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Catalytic Processes Mediated by Metal−Organic Frameworks: Reactivity and Mechanistic Studies
Stockholm University, Faculty of Science, Department of Organic Chemistry. (Belen Martin Matute)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis describes the development of heterogeneous catalytic methodologies using metal−organic frameworks (MOFs) as porous matrices for supporting transition metal catalysts. A wide spectrum of chemical reactions is covered. Following the introductory section (Chapter 1), the results are divided between one descriptive part (Chapter 2) and four experimental parts (Chapters 3–6).

Chapter 2 provides a detailed account of MOFs and their role in heterogeneous catalysis. Specific synthesis methods and characterization techniques that may be unfamiliar to organic chemists are illustrated based on examples from this work.

Pd-catalyzed heterogeneous C−C coupling and C−H functionalization reactions are studied in Chapter 3, with focus on their practical utility. A vast functional group tolerance is reported, allowing access to substrates of relevance for the pharmaceutical industry. Issues concerning the recyclability of MOF-supported catalysts, leaching and operation under continuous flow are discussed in detail.

The following chapter explores puzzling questions regarding the nature of the catalytically active species and the pathways of deactivation for Pd@MOF catalysts. These questions are addressed through detailed mechanistic investigations which include in situ XRD and XAS data acquisition. For this purpose a custom reaction cell is also described in Chapter 4.

The scope of Pd@MOF-catalyzed reactions is expanded in Chapter 5. A strategy for boosting the thermal and chemical robustness of MOF crystals is presented. Pd@MOF catalysts are coated with a protecting SiO2 layer, which improves their mechanical properties without impeding diffusion. The resulting nanocomposite is better suited to withstand the harsh conditions of aerobic oxidation reactions. In this chapter, the influence of the nanoparticles’ geometry over the catalyst’s selectivity is also investigated.

While Chapters 3–5 dealt with Pd-catalyzed processes, Chapter 6 introduces hybrid materials based on first-row transition metals. Their reactivity is explored towards light-driven water splitting. The heterogenization process leads to stabilized active sites, facilitating the spectroscopic probing of intermediates in the catalytic cycle.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University , 2016. , 122 p.
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-132711ISBN: 978-91-7649-485-1OAI: oai:DiVA.org:su-132711DiVA: diva2:953881
Public defence
2016-10-07, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 8: Submitted.

 

Available from: 2016-09-14 Created: 2016-08-19 Last updated: 2016-09-02Bibliographically approved
List of papers
1. Sustainable Catalysis: Rational Pd Loading on MIL-101Cr-NH2 for More Efficient and Recyclable Suzuki-Miyaura Reactions
Open this publication in new window or tab >>Sustainable Catalysis: Rational Pd Loading on MIL-101Cr-NH2 for More Efficient and Recyclable Suzuki-Miyaura Reactions
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2013 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 51, 17483-17493 p.Article in journal (Refereed) Published
Abstract [en]

Palladium nanoparticles have been immobilized into an amino-functionalized metal-organic framework (MOF), MIL-101Cr-NH2, to form Pd@MIL-101Cr-NH2. Four materials with different loadings of palladium have been prepared (denoted as 4-, 8-, 12-, and 16wt%Pd@MIL-101Cr-NH2). The effects of catalyst loading and the size and distribution of the Pd nanoparticles on the catalytic performance have been studied. The catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), N-2-sorption isotherms, elemental analysis, and thermogravimetric analysis (TGA). To better characterize the palladium nanoparticles and their distribution in MIL-101Cr-NH2, electron tomography was employed to reconstruct the 3D volume of 8wt%Pd@MIL-101Cr-NH2 particles. The pair distribution functions (PDFs) of the samples were extracted from total scattering experiments using high-energy X-rays (60keV). The catalytic activity of the four MOF materials with different loadings of palladium nanoparticles was studied in the Suzuki-Miyaura cross-coupling reaction. The best catalytic performance was obtained with the MOF that contained 8wt% palladium nanoparticles. The metallic palladium nanoparticles were homogeneously distributed, with an average size of 2.6nm. Excellent yields were obtained for a wide scope of substrates under remarkably mild conditions (water, aerobic conditions, room temperature, catalyst loading as low as 0.15mol%). The material can be recycled at least 10times without alteration of its catalytic properties.

Keyword
cross-coupling, heterogeneous catalysts, metal-organic frameworks, nanoparticles, palladium
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-99879 (URN)10.1002/chem.201302621 (DOI)000327889800030 ()
External cooperation:
Funder
Knut and Alice Wallenberg FoundationSwedish Research CouncilVINNOVACarl Tryggers foundation
Note

AuthorCount:9;

Available from: 2014-01-24 Created: 2014-01-20 Last updated: 2016-08-25Bibliographically approved
2. Highly Functionalized Biaryls via Suzuki-Miyaura Cross-Coupling Catalyzed by Pd@MOF under Batch and Continuous Flow Regimes
Open this publication in new window or tab >>Highly Functionalized Biaryls via Suzuki-Miyaura Cross-Coupling Catalyzed by Pd@MOF under Batch and Continuous Flow Regimes
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2015 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 8, no 1, 123-130 p.Article in journal (Refereed) Published
Abstract [en]

A diverse set of more than 40 highly functionalized biaryls was synthesized successfully through the Suzuki-Miyaura cross-coupling reaction catalyzed by Pd nanoparticles supported in a functionalized mesoporous MOF (8 wt% Pd@MIL-101(Cr)-NH2). This could be achieved under some of the mildest conditions reported to date and a strong control over the leaching of metallic species could be maintained, despite the presence of diverse functional groups and/or several heteroatoms. Some of the targeted molecules are important intermediates in the synthesis of pharmaceuticals and we clearly exemplify the versatility of this catalytic system, which affords better yields than currently existing commercial procedures. Most importantly, Pd@MIL-101-NH2 was packed in a micro-flow reactor, which represents the first report of metallic nanoparticles supported on MOFs employed in flow chemistry for catalytic applications. A small library of 11 isolated compounds was created in a continuous experiment without replacing the catalyst, demonstrating the potential of the catalyst for large-scale applications.

Keyword
flow chemistry, heterocycles, MOF catalysis, suzuki-miyaura
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-113697 (URN)10.1002/cssc.201402858 (DOI)000347541700015 ()
External cooperation:
Note

AuthorCount:8;

Available from: 2015-03-18 Created: 2015-02-09 Last updated: 2016-08-25Bibliographically approved
3. Selective Heterogeneous C−H Activation/Halogenation Reactions Catalyzed by Pd@MOF Nanocomposites
Open this publication in new window or tab >>Selective Heterogeneous C−H Activation/Halogenation Reactions Catalyzed by Pd@MOF Nanocomposites
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2016 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 11, 3729-3737 p.Article in journal (Refereed) Published
Abstract [en]

A directed heterogeneous C−H activation/halogenation reaction catalyzed by readily synthesized Pd@MOF nanocatalysts was developed. The heterogeneous Pd catalysts used were a novel and environmentally benign Fe-based metal–organic framework (MOF) (Pd@MIL-88B-NH2(Fe)) and the previously developed Pd@MIL-101-NH2(Cr). Very high conversions and selectivities were achieved under very mild reaction conditions and in short reaction times. A wide variety of directing groups, halogen sources, and substitution patterns were well tolerated, and valuable polyhalogenated compounds were synthesized in a controlled manner. The synthesis of the Pd-functionalized Fe-based MOF and the recyclability of the two catalysts are also presented.

National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-132704 (URN)10.1002/chem.201502918 (DOI)000371741400027 ()26481867 (PubMedID)
External cooperation:
Available from: 2016-08-19 Created: 2016-08-19 Last updated: 2016-08-26Bibliographically approved
4. Influence of the Base on Pd@MIL-101-NH2(Cr) as Catalyst for the Suzuki-Miyaura Cross-Coupling Reaction
Open this publication in new window or tab >>Influence of the Base on Pd@MIL-101-NH2(Cr) as Catalyst for the Suzuki-Miyaura Cross-Coupling Reaction
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2015 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 30, 10896-10902 p.Article in journal (Refereed) Published
Abstract [en]

The chemical stability of metal-organic frameworks (MOFs) is a major factor preventing their use in industrial processes. Herein, it is shown that judicious choice of the base for the Suzuki-Miyaura cross-coupling reaction can avoid decomposition of the MOF catalyst Pd@MIL-101-NH2(Cr). Four bases were compared for the reaction: K2CO3, KF, Cs2CO3 and CsF. The carbonates were the most active and achieved excellent yields in shorter reaction times than the fluorides. However, powder XRD and N-2 sorption measurements showed that the MOF catalyst was degraded when carbonates were used but remained crystalline and porous with the fluorides. XANES measurements revealed that the trimeric chromium cluster of Pd@MIL-101-NH2(Cr) is still present in the degraded MOF. In addition, the different countercations of the base significantly affected the catalytic activity of the material. TEM revealed that after several catalytic runs many of the Pd nanoparticles (NPs) had migrated to the external surface of the MOF particles and formed larger aggregates. The Pd NPs were larger after catalysis with caesium bases compared to potassium bases.

Keyword
cross-coupling, heterogeneous catalysis, metal-organic frameworks, nanoparticles, palladium
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-119544 (URN)10.1002/chem.201500843 (DOI)000357984900039 ()
External cooperation:
Available from: 2015-08-20 Created: 2015-08-17 Last updated: 2016-08-26Bibliographically approved
5. Probing the active catalytic species generated from Pd(II)@MIL-101-NH2 in Heck coupling reactions: An operando X-ray absorption spectroscopy study
Open this publication in new window or tab >>Probing the active catalytic species generated from Pd(II)@MIL-101-NH2 in Heck coupling reactions: An operando X-ray absorption spectroscopy study
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(English)Article in journal (Refereed) Submitted
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-132706 (URN)
External cooperation:
Available from: 2016-08-19 Created: 2016-08-19 Last updated: 2016-08-26Bibliographically approved
6. Double-Supported Silica-Metal-Organic Framework Palladium Nanocatalyst for the Aerobic Oxidation of Alcohols under Batch and Continuous Flow Regimes
Open this publication in new window or tab >>Double-Supported Silica-Metal-Organic Framework Palladium Nanocatalyst for the Aerobic Oxidation of Alcohols under Batch and Continuous Flow Regimes
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2015 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 2, 472-479 p.Article in journal (Refereed) Published
Abstract [en]

Stable and easily synthesized metal-organic framework MIL-88B-NH2 represents an attractive support for catalysts employed in oxidation reactions, which are typically performed under relatively harsh conditions. However, MIL-88B-NH2, the thermodynamic polymorph of the more popular MIL-101-NH2, has been rarely employed in catalytic applications because of a difficult impregnation process caused by the flexible nature of the framework. We report herein a new catalyst denoted Pd@MIL-88B-NH2 (8 wt % Pd), the first example of metallic nanoparticles successfully impregnated in the pores of MIL-88B-NH2. Furthermore, by enclosing the MOF crystals in a tailored protective coating of SiO2 nanoparticles, an even more enduring material was developed and applied to the aerobic oxidation of benzylic alcohols. This doubly supported catalyst Pd@MIL-88B-NH2@nano-SiO2 displayed high activity and excellent performance in terms of endurance and leaching control. Under batch conditions, a very convenient and efficient recycling protocol is illustrated, using a teabag approach. Under continuous flow, the catalyst was capable of withstanding 7 days of continuous operation at 110 degrees C without deactivation. During this time, no leaching of metallic species was observed, and the material maintained its structural integrity.

Keyword
palladium nanoparticles, MIL-88B-NH2, aerobic oxidation, teabag catalysis, flow chemistry
National Category
Chemical Sciences
Research subject
Inorganic Chemistry; Organic Chemistry
Identifiers
urn:nbn:se:su:diva-115697 (URN)10.1021/cs501573c (DOI)000349275300001 ()
External cooperation:
Note

AuthorCount:10;

Available from: 2015-03-30 Created: 2015-03-27 Last updated: 2016-08-26Bibliographically approved
7. Mild and Selective Catalytic Hydrogenation of the C=C Bond in a,b-Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles
Open this publication in new window or tab >>Mild and Selective Catalytic Hydrogenation of the C=C Bond in a,b-Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles
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2016 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 21, 7184-7189 p.Article in journal (Refereed) Published
Abstract [en]

Chemoselective reduction of the C=C bond in a variety of α,β-unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H2: 1) nano-Pd on a metal–organic framework (MOF: Pd0-MIL-101-NH2(Cr)), 2) nano-Pd on a siliceous mesocellular foam (MCF: Pd0-AmP-MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd0-MIL-101-NH2(Cr) and Pd0-AmP-MCF were capable of delivering the desired products in very short reaction times (10–90 min) with low loadings of Pd (0.5–1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching.

National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-132708 (URN)10.1002/chem.201600878 (DOI)
External cooperation:
Available from: 2016-08-19 Created: 2016-08-19 Last updated: 2016-08-25Bibliographically approved
8. A MOF-Supported H2 Evolution Photocatalyst with Remarkable Stability and Improved Efficiency
Open this publication in new window or tab >>A MOF-Supported H2 Evolution Photocatalyst with Remarkable Stability and Improved Efficiency
(English)Article in journal (Refereed) Submitted
National Category
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-132709 (URN)
Available from: 2016-08-19 Created: 2016-08-19 Last updated: 2016-08-19

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