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Fluidized Catalytic cracking (FCC) is one of the main conversion processes in conventional refineries and employs a multicomponent catalyst with Y zeolite as the main source of activity and selectivity towards value added products. In order to meet the severe requirements of the FCC unit, the hydrothermal stability of this large pore zeolite is traditionally improved by means of controlled hydrothermal treatments that can be combined with acid washing cycles, with rare earth (RE) ion exchange or with a combination of both. Phosphorus has also been described as a hydrothermal stabilization element. Although most of the studies are based on ZSM-5 zeolites, a new Y zeolite containing FCC catalyst, Phinesse, was developed recently. This catalyst, based on the partial substitution of RE by P allowed obtaining the same activity and the same yields to the main products as its conventional RE stabilized counterpart in the catalytic cracking of a vacuum gas oil (VGO). In this work, we present a systematic study where the hydrothermal stability of P- and La-free USYs with different dealumination degrees is compared with that of the corresponding USYs containing P or La alone or a combination of both stabilizing elements. The samples have been thoroughly characterized and their catalytic performance has been tested in a MAT unit. According to the results obtained, when using RE alone, only high contents (> 3.5 wt% RE) are able to stabilize the catalysts towards steaming under severe conditions (100% steam, 750 ºC). However, lower RE ( wt%) can lead to similar hydrothermal stabilization when combined with intermediate phosphorus contents (∼1.0 wt%). The results obtained provide the bases for understanding the reasons behind the benefits of this combined P-La stabilization observed for the commercial Phinesse™ catalyst as compared to a high REO catalyst.

Simple aluminosilicates, including NaX and NaY zeolites, catalyze the selective halogen exchange reaction between two different alkyl organohalides, either in batch or in flow, without any additive or solvent, by simply heating at 130 °C and with <5 wt% of solid catalyst. The reaction protocol tolerates different functional groups and gives two new organohalides in good yields. Mechanistic studies unveil the key role of the zeolite oxygen atoms and countercations, to trigger the heterolytic scission of the R–X bond and generate intermediate alkoxy and halide species, respectively, which recombine within the zeolite framework. These results open a new way to synthesize organohalides with simple solid catalysts and expand the use of aluminosilicates in organic synthesis.

A new optimized photocatalyst for wastewater remediation at neutral pH has been developed and fully characterized. The catalyst features microparticles of SiO2 as a supporting substrate and a uniform shell of WO3 nanoparticles externally decorated with Fe3O4 nanocrystals. The photocatalytic activity of SiO2@WO3@Fe3O4 was evaluated and compared to its SiO2@WO3 counterpart on the photodegradation of methylene blue (MB) under visible light, with and without H2O2. Best results were obtained for SiO2@WO3@Fe3O4 in the presence of H2O2, whose potential for wastewater remediation was further evaluated on the photodegradation and mineralization of a contaminant of emerging concern such as diclofenac (DCF). Furthermore, a photocatalytic mechanism was proposed based on the performed electron paramagnetic resonance (EPR) experiments, which provided evidence for the intermediates generated in all the involved photocatalytic processes. Hence it was proven that .OH is the species responsible for the photocatalyzed oxidation of MB and DCF. The generation of .OH is boosted by a synergistic effect between Fe3O4 and WO3 in the presence of light and H2O2.

Commercially available zeolite Y modulates the catalytic activity and selectivity of ultrasmall silver species during the Buchner reaction and the carbene addition to methylene and hydroxyl bonds, by simply exchanging the counter cations of the zeolite framework. The zeolite acts as a macroligand to tune the silver catalytic site, enabling the use of this cheap and recyclable solid catalyst for the in situ formation of carbenes from diazoacetate and selective insertion in different C¿H (i.e., cyclohexane) and C¿O (i.e., water) bonds. The amount of catalyst in the reaction can be as low as ¿0.1 mol % silver. Besides, this reactivity allows deeply drying the HY zeolite framework by making the strongly adsorbed water molecules react with the in situ formed carbenes.

Metalloporphyrin-containing mesoporous materials, named VTPP@SBA, were prepared via a simple anchoring of vanadyl porphyrin (5,10,15,20-Tetraphenyl-21H,23H-porphine vanadium(IV) oxide) through a SBA-15-type mesoporous material. For comparison, vanadyl porphyrin was also impregnated on SiO (VTPP/SiO). The characterization results of catalysts by XRD, FTIR, DR-UV-vis, and EPR confirm the incorporation of vanadyl porphyrin within the mesoporous SBA-15. These catalysts have also been studied using electrochemical and photoelectrochemical methods. Impedance measurements confirmed that supporting the porphyrin in silica improved the electrical conductivity of samples. In fact, when using mesoporous silica, current densities associated with oxidation/reduction processes appreciably increased, implying an enhancement in charge transfer processes and, therefore, in electrochemical performance. All samples presented n-type semiconductivity and provided an interesting photoelectrocatalytic response upon illumination, especially silica-supported porphyrins. This is the first time that V-porphyrin-derived materials have been tested for photoelectrochemical applications, showing good potential for this use.

The nature of organic structure directing agents (OSDAs) is of paramount importance in the final properties of zeolites, particularly the framework and porosity. Recently, the use of P-containing OSDAs has been employed for new zeolites, but there is little discussion compared to their analogues N-OSDAs. The main objective of this work is the characterization of pure silica MFI zeolite (silicalite-1) prepared by the dual-template route with tetrapropylammonium (TPA), tetrapropylphosphonium (TPP) cations, and mixtures thereof aiming to understand by advanced NMR methods how the nature of the organic influences the physico-chemical properties of the zeolite. Silicalite-1 has been successfully synthesized using the dual-template procedure with TPA and TPP molecules. Both OSDAs are incorporated into the zeolite without any specific preference, differently to that observed before for the TEA/TEP system, and homogenously mixed inside of the zeolite voids. The presence of TPP leads to the incorporation of less F, raising the concentration of Q-defective sites in the silicalite-1 zeolites. Detailed NMR results indicate that those structural defects are close to the –CH group of the entrapped OSDAs in the zeolite and these defects consist of at least two silanol groups stabilizing the Si-O species, which is responsible for the charge balancing.

Supported silver species are among the most promising catalysts for the depletion of ammonia emission by selective catalytic oxidation (NH-SCO). Here, an investigation on the influence of small pore CHA and RHO zeolite structures on the silver species formed and their catalytic activity for the NH-SCO reaction has been conducted. To this end, AgRHO(4) and AgCHA(4) zeolites with similar Si/Al molar ratios (≈ 4) and silver content (∼15 wt%, Ag/Al ≈ 0.6), and AgCHA(2) with Si/Al ≈ 2 and higher silver loading, while maintaining the Ag/Al ratio (∼26 wt%, Ag/Al ≈ 0.6), have been submitted to different treatments and characterized by using a large variety of techniques (XRD, UV-Vis,Ag NMR,in situXAS andoperandoFT-IR). The reduction of the AgCHA and AgRHO zeolites at low temperature (100-200 °C) produces silver clusters, which remain in the AgRHO zeolite when the temperature is increased to 400 °C. However, the silver species in the AgCHA zeolites evolve to nanoparticles (NPs) at 400 °C under H. The catalytic tests show that metal particles are the active sites while silver clusters are inactive for the NH-SCO reaction. Also, there are important differences in the stability of the reduced Ag species under oxidizing or under reaction conditions at 400 °C. Metal NPs are partially redispersed and oxidized to (Ag), while silver clusters are completely oxidized to Ag. Our results indicate that silver clusters are stabilized in the RHO-type and not in the CHA-type zeolite, and thus they display very different catalytic activities for the NH-SCO reaction.

The chemical bulk reductive covalent functionalization of thin-layer black phosphorus (BP) using BP intercalation compounds has been developed. Through effective reductive activation, covalent functionalization of the charged BP by reaction with organic alkyl halides is achieved. Functionalization was extensively demonstrated by means of several spectroscopic techniques and DFT calculations; the products showed higher functionalization degrees than those obtained by neutral routes.

Group 15 elements in zero oxidation state (P, As, Sb and Bi), also called pnictogens, are rarely used in catalysis due to the difficulties associated in preparing well–structured and stable materials. Here, we report on the synthesis of highly exfoliated, few layer 2D phosphorene and antimonene in zero oxidation state, suspended in an ionic liquid, with the native atoms ready to interact with external reagents while avoiding aerobic or aqueous decomposition pathways, and on their use as efficient catalysts for the alkylation of nucleophiles with esters. The few layer pnictogen material circumvents the extremely harsh reaction conditions associated to previous superacid–catalyzed alkylations, by enabling an alternative mechanism on surface, protected from the water and air by the ionic liquid. These 2D catalysts allow the alkylation of a variety of acid–sensitive organic molecules and giving synthetic relevancy to the use of simple esters as alkylating agents.

Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of PdII SCCs within the confined space of a pre-formed MOF (SCCs@MOF) and its post-assembly metalation to give a PdII-AuIII supramolecular assembly, crystallography underpinned. These SCCs@MOFs catalyze the coupling of boronic acids and/or alkynes, representative multi-site metal-catalyzed reactions in which traditional SCCs tend to decompose, and retain their structural integrity as a consequence of the synergetic hybridization between SCCs and MOFs. These results open new avenues in both the synthesis of novel SCCs and their use in heterogeneous metal-based supramolecular catalysis.

Expanding the previously known family of -onium (ammonium, phosphonium, and sulfonium) organic structure-directing agents (OSDAs) for the synthesis of zeolite MFI, a new member, the arsonium cation, is used for the first time. The new group of tetraalkylarsonium cations has allowed the synthesis of the zeolite ZSM-5 with several different chemical compositions, opening a route for the synthesis of zeolites with a new series of OSDA. Moreover, the use of As replacing N in the OSDA allows the introduction of probe atoms that facilitate the study of these molecules by powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (MAS NMR), and X-ray absorption spectroscopy (XAS). Finally, the influence of trivalent elements such as B, Al, or Ga isomorphically replacing Si atoms in the framework structure and its interaction with the As species has been studied. The suitability of the tetraalkylarsonium cation for carrying out the crystallization of zeolites is demonstrated along with the benefit of the presence of As atoms in the occluded OSDA, which allows its advanced characterization as well as the study of its evolution during OSDA removal by thermal treatments.

Highly crystalline pure silica MFI zeolites have been synthesized using tetraethylammonium (TEA), tetraethylphosphonium (TEP), or a mixture of both cations in different proportions as organic structure directing agents (OSDAs). The zeolites have been deeply characterized in order to get insight about the guest-guest interactions involving the OSDAs and the guest-host interactions involving the OSDAs and the inorganic framework, as well as the main features of the resulting materials. The results show that the average size of the MFI crystals decreases when TEP is present within the zeolite and that this cation is homogeneously distributed throughout the crystallites. The multinuclear NMR investigation (H, C, N, F, Si, P) indicates that TEP interacts with the zeolite host creating higher heterogeneity of the SiO crystallographic sites and a diminution on the mobility of fluorine atoms incorporated into the zeolite. Moreover, the presence of TEP influences the dynamics of the nitrogen atoms of the TEA molecules, and 2D heteronuclear correlation experiments give evidence on the spatial proximity of the TEA and TEP molecules in the MFI zeolites. Then, it is concluded that TEA and TEP are intimately mixed within the zeolite voids of the pure silica MFI samples synthesized by the dual template route.

The catalysts used in the methanol-to-olefins (MTO) reaction are considered dual systems comprising an inorganic zeolite framework and organic compounds hosted inside that act as cocatalysts. The influence of zeolite cavity architecture on the preferential stabilization of cationic intermediates involved in the paring and side-chain routes of the hydrocarbon pool mechanism is analyzed by means of density functional theory (DFT) calculations, catalyst testing, and 13C NMR spectroscopy for some small-pore cage-based zeolites. A correlation between the degree of methylation of the entrapped methylbenzenium (MB+) cations and the selectivity to ethene and propene is found experimentally and explained in terms of the electronic distribution of the first intermediate of the paring route. A deep understanding of the reaction mechanism and of the specific host–guest interactions taking place inside zeolite catalysts allows establishing a quantitative parameter that is indicative for the contribution of the paring route and therefore the C3=/C2= ratio in the MTO reaction.

The development of contrast agents (CAs) for Magnetic Resonance Imaging (MRI) with T1–T2 dual-mode relaxivity requires the accurate assembly of T1 and T2 magnetic centers in a single structure. In this context, we have synthesized a novel hybrid material by monitoring the formation of Prussian Blue analogue Gd(H2O)4[Fe(CN)6] nanoparticles with tailored shape (from nanocrosses to nanorods) and size, and further protection with a thin and homogeneous silica coating through hydrolysis and polymerization of silicate at neutral pH. The resulting Gd(H2O)4[Fe(CN)6]@SiO2 magnetic nanoparticles are very stable in biological fluids. Interestingly, this combination of Gd and Fe magnetic centers closely packed in the crystalline network promotes a magnetic synergistic effect, which results in significant improvement of longitudinal relaxivity with regards to soluble Gd3+ chelates, whilst keeping the high transversal relaxivity inherent to the iron component. As a consequence, this material shows excellent activity as MRI CA, improving positive and negative contrasts in T1- and T2-weighted MR images, both in in vitro (e.g., phantom) and in vivo (e.g., Sprague-Dawley rats) models. In addition, this hybrid shows a high biosafety profile and has strong ability to incorporate organic molecules on the surface with variable functionality, displaying great potential for further clinical application.

Novel aluminium MOF-type materials structured by 1D subdomains, such as organic-inorganic nanoribbons, were synthesized by modifying the conditions of solvothermal synthesis and the nature of the solvents in the presence of aryl monocarboxylate linkers with long alkyl chains, which acted as growth-modulating agents. Specifically, three different families of materials were prepared with various morphological characteristics: (i) isoreticular MIL-53(Al)-type materials, (ii) mesoscopic metalorganic structures and (iii) lamellar aluminium MOFs. The length of the alkyl chain in the aryl linker and the hydrophobic/hydrophilic nature of the solvothermal synthesis media determined the structuration level that was achieved. The derived Al-MOFs are active and stable catalysts for the synthesis of fine chemicals. This was illustrated by the efficient synthesis of 2,3-dihydro-2,2,4-trimethyl-1H-1,5-benzodiazepine.

Controlling the location of acid sites in zeolites can have a great effect on catalysis. In this work we face the objective of directing the location of Al into the 10R channels of ZSM-5 by taking advantage of the structural preference of B to occupy certain positions at the channel intersections, as suggested by theoretical calculations. The synthesis of B-Al-ZSM-5 zeolites with variable Si/Al and Si/B ratios, followed by B removal in a postsynthesis treatment, produces ZSM-5 samples enriched in Al occupying positions at 10R channels. The location of the acid sites is determined on the basis of the product distribution of 1-hexene cracking as a test reaction. The higher selectivity to propene and lower C /C ratio in the samples synthesized with B and subsequently deboronated can be related to a larger concentration of acid sites in 10R channels, where monomolecular cracking occurs. Finally, several ZSM-5 samples have been tested in the methanol to propene reaction, and those synthesized through the B-assisted method show longer catalytic lifetime, higher propene yield, and lower yield of alkanes and aromatics.

We describe the synthesis, characterization and application as contrast agents in magnetic resonance imaging of a novel type of magnetic nanoparticle based on Gd-Si oxide, which presents high Gd3+ atom density. For this purpose, we have used a Prussian Blue analogue as the sacrificial template by reacting with soluble silicate, obtaining particles with nanorod morphology and of small size (75 nm). These nanoparticles present good biocompatibility and higher longitudinal and transversal relaxivity values than commercial Gd3+ solutions, which significantly improves the sensitivity of in vivo magnetic resonance images.