refining, and complex and energy-intensive separation schemes are required for their isolation. Substantial industrial and academic effort has been expended to develop more cost-effective adsorbent- or membrane-based approaches to purify commodity chemicals such as 1,3-butadiene, isobutene, and 1-butene, but the very similar physical properties of these C<sub>4</sub> hydrocarbons makes this a challenging task. Here, we examine the adsorption behavior of 1-butene, <i>cis</i>-2-butene and <i>trans</i>-2-butene in the metal–organic frameworks M<sub>2</sub>(dobdc) (M = Mn, Fe, Co, Ni; dobdc<sup>2</sup><sup>−</sup> = 2,5-dioxidobenzene-1,4-dicarboxylate) and M<sub>2</sub>(<i>m</i>-dobdc) (<i>m</i>-dobdc<sup>4</sup><sup>−</sup> = 4,6-dioxido-1,3-benzenedicarboxylate), which all contain a high density of coordinatively-unsaturated M<sup>2+</sup> sites. We find that both Co<sub>2</sub>(<i>m</i>-dobdc) and Ni<sub>2</sub>(<i>m</i>-dobdc) are able to separate 1-butene from the 2-butene isomers, a critical industrial process that relies largely on energetically demanding cryogenic distillation. The origin of 1-butene selectivity is traced to the high charge density retained by the M<sup>2+</sup> metal centers exposed within the M<sub>2</sub>(<i>m</i>-dobdc) structures, which results in a reversal of the <i>cis</i>-2-butene selectivity typically observed at framework open metal sites. Selectivity for 1-butene adsorption under multicomponent conditions is demonstrated for Ni<sub>2</sub>(<i>m</i>-dobdc) in both the gaseous and liquid phases via breakthrough and batch adsorption experiments.

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