Research
(Photo)catalytic materials for organic synthesis
(Research line led by Rubén Mas-Ballesté)
What are the factors that determine the catalytic activity of a material? How the advantages of immobilizing catalytic centers can be enhanced? Is it possible to establish synergies in design materials that give rise to complex catalytic processes? These questions are addressed from a basic perspective, designing new extended materials based on condensation reactions of different types. We pay special attention to photocatalytic processes mediated by photoactive materials that owe their properties either to the insertion of functional fragments or to the synergistic assembly of building blocks that separately are inactive. Following these strategies we have reported efficient catalytic systems for the photocatalytic sulfoxidation of organic sulfides, C(sp2)-C(sp3) couplings, dehaolgenation reactions or highly recyclable systems for Suzuki or Heck type couplings.
ACS applied materials & interfaces, 2023, 15 (25) 30212–30219.
Applied Catalysis B: Environmental, 2022,121791
ACS applied materials & interfaces, 2022, 14, (14), 16258-16268.
Advanced Sustainable Systems, 2022, 6, (3), 2100409.
Catalysts, 2021, 11,(12), 1426.
ACS catalysis 2021, 11, (19), 12344-12354.
Applied Catalysis B: Environmental, 2020, 272,119027.
ChemCatChem, 2019, 11, (19), 4916-4922.
Catalysis Science & Technology , 2019, 9 (21), 6007-6014.
Materials recently studied
Ceramic nanoparticles: synthesis, characterization, and thin films formation.
(Research line led by mario Borlaf)
Colloidal sol-gel route is a low-cost synthesis that allows to obtain nanoparticles with a low particle size, low aggregation degree, and high stability (well dispersed in the reaction media, even for years). Ceramics such as TiO2, Nb2O5, TiNb2O7, CaTiO3, among others, even doped with other metal ions, can be synthesized at temperatures below 50 ºC and reaction times of minutes, hours, or days, depending on synthesis conditions. The nanoparticles can be easily deposited on substrates by dip-coating, spin-coating, spray coating, or electrophoretic deposition (EPD).
The synthesis of ceramic nanoparticles by Flame Spray Synthesis is a very powerful and versatile route. Spherical nanoparticles can be synthesized by burning out a solution containing the metal ions that will form the ceramic particle. This route has not been implemented yet in the laboratory.
J. Mater. Chem. A 2024,12, (9), 5156-5169.
Open Ceram. 2021, 8, 100200.
Catalysts 2020, 10, (9), 984.
J. Am. Chem. Soc. 2019, 141, (13), 5231-5240.
J. Am. Ceram. Soc. 2017,100, (89), 3784-3793.
Mater. Chem. Phys,. 2014,144, (1-2), 8-16.
Eur. J. Inorg. Chem. 2014, (30), 5152-5159.
Inverse vulcanization reactions to prepare ferrocenyl-containing sulfur-rich materials: electroactive sensors
(Research line led by Sonia Bruña)
Inverse vulcanization (IV) is an emergent route materialized a decade ago as an alternative to obtain polymers with a high sulfur content, also known as polysulfides. Sulfur is an exceptionally Earth-abundant element; besides it is produced in high quantities in oil refining and natural gas purification processes. However, its demand is still far from meeting its high levels of stock. In this regard, in the past years, IV has been exploited for reevaluating and enhancing sulfur uses in a sustainable and low-cost process, which is highly desirable. These reactions are carried out at temperatures above the melting point of sulfur (120 ⁰C), when a ring-opening polymerization (ROP) of the S8 ring occurs. Di-radicals (•(Sn)•), formed after the ROP, bind to unsaturated co-monomers (olefinic fragments) in a clean process, in which sulfur acts both as a reactant and as the reaction medium, avoiding the use of solvents.
We have recently developed a strategy, based on IV, to introduce physico-chemical properties to sulfur-based materials that are not specific of polysulfide fragments. In particular, novel redox-responsive polysulfide materials have been isolated as a consequence of including electroactive ferrocenyl moieties (C). In addition, these materials exhibit a synergistic ferrocene-sulfur effect, evidenced by their ability to electrochemically recognize environmental hazardous Hg2+ and Cd2+ soft metal centers. From a broader perspective, this strategy, based on the incorporation of redox-active building blocks on sulfur-based polymers through inverse vulcanization procedures, opens the door to a wide range of functional materials with applications related to metal centers, such as sensing or photocatalysis, in which we currently work to inactivate different kind of water pollutants.
Polymer Chemistry, 2024, 15, 1015-1025.
Water decontamination
(Research line led by Rubén Mas-Ballesté)
Availability of drinking water is an increasing challenge worldwide. In fact, water is related with many aspects of economic and social challenges, and it is, by itself, a main goal for sustainable development. However, nowadays, 2.2 billion people around the world do not have safely managed drinking water services. The consequences of such problem are not only local but also national and global in today’s interconnected world. Therefore, the search of new strategies for water disinfection and purification is still a global challenge. To this respect, owing the outstanding photocatalytic properties found for porous organic materials, we proffer to explore their practical applications for wastewater decontamination. In particular generation of singlet oxygen as a silver bullet is successfully applied to the degradation of several contaminants and to the inactivation of viruses. In addition, incorporation of highly coordinative fragments allows metal removal from aqueous solutions. Overall, the use of extended organic materials is being explored for the removal of three different kind of water pollutants: organic molecules, pathogens, such as bacteria and viruses, and heavy metals.
Materials Today Chemistry 2021, 22, 100548 and some other works soon-to-be-published
Ceramics additive manufacturing (including colloidal processing)
(Research line led by Mario Borlaf)
Stereolithography (SLA) based techniques such as Digital Light Processing (DLP) consist in using photosensitised monomer solutions filled with ceramic powder to build up layered structures. During the process, certain areas are exposed to light of a certain wavelength to induce polymerisation, and thus solidify on a movable stage. Afterwards, the stage moves, and the process is repeated, stacking the layer on the one generated previously, until the part is completely printed. Subsequently, the green body is heat treated to remove the organic binders and obtaining the densified ceramic part. For high quality pieces, a good colloidal processing is mandatory. This processing is even more evident when an UV-curable system is used because if the raw material is not properly dispersed, the monomer fills the voids between the agglomerates/aggregates of particles, leading into pieces with more defects and with lower density. However, when the powder is properly dispersed and the agglomerates/aggregates are broken, the monomer surrounds the primary particles and when the polymerisation occurs, the piece will be more compact, which results in a higher density piece with less defects after thermal treatment.
J. Power Sources 2023, 570, 233063.
Open Ceramics 2021, 5 100066.
J. Eur. Ceram. Soc. 2020, 40 (4) 1574-1581.
J. Eur. Ceram. Soc. 2019, 39 (13) 3797-3803.
Generation of new photocatalyst materials in the design of artificial photoelectrocatalytic leaves for water remediation, CO2 revalorization and green H2 production
(Research line led by Sonia Bruña)
Provisions of drinking water and of clean and renewable energies to satisfy the growing human demands in the 21st century are increasing problems worldwide and, at the same time, constitute two of the key challenges to sustain the present global social and economic model. In an attempt to contribute to these challenges, we propose a Nature-based strategy (natural systems or processes used to help achieve social goals), in particular a photosynthesis-based solution.
We are working on the design and synthesis of new covalent organic frameworks (COFs) including nitrogen-rich rigid extended aromatic regions and ferrocenyl units, and of organo-sulfur polymers (POSs), to create a library of materials with high activities for light-mediated transformations. These photoanode catalysts will be tested first in photocatalysis and then they will be combined with conventional electrocatalysts (based on Pt or Ni) at the cathode, creating artificial leaves (D). Artificial photoelectrocatalitic leaves, which combine heterogeneous photocatalysis and electrocatalysis principles (minimizing the disadvantages and maximizing the advantages of both technologies), mimic the natural photosynthesis in which photogenerated holes (or electrons) migrate to the anode (or cathode) surface to participate in the water oxidation (or reduction) reaction. The activity of such photoelectrocatalytic leaves might be applied to the inactivation of different kind of water pollutants (organic molecules and heavy metals), to green hydrogen production, to CO2 revalorization, or to simultaneously perform two of these processes, in a double environmental benefit approach.
Hydrogen generation
(Research line led by Rubén Mas-Ballesté)
Current energy needs make a radical change in the way energy is obtained and stored more urgent than ever. To this respect, hydrogen is considered a very promising energy vector. However, hydrogen production through an efficient and green methodology is still a challenge. For this reason, in the group we expend some of our research efforts to develop new materials able to facilitate hydrogen generation through water splitting. This goal is addressed from different perspectives: we investigate photocatalytic and electro-catalytic materials to perform hydrogen evolution reaction and its counterpart in water splitting, i. e. oxygen evolution. In a first approach, we investigated the use of oxidized carbon microfibers and their functionalization with metal nanoparticles is electro-catalytic systems. In a further development, we are now interested on photocatalytic reticular organic materials for artificial photosynthesis.
Dalton Transactions, 2020, 49 (19), 6446-6456.
Catalysis Science & Technology ,2020, 10 (14), 4513-4521.
European Journal of Inorganic Chemistry 2019 (15), 2071-2077.
Chemistry–A European Journal, 2018, 24 (13), 3305-3313.
Ferrocene derivatives as electroactive sensors
(Research line led by Sonia Bruña)
Electroactive sensors provide a low-cost and convenient solution for the detection of variable analytes, mainly due to their low detection limits. We are interested in obtaining ferrocenyl-containing molecules (ferrocene can be reversible oxidized into ferrocenium at a low potential) for acting as electroactive sensors of cations and anions of interest. We have seen that silanediols and disiloxanediols containing ferrocene units act as anionic electroactive sensors (A), capable of selectively recognizing biologically important anions, such as chloride and acetate, present in submillimolar concentrations.
We are also involved in preparing ferrocenyl-containing macromolecules to modify electrode surfaces, resulting in detectable electroactive films for acting as sensors. The presence of sulfur atoms in the macromolecules allows the preparation of Au and Pt electrodes modified by chemisorption, simply by immersing the working electrode in the corresponding electroactive compound solution. To introduce the sulfur atom, we are investigating thiol-ene and thiol-ine reactions (addition of a S-H bond to unsaturated C=C or CºC bonds). Because of its facile nature and efficient and robust characteristics, these coupling reactions have been included into the category of Click Chemistry (a class of simple, atom-economy reactions commonly used for joining two molecular entities of choice). We have investigated different ferrocene derivatives, and ferrocene-containing vinylsilanes, with internal and external double and triple CC bonds against a variety of thiols. Oxathiacrown macrocycles and linear oligo-oxathioethers containing ferrocenyl units, and Si, O, and S atoms, can be prepared following this method. The films prepared by electrode modification with thioether groups are very stable. Interestingly, electroactive sila-oxathioacrown macrocycles act as selective electrochemical sensors of pollutant cations, such as Hg2+ (B).
Dalton Transactions, 2022, 51, 15412-15424.
Organometallics, 2016, 35, 3507-3519.
Macromolecules, 2015, 48, 6955-6969.
