Examinando por Autor "Calleja, Guillermo"

Mostrando 1 - 16 de 16

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.
Amino functionalized mesostructured SBA-15 silica for CO2 capture: Exploring the relation between the adsorption capacity and the distribution of amino groups by TEM
(Elsevier, 2012) Sanz, Raúl; Calleja, Guillermo; Arencibia, Amaya; Sanz-Pérez, Eloy S.
The distribution of amino groups on amino-functionalized SBA-15 materials for CO2 adsorption was studied by Transmission Electron Microscopy (TEM) in combination with a staining technique using RuO4 in order to analyse the influence of the aminated organic chains location on the CO2 adsorption properties. Mesostructured aminofunctionalized SBA-15 materials were obtained by co-condensation, grafting and impregnation using aminopropyl, AP (N), ethylene-diamine, ED (NN), diethylenetriamine, DT (NNN) and polyethyleneimine, PEI, as functionalizing agents. CO2 adsorption isotherms of functionalized samples at 45 ºC showed that both the adsorption capacity (mg CO2/g ads) and the efficiency of amino groups (mol CO2/mol N) depend on the functionalization technique and the amount of organic compound used. While samples synthesized by co-condensation showed negligible CO2 uptake and efficiency, adsorbents prepared by grafting and impregnation presented significant CO2 adsorption capacities but a dissimilar efficiency. Key differences in the location of aminated chains explained the performance of CO2 capture for every adsorbent, being grafted samples the adsorbents where amino groups were better distributed, favouring the CO2 diffusion trough the whole structure.
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.
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 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.
Hf/porphyrin-based metal-organic framework PCN-224 for CO2 cycloaddition with epoxides
(Elsevier, 2023) Carrasco, Sergio; Orcajo, Gisela; Martínez, Fernando; Imaz, Inhar; Kavak, Safiyye; Arenas-Esteban, Daniel; Maspoch, Daniel; Bals, Sara; Calleja, Guillermo; Horcajada, Patricia
Herein, we describe for the first time the synthesis of the highly porous Hf-tetracarboxylate porphyrinbased metal-organic framework (MOF) (Hf)PCN-224(M) (M ¼ H2, Co2þ). (Hf)PCN-224(H2) was easily and efficiently prepared following a simple microwave-assisted procedure with good yields (56e67%; spacetime yields: 1100e1270 kg m3 $day1 ), high crystallinity and phase purity by using trifluoromethanesulfonic acid and benzoic acid as modulators in less than 30 min. By simply introducing a preliminary step (10 min), 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin linker (TCPP) was quantitatively metalated with Co2þ without additional purification and/or time consuming protection/deprotection steps to further obtain (Hf)PCN-224(Co). (Hf)PCN-224(Co) was then tested as catalyst in CO2 cycloaddition reaction with different epoxides to yield cyclic carbonates, showing the best catalytic performance described to date compared to other PCNs, under mild conditions (1 bar CO2, room temperature, 18 e24 h). Twelve epoxides were tested, obtaining from moderate to excellent conversions (35e96%). Moreover, this reaction was gram scaled-up (x50) without significant loss of yield to cyclic carbonates. (Hf)PCN-224(Co) maintained its integrity and crystallinity even after 8 consecutive runs, and poisoning was efficiently reverted by a simple thermal treatment (175 C, 6 h), fully recovering the initial catalytic activity.
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%.
Mesostructured SiO2-doped TiO2 with enhanced thermal stability prepared by a soft-templating sol-gel route
(ELSEVIER, 2008) Calleja, Guillermo; Serrano, David P.; Sanz, Raúl; Pizarro, Patricia
Mesostructured SiO2-TiO2 mixed oxides have been prepared by a soft-templating sol-gel route, using a non-ionic triblock copolymer as structure directing agent. Tetraethylorthosilicate (TEOS) and titanium tetraisopropoxide (TTIP) have been employed as Si and Ti sources, respectively. Using a prehydrolysis TEOS step allows mixed oxides to be produced with a homogeneous porosity and with no phase segregation, in a wide range of Si/Ti compositions. Both the hydrolysis molar ratio and the silicon content have been found to be important factors determining the final properties of these materials. For instance, mixed oxides containing low silicon concentrations exhibit N2 physisorption isotherms typical of mesoporous materials, although with an important contribution of microporosity. On the other hand, increasing the hydrolysis molar ratio makes more difficult to reach a total dispersion of SiO2 through the TiO2 matrix. Even with low SiO2 loadings, the thermal stability is effectively enhanced, when compared to the equivalent pure TiO2 materials, as a consequence of a delay in the titania crystallization to anatase. Thus, after calcination at 300 ºC for 3 h, mixed oxides containing low Si/Ti ratios (¿ 20) show BET surface area in the range 290-346 m2/g, while pure TiO2 materials largely collapse under the same treatment and their BET surface area drop strongly to values around 125 m2/g. This synthesis route, therefore, provides mesoporous TiO2-rich materials with enhanced stability and textural properties, which is of high interest for applications as catalysts and supports.
Nanocomposite of crystalline Fe2O3 and CuO particles and mesostructured SBA-15 silica as an active catalyst for wet peroxide oxidation processes
(ELSEVIER, 2006) Melero, Juan A.; Calleja, Guillermo; Martinez, Fernando; Molina, Raul
Crystalline Fe2O3 and CuO particles have been incorporated into surfactant-templated SBA-15 materials by direct synthesis. Activity and stability of this material were evaluated on the wet peroxide oxidation of phenol under mild reaction conditions. Its catalytic performance was monitored in terms of total organic carbon (TOC) conversion. The stability was determined by careful measurements of metal leaching into the aqueous solution. The presence of copper prevents the leaching of iron species and increases TOC degradation as compared with those materials containing only crystalline Fe2O3 particles. Moreover, the treatment of iron-copper composite materials under controlled acidic conditions in the presence of hydrogen peroxide leads to the stabilization of metallic species, maintaining TOC degradation rates similar to the fresh catalyst. Thus, this work introduces a new material with interesting properties as Fenton-like catalysts in advanced oxidation processes for pollutant abatement in wastewaters.
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.
Novel Titanocene-Tartrate complexes as catalysts for the asymmetric epoxidation of allylic alcohols
(ELSEVIER, 2007) van Grieken, Rafael; Garcia, Rafael A.; Calleja, Guillermo; Iglesias, Jose
This communication presents the synthesis of novel titanocene-based chiral complexes and their application as catalysts for asymmetric oxidation reactions. These new complexes drive the catalytic asymmetric oxidation of allylic alcohols without the requirement of low temperature conditions, a usual drawback in asymmetric synthesis. Results from catalytic studies shows the enantioselectivity of these chiral complexes strongly depends on the steric hindrances caused by the chiral ligand and the alkyl hydroperoxide oxidant around the titanium centre.
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.