Francesc X. Llabrés i Xamena

Metal–organic framework nanosheets in polymer composite materials for gas separation

Composites incorporating two-dimensional nanostructures within polymeric matrices hold potential as functional components for several technologies, including gas separation. Prospectively, employing metal-organic-frameworks (MOFs) as versatile nanofillers would notably broaden the scope of functionalities. However, synthesizing MOFs in the form of free standing nanosheets has proven challenging. We present a bottom-up synthesis strategy for dispersible copper 1,4-benzenedicarboxylate MOF lamellae of micrometer lateral dimensions and nanometer thickness. Incorporating MOF nanosheets into polymer matrices endows the resultant composites with outstanding CO2 separation performance from CO2/CH4 gas mixtures, together with an unusual and highly desired increment in the separation selectivity with pressure. As revealed by tomographic focused-ion-beam scanning-electron-microscopy, the unique separation behaviour stems from a superior occupation of the membrane cross-section by the MOF nanosheets as compared to isotropic crystals, which improves the efficiency of molecular discrimination and eliminates unselective permeation pathways. This approach opens the door to ultrathin MOF-polymer composites for various applications.

Water Stable Zr-Benzenedicarboxylate Metal-Organic Frameworks as Photocatalysts for Hydrogen Generation

The Zr-containing metal-organic frameworks (MOFs) formed by terephthalate (UiO-66) and 2-aminoterephthalate ligands [UiO-66(NH(2))] are two notably water-resistant MOFs that exhibit photocatalytic activity for hydrogen generation in methanol or water/methanol upon irradiation at wavelength longer than 300 nm. The apparent quantum yield for H(2) generation using monochromatic light at 370 nm in water/methanol 3:1 was of 3.5% for UiO-66(NH(2)). Laser-flash photolysis has allowed detecting for UiO-66 and UiO-66(NH(2)) the photochemical generation of a long lived charge separated state whose decay is not complete 300 μs after the laser flash. Our finding and particularly the influence of the amino group producing a bathochromic shift in the optical spectrum without altering the photochemistry shows promises for the development of more efficient MOFs for water splitting.

Cu and Au Metal–Organic Frameworks Bridge the Gap between Homogeneous and Heterogeneous Catalysts for Alkene Cyclopropanation Reactions

The copper and gold metal-organic frameworks (MOFs) [Cu(3)(BTC)(2)(H(2)O)(3)](n), [Cu(3)(BTC)(2)] (BTC=benzene-1,3,5-tricarboxylate), and IRMOF-3-SI-Au are active and reusable solid catalysts for the cyclopropanation of alkenes with high chemo- and diastereoselectivities. This type of material gives better results than previous solid catalysts while working together with the homogeneous catalysts. These MOFs can help to bridge the gap between homogeneous and heterogeneous catalysis.

Metal Organic Frameworks as Heterogeneous Catalysts

1. Introduction PART A. SYNTHESIS AND CHARACTERIZATION OF MOFs 2. Synthesis of MOFs 3. Post-synthetic Modification of MOFs 4. Characterization of MOFs. 1. Combined Vibrational and Electronic Spectroscopies 5. Characterization of MOFs. 2. Long and Local Range Order Structural Determination of MOFs by Combining EXAFS and Diffraction Techniques 6. MOFs for Energy and Environmental Applications 7. Computational Approach to Chemical Reactivity of MOFs PART B. CATALYSIS BY MOFs 8. Strategies for Creating Active Sites in MOFs 9. Catalysis at the Metallic Nodes of MOFs 10. Catalysis at the Organic Ligands 11. MOFs as Nanoreactors. Species Encapsulated in the IntraMOF Space 12. Asymmetric Catalysis with Chiral MOFs 13. Photocatalysis by MOFs 14. Catalysis by Covalent Organic Frameworks (COFs) 15. Conclusions and Future Developments

MOFs as Multifunctional catalysts: Synthesis of secondary arylamines, quinolines, pyrroles and arylpyrrolidines over bifunctional MIL-101

Bifunctional MIL‐101 MOFs containing Lewis acid Cr3+ sites and Pd or Pt hydrogenation/reduction centers, either as isolated metal complexes or in the form of encapsulated metal nanoparticles, have shown to be highly active catalysts for the one‐pot nitroarene reduction and reductive amination of carbonyl compounds. This preparation procedure has been successfully applied to the synthesis of secondary arylamines, quinolines, pyrrols, and 3‐arylpyrrolidines. In all the cases, the MOFs have shown superior performances with respect to commercially available Pd and Pt metal catalysts under the same conditions.

Encapsulation of bimetallic metal nanoparticles into robust zirconium-based metal–organic frameworks: Evaluation of the catalytic potential for size-selective hydrogenation

The realization of metal nanoparticles (NPs) with bimetallic character and distinct composition for specific catalytic applications is an intensively studied field. Due to the synergy between metals, most bimetallic particles exhibit unique properties that are hardly provided by the individual monometallic counterparts. However, as small-sized NPs possess high surface energy, agglomeration during catalytic reactions is favored. Sufficient stabilization can be achieved by confinement of NPs in porous support materials. In this sense, metal-organic frameworks (MOFs) in particular have gained a lot of attention during the last years; however, encapsulation of bimetallic species remains challenging. Herein, the exclusive embedding of preformed core-shell PdPt and RuPt NPs into chemically robust Zr-based MOFs is presented. Microstructural characterization manifests partial retention of the core-shell systems after successful encapsulation without harming the crystallinity of the microporous support. The resulting chemically robust NP@UiO-66 materials exhibit enhanced catalytic activity towards the liquid-phase hydrogenation of nitrobenzene, competitive with commercially used Pt on activated carbon, but with superior size-selectivity for sterically varied substrates.

CHAPTER 14:Towards Future MOF Catalytic Applications

In this last chapter of the book, we highlight additional aspects, also very relevant for the future application of MOFs in catalytic processes at the industrial scale, but that have not been explicitly treated in the other chapters. On one hand, we discuss the potential of (multi-functional) MOF catalysts for one-pot tandem reactions or multicomponent coupling reactions as a means of process intensification to improve the economy of the system. On the other hand, we highlight the different approaches followed for the shaping of MOF catalysts, one of the critical steps before industrial implementation.

CHAPTER 7:Strategies for Creating Active Sites in MOFs

This chapter presents a general overview of the main properties of MOFs that make them very appealing for applications in heterogeneous catalysis. Great efforts have been directed in the last decade to study the potential of MOFs in catalysis. We will now see what is behind this “MOF rush”. Next, we will present some general considerations that should be taken into account when planning the use of MOFs as heterogeneous catalysts, such as stability, recovery and reusability. And finally, we will review the different strategies that can be used to introduce the desired catalytic centers into the MOFs. We will show how it is possible by using these strategies to engineer the material for catalysis, and to fine tune the properties of the MOF to influence the catalytic performance.