Examinando por Autor "Leo, Pedro"

Mostrando 1 - 20 de 20

A double basic Sr-amino containing MOF as a highly stable heterogeneous catalyst
(Royal Society of Chemistry, 2019-07-03) Leo, Pedro; Orcajo, Gisela; Briones, David; Rodríguez-Dieguez, Antonio; Choquesillo-Lazarte, Duane; Calleja, Guillermo; Martínez, Fernando
A novel metal–organic framework (MOF) based on strontium alkaline-earth metal and 2-amino-1,4-benzenedicarboxylic acid (NH2-bdc) has been developed. This material is formed by a linear succession of face-sharing strontium polyhedra bridged by an organic ligand molecule to give a three-dimensional network with rhombohedral one-directional channels. This MOF is stable in polar organic solvents and up to 250 °C. The basic catalytic activity of both strontium metal nodes and amino groups of the ligand was tested in Knoevenagel condensation reactions. The influence of the temperature and reaction solvent over the catalytic performance of the MOF catalyst was demonstrated. The strontium/amino-containing MOF material evidenced a remarkable activity as compared to other conventional alkaline oxides typically used as reference basic solid catalysts. The novel MOF material showed remarkable activity and structural stability during five consecutive catalytic runs with no evidence of activity loss under the best reaction conditions found in this study.
A novel Zn-based-MOF for efficient CO2 adsorption and conversion under mild conditions
(Elsevier, 2021) Tapiador, Jesús; Leo, Pedro; Rodríguez-Diéguez, Antonio; Choquesillo-Lazarte, Duane; Calleja, Guillermo; Orcajo, Gisela
A novel Zn-based-MOF material, called Zn-URJC-8, containing two different organic linkers, 2-aminoterephtallic acid and 4,4-bipyridyl, has been synthetized and used for catalytic purposes for the first time. The structure of Zn-URJC-8 has been determined by single-crystal X-ray diffraction (XRD) showing -NH2 groups inward-facing of narrow pores, providing the material with excellent properties as CO2 adsorbent. The good results obtained by means of carbon dioxide adsorption isotherms have demonstrated the high interaction between CO2 and -NH2 groups with a Qst value of 54 kJ/mol at low coverage. The Zn-URJC-8 material also display promising results as catalyst for CO2 transformation in added value products. Almost complete conversion of epichlorohydrin and CO2 in cycloaddition reaction has been achieved under mild conditions, and the influence of different radical groups coordinated to the epoxides has been evaluated on the reaction yield. The recyclability has been also tested and the structural integrity of the catalyst is maintained after several consecutive reaction cycles.
Aldol condensation of furfural and methyl isobutyl ketone over Zr-MOF-808/silica hybrid catalysts
(Elsevier, 2023) Morales, Gabriel; Paniagua, Marta; Flor, Daniel de la; Sanz, María; Leo, Pedro; López-Aguado, Clara; Hernando, Héctor; Orr, Samantha A.; Wilson, Karen; Lee, Adam F.; Melero, Juan A.
Mesoporous silica-supported Zr-MOF-808 catalysts have been synthesised and tested in the aldol condensation of (biomass-derived) furfural and methyl isobutyl ketone to bio-jet fuel precursors. Growth of Zr-MOF-808 nanocrystals over silica scaffolds results in well-dispersed Zr species which confer strong Lewis acidity as determined by FTIR of chemisorbed pyridine. Hybrid Zr-MOF-808/silica materials exhibit higher condensation activity than the unsupported crystalline Zr-MOF-808 (which is also prone to rapid deactivation). Textural properties of the silica support strongly influence the catalytic performance, with a high surface area and sufficiently large mesopore desirable. In the screening, the optimum Zr-MOF-808/MCM-41 catalyst delivered 68 % furfural conversion and 90 % selectivity to the C11 aldol adduct, 1-(furan-2-yl)-5-methylhex-1-en-3-one, at 130 ◦C and a furfural:Zr mass ratio of 150:1. Although more stable than the pure Zr-MOF-808, the Zr-MOF-808/MCM-41 also suffered significant deactivation over successive condensation reactions due to strongly adsorbed organic residues, however this was largely ameliorated by decreasing the furfural:Zr ratio to 75:1, which also led to an outstanding catalytic performance (100 % furfural conversion and adduct selectivity), likely because of the suppression of furfural polymerization.
Boosting the activity of UiO-66(Zr) by defect engineering: efficient aldol condensation of furfural and MIBK for the production of bio jet-fuel precursors
(Royal Society of Chemistry, 2024-05-30) Sanz, María; Leo, Pedro; Palomino, Carlos; Paniagua, Marta; Morales, Gabriel; Melero, Juan A.
The production of jet-fuel precursors from furfural via aldol-condensation with methyl-isobutyl ketone (MIBK) over defect-engineered UiO-66(Zr) catalysts is presented. The catalysts are prepared using formic acid (FA), trifluoroacetic acid (TFA) and HCl as synthesis modulators, leading to the incorporation of defects on the microcrystalline structure of the metalorganic framework (MOF) material, which dramatically boosts the catalytic performance. An extensive characterization of the modified catalysts by means of X-ray diffraction (XRD), argon adsorption isotherm, thermogravimetry (TGA), transmission electron microscopy, and FTIR spectroscopy of adsorbed acetonitrile, confirmed the incorporation of missing-linker and missing-node defects within the MOF structure, enabling the explanation of the enhancement in the catalytic process. The analysis of the reaction kinetics evidences that, working under moderate temperature conditions, conversion of furfural and selectivity to the desired adduct (FuMe) close to 100% can be achieved, avoiding the formation of degradation and bulkier compounds. Finally, despite the generation of defects within the UiO-66(Zr) structure, the resultant catalyst displays good reusability in low furfural concentration mediums.
Catalytic activity and stability of sulfonic-functionalized UiO-66 and MIL-101 materials in friedel-crafts acylation reaction
(Elsevier, 2022-05-01) Leo, Pedro; Crespí, Neus; Palomino, Carlos; Martín, Antonio; Orcajo, Gisela; Calleja, Guillermo; Martínez, Fernando
Sulfonic-containing UiO-66 and MIL-101 MOF materials, prepared by direct synthesis with a sulfonic acid-including benzene dicarboxylate (SO3H-BDC) linker, have been evaluated as acid catalysts in Friedel–Crafts acylation of anisole with acetic anhydride. The catalytic activity of these materials was compared to other conventional acidic sulfonic heterogeneous catalysts, such as commercial Nafion-SAC-13 and Amberlyst-15. The catalytic performance of MOF materials was significantly dependent on their textural properties and the availability of sulphonic acid groups. MIL-101-SO3H material displayed a remarkable anisole conversion and specific activity per sulfonic acid centre due to its open structure and multimodal pore size distribution. The inherent properties of MIL-101-SO3H material allowed a more sustainable catalyst regeneration than those used for conventional heterogeneous catalysts due to the deposition of reagents and products, in particular poly-acetylated compounds. MIL-101-SO3H proved an easy recovery and reusability in successive runs without any loss of activity. These promising results evidenced the potential of MIL-101-SO3H as an alternative catalyst for acid-catalyzed reactions.
Catalytic Advantages of SO3H-Modified UiO-66(Zr) Materials Obtained via Microwave Synthesis in Friedel–Crafts Acylation Reaction
(American Chemical Society, 2024-09-03) Bauza, Marta; Leo, Pedro; Palomino Cabello, Carlos; Martín, Antonio; Orcajo, Gisela; Turnes Palomino, Gemma; Martínez, Fernando
The catalytic activity and stability of sulfonic-based UiO-66(Zr) materials were tested in the Friedel–Crafts acylation of anisole with acetic anhydride. The materials were prepared using microwave-assisted synthesis, producing microporous materials with remarkable crystallinity and physicochemical features as acid catalysts. Different ratios between both organic ligands, terephthalic acid (H2BDC) and monosodium 2-sulfoterephthalic acid (H2BDC–SO3Na), were used for the synthesis to modulate the sulfonic content. The sulfonic-based UiO-66(Zr) material synthesized with a H2BDC/H2BDC–SO3Na molar ratio of 40/60 exhibited the best catalytic performance in the acidic-catalyzed Friedel–Crafts acylation reaction. This ratio balanced the number of sulfonic acid sites and their accessibility within the UiO-66 microporous structure. The catalytic performance of this material increased remarkably at 200 °C, outperforming reference acids and commercial heterogeneous catalysts such as Nafion-SAC-13 and Amberlyst-70. Additionally, the best sulfonic-based UiO-66(Zr) material proved to be stable in four successive reaction cycles, maintaining both its catalytic activity and its structural integrity
Catalytical advantages of Hf-MOFs in benzaldehyde acetalization
(Elsevier, 2024-05-15) García-Rojas, Elena; Tapiador, Jesús; Leo, Pedro; Palomino, Carlos; Martos, Carmen; Orcajo, Gisela
The potential use of acetals as bioadditives based on sustainable feedstocks in the automotive industry is of great interest. If such feedstock is a residual stream, the process would represent a dual environmental challenge, such as the valorization of glycerol obtained as a by-product of biodiesel to produce acetals. There are just scarce works about this synthetic route due to the challenge in finding efficient catalytic converters for glycerol valorization in a single process. Herein four different Metal-Organic Frameworks (MOFs) are evaluated as heterogeneous catalysts for the acetalization reaction of benzaldehyde with methanol, specifically, two structures, MOF-808 and UiO-66, containing two structural metal ions, zirconium and hafnium. The aim of this work is to investigate the influence of the MOF structure, the metallic active sites and the reaction conditions on the catalytic performance of this acetal production-type reaction. Furthermore, the recyclability of the catalyst is evaluated, and a potential reaction mechanism is suggested. As relevant results, Hf-MOFs showed higher benzaldehyde conversion than Zr-based ones, and significant improvements in reaction conditions were achieved, such as a significant reduction in catalyst loading of 99.6 % using UiO-66-Hf, and an optimization of reagent ratios reducing methanol consumption by 50 % for a 92 % of benzaldehyde conversion. The Brønsted character of UiO-66-Hf seems to enhance the reaction rate more than the metal center accessibility and larger pore volumes offered by MOF-808
Copper MOFs performance in the cycloaddition reaction of CO2 and epoxides
(Elsevier, 2023) Tapiador, Jesús; García-Rojas, Elena; Leo, Pedro; Martos, Carmen; Calleja, Guillermo; Orcajo, Gisela
The research in advanced materials for effective CO2 capture and conversion is an imperative duty for the next years. In this sense MOF materials are being intensively tested for this purpose. Herein, seven different copperbased MOF materials with different functional organic groups in their linkers have been assessed to comprehend some structural features that influence the CO2 transformation via cycloaddition reaction with epoxides: CuURJC-1 (tetrazole group), Cu-URJC-8 (primary amine group), Cu-MOF-74 (hydroxyl group), JUC-62 (azo group), PCN-16 (triple bond group), HNUST-1 (amide group) and HKUST-1. When epichlorohydrin was used as a substrate, Cu-URJC-8 produced the best epoxide conversion (90%) and selectivity to cyclic carbonate (>99%), despite showing a modest surface area. This result can be explained by the higher basicity of primary amines than other basic functional organic groups of the MOFs. However, when styrene oxide was used as substrate, CuURJC-1 led to the best reaction results with a conversion and selectivity toward cyclic carbonate of 60 and 86%, respectively. This result was achieved because this material presents the synergic effect of having in its flexible structure 12 Å channels, that favors the styrene oxide diffusion, and a great number of basic nitrogen atoms, which can increase the reactivity of carbon dioxide. In summary, the presence of nitrogen atoms in the organic linker increases the CO2 conversion by promoting the reactivity of this molecule.
Direct Synthesis of MOF-74 Materials on Carbon Fiber Electrodes for Structural Supercapacitors
(MDPI, 2024-01-20) Martínez-Díaz, David; Leo, Pedro; Martín Crespo, David; Sánchez, María; Ureña, Alejandro
The use of fossil fuels has contributed significantly to environmental pollution and climate change. For this reason, the development of alternative energy storage devices is key to solving some of these problems. The development of lightweight structures can significantly reduce the devices’ weight, thereby reducing energy consumption and emissions. Combining lightweight structures with alternative energy storage technologies can further improve efficiency and performance, leading to a cleaner and more sustainable system. In this work, for the first time, MOF-74 materials with different divalent metal ions have been synthesized directly on carbon fiber, one of the most widely used materials for the preparation of electrodes for supercapacitors with structural properties. Different techniques, such as nitrogen adsorption–desorption isotherms, cyclic voltammetry or galvanostatic charge–discharge, among others, were used to evaluate the influence of the metal cation on the electrochemical capacitance behavior of the modified electrodes. The Co-MOF-74 material was selected as the best modification of the carbon fibers for their use as electrodes for the fabrication of structural supercapacitors. The good electrochemical performance shown after the incorporation of MOF materials on carbon fibers provides a viable method for the development of carbon fiber electrodes, opening a great variety of alternatives.
Direct α-arylation of ketones efficiently catalyzed by Cu-MOF-74
(Elsevier, 2019-09-19) Leo, Pedro; Orcajo, Gisela; Briones, David; Martínez, Fernando; Calleja, Guillermo
The activity and reusability of Cu-MOF-74 as heterogeneous catalyst were studied in the Cu-catalyzed CeC crosscoupling reaction of 4-iodotoluene (4-IT) with acetylacetone (AcAc) to direct synthesis of α-aryl-ketones. CuMOF-74 is characterized by having unsaturated copper sites into its highly porous metal-organic framework that can play a crucial role in catalytic applications. The influence of critical reaction variables such as solvent, reaction temperature, AcAc/4-IT ratio, catalyst concentration and basic agent (type and concentration) were evaluated. High conversions were achieved at 140°C, 5mol % of catalyst, AcAc/4-IT ratio of 2:1, DMF as solvent and 1.5 equivalent of Cs2CO3 base. The C-arylation between 4-IT and AcAc proceeded only in the presence of CuMOF-74 material, being very low the transformation in absence of the solid catalyst. Cu-MOF-74 material displayed a remarkable structural stability, regarding its XRD patterns and solid recovery degree after several reaction cycles, which was also complemented by the negligible amount of copper leached in the reaction media. This catalyst showed promising results in comparison to other homogeneous and heterogeneous Cu-based catalysts. This work evidences the great potential of MOF materials as heterogeneous catalysts in fine chemistry applications.
Guest-induced structural deformation in Cu-based metal-organic framework upon hydrocarbon adsorption
(Elsevier, 2023-06-17) Luna-Triguero, Azahara; Andres-García, Eduardo; Leo, Pedro; Rook, Willy; Kapteijn, Freek
In a world where capture and separation processes represent above 10% of global energy consumption, novel porous materials, such as Metal-Organic Frameworks (MOFs) used in adsorption-based processes are a promising alternative to dethrone the high-energy-demanding distillation. Shape and size tailor-made pores in combination with Lewis acidic sites can enhance the adsorbate-adsorbent interactions. Understanding the underlying mechanisms of adsorption is essential to designing and optimizing capture and separation processes. Herein, we analyze the adsorption behaviour of light hydrocarbons (methane, ethane, ethylene, propane, and propylene) in two synthesized copper-based MOFs, Cu-MOF-74 and URJC-1. The experimental and computational adsorption curves reveal a limited effect of the exposed metal centers on the olefins. The lower interaction Cu-olefin is also reflected in the calculated enthalpy of adsorption and binding geometries. Moreover, the diamond-shaped pores’ deformation upon external stimuli is first reported in URJC-1. This phenomenon is highlighted as the key to understanding the adsorbent’s responsive mechanisms and potential in future industrial applications.
Improving Oxidative Catalytic Efficiency for Fuels Desulfurization Using Hybrid Materials Based in MOF-808@SBA-15Improving Oxidative Catalytic Efficiency for Fuels Desulfurization Using Hybrid Materials Based in MOF-808@SBA-15
(Wiley, 2024-04-11) C. Fernandes, Simone; Leo, Pedro; Santos-Vieira, Isabel; de Castro, Baltazar; Cunha-Silva, Luis; S. Balula, Salete
This work unveils a route for a new generation of heterogeneous polyoxometalate (POMs) based catalysts associated to the preparation of hybrid materials as a triad of POMs, mesoporous silica (SBA-15) and microporous MOF structures (MOF-808). The prepared catalyst, PMo12@MOF-808@SBA-15, with the main active center the phosphomolybdic acid (PMo12), was successfully applied for the desulfurization of a multicomponent fuel. Its oxidative catalytic performance showed to be considerable superior to the isolated POM@MOF and able to be recycled for more catalytic cycles without active loss. The higher catalytic performance seems to be directly related with the preparation of a more amorphous MOF structure within the channels of SBA-15, in the presence of active POM guests.
Influence of divalent metal ions on CO2 valorization at room temperature by isostructural MOF-74 materials
(Elsevier, 2023) Tapiador, J.; García-Rojas, E.; López-Patón, P.; Calleja, Guillermo; Orcajo, Gisela; Martos, Carmen; Leo, Pedro
At present, the concentration of carbon dioxide (CO2) has increased to unprecedented levels. The valorization of CO2 into high value-added chemicals can be a very interesting alternative to stabilize the concentration of this atmospheric pollutant while the current energy transition takes place. The well-known M-MOF-74 family (M= Mg, Co, Ni, Cu and Zn) have been evaluated as heterogeneous catalysts to carry out several cycloaddition reactions at room temperature with several epoxides (epichlorohydrin; 1,2-epoxyhexane and styrene oxide) as substrate, to evaluate the influence of the metal in this reaction. Zn-MOF-74 showed the highest catalytic activity, always with conversion and selectivity values above 93% regardless of the epoxides studied and the carbonates obtained, due to the higher acid character of the Zn2+ ion. Therefore, it is confirmed that the influence of the metal is key in this reaction, despite the fact that Cu-MOF-74 with an adsorption capacity of 5 mmol/g of CO2 (45 ◦C, 5 bar) converts 26% of styrene oxide under the conditions evaluated compared to ZnMOF-74, which is the material with the lowest adsorption capacity (3 mmol/g of CO2) and shows a conversion of 93%.
MOF-808 as an Efficient Catalyst for Valorization of Biodiesel Waste Production: Glycerol Acetalization
(MDPI, 2023-11-03) Mirante, Fátima; Leo, Pedro; N. Dias, Catarina; Cunha-Silva, Luis; S. Balula, Salete
Glycerol is the main residue in the biodiesel production industry; therefore, their valorization is crucial. The acetalization of glycerol toward fuel additives such as solketal (2,2-dimethyl1,3-dioxolan-4-methanol) is of high interest, promoting circular economy since it can be added to biodiesel or even fossil diesel to improve their quality and efficiency. Straightforward-prepared metal–organic framework (MOF) materials of the MOF-808 family were applied to the valorization of glycerol for the first time. In particular, MOF-808(Hf) was revealed to be an effective heterogeneous catalyst to produce solketal under moderate conditions: a small amount of the MOF material (only 4 wt% of glycerol), a 1:6 ratio of glycerol/acetone, and a temperature of 333 K. The high efficiency of MOF-808(Hf) was associated with the high amount of acid centers present in its structure. Furthermore, its structural characteristics, such as window opening cavity size and pore diameters, were shown to be ideal for reusing this material for at least ten consecutive reaction cycles without losing activity (conversion > 90% and selectivity > 98%). Remarkably, it was not necessary to wash or activate the MOF-808(Hf) catalyst between cycles (no pore blockage occurred), and it maintained structural integrity after ten cycles, confirming its ability to be a sustainable heterogeneous catalyst for glycerol valorization.
Novel and Versatile Cobalt Azobenzene-Based Metal-Organic Framework as Hydrogen Adsorbent
(Wiley, 2019-01-18) Montes-Andres, Helena; Leo, Pedro; Orcajo, Gisela; Rodríguez-Dieguez, Antonio; Choquesillo-Lazarte, Duane; Martos, Carmen; Botas, Juan Ángel; Martínez, Fernando; Calleja, Guillermo
A novel URJC-3 material based on cobalt and 5,5′-(diazene-1,2-diyl)diisophthalate ligand, containing Lewis acid and basic sites, has been synthesized under solvothermal conditions. Compound URJC-3, with polyhedral morphology, crystallizes in the tetragonal and P43212 space group, exhibiting a three-dimensional structure with small channels along a and b axes. This material was fully characterized, and its hydrogen adsorption properties were estimated for a wide range of temperatures (77–298 K) and pressures (1–170 bar). The hydrogen storage capacity of URJC-3 is quite high in relation to its moderate surface area, which is probably due to the confinement effect of hydrogen molecules inside its reduced pores of 6 Å, which is close the ionic radii of hydrogen molecules. The storage capacity of this material is not only higher than that of active carbon and purified single-walled carbon nanotubes, but also surpasses the gravimetric hydrogen uptake of most MOF materials.
Open Zn-URJC-13 efficient catalyst for mild CO2 transformation using bulky epoxides
(Elsevier, 2023) Tapiador, Jesús; Leo, Pedro; Calleja, Guillermo; Orcajo, Gisela
In CO2 cycloaddition reactions with epoxides that have bulky or long-chain substituents, the yield significantly decreases when using heterogeneous catalysts, including MOFs, with micropores smaller than 14 Å. In this study, a new MOF material called Zn-URJC-13 is reported. This MOF combines different features such as that it contains acid and basic Lewis sites based on Zn and -NH2 groups, exhibits permanent porosity with a bimodal porous system centered at 11 and 17 Å suitable for the diffusion of cycloaddition reaction species, and it is chemically stable in various common organic solvents. The aim of this material is to improve the textural properties of other MOFs with similar chemical compositions, making it suitable as a catalyst for CO2 cycloaddition reactions with epoxides even bulky. This novel material exhibits high affinity to CO2 molecules, with a Qst of 62 kJ/mol. The Zn-URJC-13 catalyst demonstrates efficient performance in CO2 cycloaddition reactions using a wide range of epoxides, including those with long-chain and bulky substituents such as allyl glycidyl ether and styrene oxide. It can achieve an epoxide conversion as high as 84 % and selectivity to carbonate products above 90 % for the bulkiest styrene oxide. When compared to other Zn-based MOF materials with similar or different structures but without amino groups, the new material exhibits superior catalytic performance. Furthermore, Zn-URJC-13 can be reused in five consecutive reaction cycles while maintaining its efficient catalytic behavior and crystalline structure. These findings highlight the notable potential of Zn-URJC-13 for CO2 cycloaddition transformation routes.
Robust Cu-URJC-8 with mixed ligands for mild CO2 cycloaddition reaction
(Elsevier, 2022) Tapiador, Jesús; Leo, Pedro; Gándara, Felipe; Calleja, Guillermo; Orcajo, Gisela
The synthesis of the new MOF Cu-URJC-8, containing two different organic ligands, 2-aminoterephtalic acid and 4,4-bipyridyl, is reported in this work. Cu-URJC-8 shows a pillared-layer structure consisting of [Cu2(-CO2)4(- N)2] paddlewheel secondary building units, with the 4,4’-bypiridyl linkers acting as pillars in the two-fold interpenetrated networks, which provides a robust structure to the material. Cu-URJC-8 presents Lewis acid and basic sites, constituted by Cu2+ and -NH2 groups, respectively, and it is chemically stable in different commonly used organic solvents. This new material shows a CO2 uptake of 1.59 and 1.07 mmol/g at 25 and 45 ◦C, respectively, and a Qst value of 27 kJ/mol, higher than those observed for other reported MOFs with higher textural properties, possibly due to the presence of amino groups in the MOF structure. Its catalytic activity in the cycloaddition reaction of epichlorohydrin and CO2 was evaluated under various conditions and the best performance (90 conversion and 99% selectivity) was achieved when using 1% mol of catalyst, 4% mol of co-catalyst, 12 bar of carbon dioxide pressure, and room temperature. When different epoxides with bulkier radical groups are used as substrates, the epoxide conversion decreases, evidencing steric hindrances for diffusion inside cavities of Cu-URJC-8. Finally, Cu-URJC-8 has a high stability, keeping its structural integrity and catalytic activity after successive CO2 cycloaddition reaction cycles. These results show that Cu-URJC-8 is a promising catalyst for CO2 revalorization.
Synthesis, Structural Features, and Hydrogen Adsorption Properties of Three New Flexible Sulfur-Containing Metal–Organic Frameworks
(American Chemical Society, 2020-08-31) Montes-Andres, Helena; Leo, Pedro; Orcajo, Gisela; Rodríguez-Dieguez, Antonio; Choquesillo-Lazarte, Duane; Martos, Carmen; Botas, Juan Ángel; Calleja, Guillermo
Three novel flexible sulfur-containing MOF materials named Co-URJC-5, Cu-URJC-6 and Zn-URJC-7, based on the 5,5′-thiodiisophthalic acid linker have been synthesized through solvothermal methods and characterized by different physicochemical techniques. Hydrogen adsorption analysis at room temperature reveals that these compounds display a gate-opening type adsorption mechanism at low pressures, attributed to the flexible nature of the H4TBTC ligand. This behavior is even more noticeable for Cu-URJC-6, since the layer arrangement by π–π stacking interactions between the aromatic layers could contribute to the flexibility of the structure. These results can be considered as a representative example to elucidate how MOF structures are built using flexible ligands and more significantly as a promising route for designing materials with selective gas sorption properties.
URJC-1-MOF as New Heterogeneous Recyclable Catalyst for C-Heteroatom Coupling Reactions
(Wiley, 2019-06-05) Muñoz, Antonio; Leo, Pedro; Orcajo, Gisela; Martínez, Fernando; Calleja, Guillermo
The capacity of copper-based URJC-1-MOF as a MOF catalyst in cross-coupling reactions has been evaluated, focusing on the Chan-Lam-Evans arylation-type reactions on amines and alcohols without extra additives or ligands. The extraordinary chemical and structural stability of URJC-1-MOF and its good specific surface, make this material a promising alternative to homogeneous Cu (II) catalysts for cross-coupling reactions. URJC-1-MOF showed a remarkable catalytic activity for cross-coupling C−N and C−O reactions, higher than other heterogeneous and homogeneous copper-based catalyst, such as CuO, HKUST-1, Cu−MOF-74, Cu(OAc)2 and CuSO4⋅5H2O. Moreover, its easy recovery by simple filtration and reusability in successive runs without any loss of activity and stability, demonstrates the potential of URJC-1-MOF as an alternative catalyst for this kind of reactions in different chemical media of industrial interest.
URJC-1: Stable and Efficient Catalyst for O-Arylation Cross-Coupling
(MDPI, 2024-06-27) García-Rojas, Elena; Leo, Pedro; Tapiador, Jesus; Martos, Carmen; Orcajo, Gisela
The design of metal–organic frameworks (MOFs) allows the definition of properties for their final application in small-scale heterogeneous catalysis. Incorporating various catalytic centers within a single structure can produce a synergistic effect, which is particularly intriguing for crosscoupling reactions. The URJC-1 material exhibits catalytic duality: the metal centers act as Lewis acid centers, while the nitrogen atoms of the organic ligand must behave as basic centers. The impact of reaction temperature, catalyst concentration, and basic agent concentration was evaluated. Several copper-based catalysts, including homogeneous and heterogeneous MOF catalysts with and without the presence of nitrogen atoms in the organic ligand, were assessed for their catalytic effect under optimal conditions. Among the catalysts tested, URJC-1 exhibited the highest catalytic activity, achieving complete conversion of 4-nitrobenzaldehyde with only 3% mol copper concentration in one hour. Furthermore, URJC-1 maintained its crystalline structure even after five reaction cycles, demonstrating remarkable stability in the reaction medium. The study also examined the impact of various substituents of the substrate alcohol on the reaction using URJC-1. The results showed that the reaction had high activity when activating substituents were present and for most cyclic alcohols rather than linear ones.