Mixed gas adsorption of carbon dioxide and methane on a series of isoreticular microporous metal-organic frameworks based on 2-substituted imidazolate-4-amide-5-imidates

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In this work the adsorption of CO2 and CH4 on a series of isoreticular microporous metal–organic frameworks based on 2-substituted imidazolate-4-amide-5-imidates, IFP-1–IFP-6 (IFP = Imidazolate Framework Potsdam), is studied firstly by pure gas adsorption at 273 K. All experimental isotherms can be nicely described by using the Tòth isotherm model and show the preferred adsorption of CO2 over CH4. At low pressures the Tòth isotherm equation exhibits a Henry region, wherefore Henry's law constants for CO2 and CH4 uptake could be determined and ideal selectivity αCO2/CH4 has been calculated. Secondly, selectivities were calculated from mixture data by using nearly equimolar binary mixtures of both gases by a volumetric–chromatographic method to examine the IFPs. Results showed the reliability of the selectivity calculation. Values of αCO2/CH4 around 7.5 for IFP-5 indicate that this material shows much better selectivities than IFP-1, IFP-2, IFP-3, IFP-4 and IFP-6 with slightly lower selectivity αCO2/CH4 = 4–6. The preferred adsorption of CO2 over CH4 especially of IFP-5 and IFP-4 makes these materials suitable for gas separation application.DFG, SPP 1362, Poröse metallorganische Gerüstverbindunge

Cobalt Amide Imidate Imidazolate Frameworks as Highly Active Oxygen Evolution Model Materials

Two imidazolate-based Co-MOFs, IFP-5 and IFP-8 (imidazolate framework Potsdam), with a different peripheral group -R (-Me and -OMe, respectively) have been synthesized by a solvothermal method and tested toward the oxygen evolution reaction (OER). Remarkably, IFP-8 presents much lower overpotentials (319 mV at 10 mA/cm2 and 490 mV at 500 mA/cm2) than IFP-5 toward OER, as confirmed by online gas chromatography measurements (Faradaic yield of O2 > 99%). Moreover, the system is extraordinarily stable during 120 h, even when used as a catalyst toward the overall water splitting reaction without any sign of fatigue. An integrated ex situ spectroscopic study, based on powder X-ray diffraction, extended X-ray absorption fine structure, and attenuated total reflection, allows the identification of the active species and the factors that determine the catalytic activity. Indeed, it was found that the performances are highly affected by the nature of the -R group, because this small change strongly influences the conversion of the initial metal organic framework to the active species. As a consequence, the remarkable activity of IFP-8 can be ascribed to the formation of Co(O)OH phase with a particle size of a few nanometers (3-10 nm) during the electrocatalytic oxygen evolution. Copyright © 2019 American Chemical Society.We thank the ICIQ Foundation, the European Research Foundation for project H2020-ERC-2015-CoG (J.L.-F.), H2020-FETPROACT-01-2016 A-LEAF (J.L.-F./A.B.), MINECO (CTQ2016-80038-R; J.L-F. and CTQ2017-86936-P; A.S.) and AGAUR 2017-SGR-1647 (J.L.-F.). S.S.M. thanks COFUND for postdoctoral scholarship. We would like to thank the support of the SAMBA beamline at the SOLEIL synchrotron (France) for their support and time for data acquisition. We thank to Prof. H.-J Holdt (University of Potsdam) for ligand precursor supplying.Peer reviewe

Cobalt Amide Imidate Imidazolate Frameworks as Highly Active Oxygen Evolution Model Materials

Two imidazolate-based Co-MOFs, IFP-5 and IFP- 8 (imidazolate framework Potsdam), with a different peripheral group −R (−Me and −OMe, respectively) have been synthesized by a solvothermal method and tested toward the oxygen evolution reaction (OER). Remarkably, IFP-8 presents much lower overpotentials (319 mV at 10 mA/cm2 and 490 mV at 500 mA/cm2) than IFP-5 toward OER, as confirmed by online gas chromatography measurements (Faradaic yield of O2 > 99%). Moreover, the system is extraordinarily stable during 120 h, even when used as a catalyst toward the overall water splitting reaction without any sign of fatigue. An integrated ex situ spectroscopic study, based on powder X-ray diffraction, extended X-ray absorption fine structure, and attenuated total reflection, allows the identification of the active species and the factors that determine the catalytic activity. Indeed, it was found that the performances are highly affected by the nature of the −R group, because this small change strongly influences the conversion of the initial metal organic framework to the active species. As a consequence, the remarkable activity of IFP-8 can be ascribed to the formation of Co(O)OH phase with a particle size of a few nanometers (3−10 nm) during the electrocatalytic oxygen evolution

Highly Active Oxygen Evolution Electrocatalysts Based on Cobalt Amide Imidate Imidazolate Frameworks

A family of three imidazolate-based Co-MOFs, IFP-5, -8 and -10 (Imidazolate Framework Potsdam), with different peripheral group –R (-Me, -OMe and –OEt, respectively) have been synthesized by a solvothermal method and tested toward oxygen evolution reaction (OER). Remarkably, IFP-8 presents low overpotentials (319 mV at 10 mA/cm2, and 490 mV at 500 mA/cm2) and extraordinary stability during 120 h, even when used as a catalyst toward overall water splitting reaction. An integrated ex-situ spectroscopic study, based on PXRD, EXAFS, and ATR, allows the identification of the active species and the factors that rule the catalytic activity. Indeed, it was found that the performances are highly affected by the nature of the -R group, because this small change strongly influences the conversion of the initial MOF to the active species. As a consequence, the remarkable activity of IFP-8 can be ascribed to the formation of Co(O)OH phase of few nanometers particle size (3-10 nm) during the electrocatalytic oxygen evolution. </p

Characterization of an Isostructural MOF Series of Imidazolate Frameworks Potsdam by Means of Sorption Experiments with Water Vapor

Sorption measurements of water vapor on an isoreticular series of Imidazolate Frameworks Potsdam (IFP), based on penta-coordinated metal centers with secondary building units (SBUs) connected by multidentate amido-imidate-imidazolate linkers, have been carried out at 303.15 K. The isotherm shapes were analyzed in order to gain insight into material properties and compared to sorption experiments with nitrogen at 77.4 K and carbon dioxide at 273.15 K. Results show that water vapor sorption measurements are strongly influenced by the pore size distribution while having a distinct hysteresis loop between the adsorption and desorption branch in common. Thus, IFP-4 and -8, which solely contain micropores, exhibit H4 (type I) isotherm shapes, while those of IFP-1, -2 and -5, which also contain mesopores, are of H3 (type IV) shape with three inflection points. The choice of the used linker substituents and transition metals employed in the framework has a tremendous effect on the material properties and functionality. The water uptake capacities of the examined IFPs are ranging 0.48 mmol g−1 (IFP-4) to 6.99 mmol g−1 (IFP-5) and comparable to those documented for ZIFs. The water vapor stability of IFPs is high, with the exception of IFP-8

Characterization of an Isostructural MOF Series of Imidazolate Frameworks Potsdam by Means of Sorption Experiments with Water Vapor

Sorption measurements of water vapor on an isoreticular series of Imidazolate Frameworks Potsdam (IFP), based on penta-coordinated metal centers with secondary building units (SBUs) connected by multidentate amido-imidate-imidazolate linkers, have been carried out at 303.15 K. The isotherm shapes were analyzed in order to gain insight into material properties and compared to sorption experiments with nitrogen at 77.4 K and carbon dioxide at 273.15 K. Results show that water vapor sorption measurements are strongly influenced by the pore size distribution while having a distinct hysteresis loop between the adsorption and desorption branch in common. Thus, IFP-4 and -8, which solely contain micropores, exhibit H4 (type I) isotherm shapes, while those of IFP-1, -2 and -5, which also contain mesopores, are of H3 (type IV) shape with three inflection points. The choice of the used linker substituents and transition metals employed in the framework has a tremendous effect on the material properties and functionality. The water uptake capacities of the examined IFPs are ranging 0.48 mmol g????1 (IFP-4) to 6.99 mmol g????1 (IFP-5) and comparable to those documented for ZIFs. The water vapor stability of IFPs is high, with the exception of IFP-8

Characterization of an Isostructural MOF Series of Imidazolate Frameworks Potsdam by Means of Sorption Experiments with Water Vapor

Sorption measurements of water vapor on an isoreticular series of Imidazolate Frameworks Potsdam (IFP), based on penta-coordinated metal centers with secondary building units (SBUs) connected by multidentate amido-imidate-imidazolate linkers, have been carried out at 303.15 K. The isotherm shapes were analyzed in order to gain insight into material properties and compared to sorption experiments with nitrogen at 77.4 K and carbon dioxide at 273.15 K. Results show that water vapor sorption measurements are strongly influenced by the pore size distribution while having a distinct hysteresis loop between the adsorption and desorption branch in common. Thus, IFP-4 and -8, which solely contain micropores, exhibit H4 (type I) isotherm shapes, while those of IFP-1, -2 and -5, which also contain mesopores, are of H3 (type IV) shape with three inflection points. The choice of the used linker substituents and transition metals employed in the framework has a tremendous effect on the material properties and functionality. The water uptake capacities of the examined IFPs are ranging 0.48 mmol g????1 (IFP-4) to 6.99 mmol g????1 (IFP-5) and comparable to those documented for ZIFs. The water vapor stability of IFPs is high, with the exception of IFP-8

Crystal‐to‐Crystal Synthesis of Photocatalytic Metal–Organic Frameworks for Visible‐Light Reductive Coupling and Mechanistic Investigations

Postmodification of reticular materials with well‐defined catalysts is an appealing approach to produce new catalytic functional materials with improved stability and recyclability, but also to study catalysis in confined spaces. A promising strategy to this end is the postfunctionalization of crystalline and robust metal–organic frameworks (MOFs) to exploit the potential of crystal‐to‐crystal transformations for further characterization of the catalysts. In this regard, two new photocatalytic materials, MOF‐520‐PC1 and MOF‐520‐PC2, are straightforwardly obtained by the postfunctionalization of MOF‐520 with perylene‐3‐carboxylic acid (PC1) and perylene‐3‐butyric acid (PC2). The single crystal‐to‐crystal transformation yielded the X‐ray diffraction structure of catalytic MOF‐520‐PC2. The well‐defined disposition of the perylenes inside the MOF served as suitable model systems to gain insights into the photophysical properties and mechanism by combining steady‐state, time‐resolved, and transient absorption spectroscopy. The resulting materials are active organophotoredox catalysts in the reductive dimerization of aromatic aldehydes, benzophenones, and imines under mild reaction conditions. Moreover, MOF‐520‐PC2 can be applied for synthesizing gram‐scale quantities of products in continuous‐flow conditions under steady‐state light irradiation. This work provides an alternative approach for the construction of well‐defined, metal‐free, MOF‐based catalysts.We thank the ICIQ Foundation, the European Research Foundation for project ERC‐2014‐CoG 648304 (J.L.‐F.), MINECO (CTQ2016‐80038‐R; J.L.‐F.), and AGAUR 2017‐SGR‐1647 (J.L.‐F.) for funding. S.S.M. and N.K. are grateful to Marie‐Curie COFUND and JyC for postdoctoral scholarships, respectively.Peer reviewe

Microwave-assisted synthesis of defects metal-imidazolate-amide-imidate frameworks and improved CO2 capture

In this work, we report three isostructural 3D frameworks, named IFP-11 (R = Cl), IFP-12 (R = Br), and IFP-13 (R = Et) (IFP = Imidazolate Framework Potsdam) based on a cobalt(II) center and the chelating linker 2-substituted imidazolate-4-amide-5-imidate. These chelating ligands were generated in situ by partial hydrolysis of 2-substituted 4,5-dicyanoimidazoles under microwave (MW)-assisted conditions in DMF. Structure determination of these IFPs was investigated by IR spectroscopy and a combination of powder X-ray diffraction (PXRD) with structure modeling. The structural models were initially built up from the single-crystal X-ray structure determination of IFP-5 (a cobalt center and 2-methylimidazolate-4-amide-5-imidate linker based framework) and were optimized by using density functional theory calculations. Substitution on position 2 of the linker (R = Cl, Br, and Et) in the isostructural IFP-11, -12, and -13 allowed variation of the potential pore window in 1D hexagonal channels (3.8 to 1.7 Å). The potential of the materials to undergo specific interactions with CO2 was measured by the isosteric heat of adsorption. Further, we resynthesized zinc based IFPs, namely IFP-1 (R = Me), IFP-2 (R = Cl), IFP-3 (R = Br), and IFP-4 (R = Et), and cobalt based IFP-5 under MW-assisted conditions with higher yield. The transition from a nucleation phase to the pure crystalline material of IFP-1 in MW-assisted synthesis depends on reaction time. IFP-1, -3, and -5, which are synthesized by MW-assisted conditions, showed an enhancement of N2 and CO2, compared to the analogous conventional electrical (CE) heating method based materials due to crystal defects

Giant Zn₁₄ Molecular Building Block in Hydrogen-Bonded Network with Permanent Porosity for Gas Uptake

<i>In situ</i> imidazolate-4,5-diamide-2-olate linker generation leads to the formation of a [Zn₁₄(L2)₁₂(O)­(OH)₂(H₂O)₄] molecular building block (MBB) with a Zn₆ octahedron inscribed in a Zn₈ cube. The MBBs connect by amide–amide hydrogen bonds to a 3D robust supramolecular network which can be activated for N₂, CO₂, CH₄, and H₂ gas sorption