Ti-Containing Mesoporous Organosilica as a Photocatalyst for Selective Olefin Epoxidation

Yolk-shell structured magnetic mesoporous organosilica supported ionic liquid/Cu complex: an efficient nanocatalyst for the green synthesis of pyranopyrazoles

The preparation of yolk-shell structured magnetic mesoporous composites is a significant subject between researchers. Especially, modification of theses composites with ionic liquid/metal complex is very important for catalytic processes. In the present study, a novel magnetic methylene-based periodic mesoporous organosilica (PMO)-supported ionic liquid/Cu complex with yolk-shell structure (YS-Fe3O4@PMO/IL-Cu) was prepared via the soft template-assisted method. The TGA, FT-IR, SEM, EDX, XRD, VSM, nitrogen-sorption, and ICP techniques were employed to identify YS-Fe3O4@PMO/IL-Cu. The YS-Fe3O4@PMO/IL-Cu material was applied as a powerful nanocatalyst for the synthesis of pyranopyrazoles under ultrasonic media. The study demonstrated that the YS-Fe3O4@PMO/IL-Cu nanocatalyst is highly recyclable, selective, and effective. The leaching test was performed to investigate the nature of the designed catalyst under the applied conditions.

Photocatalyzed Transformation of Free Carbohydrates

In the growing context of sustainable chemistry, one of the challenges of organic chemists is to develop efficient and environmentally friendly methods for the synthesis of high-added-value products. Heterogeneous photocatalytic transformations have brought revolution in this regard, as they take advantage of an unlimited source of energy (solar light) or artificial UV light to onset organic chemical modifications. The abundance of free carbohydrates as chemical platform feedstock offers a great opportunity to obtain a variety of industrial interest compounds from biomass. Due to their chirality and polyfunctionality, the conversion of sugars generally requires multi-step protocols with protection/deprotection steps and hazardous chemical needs. In this context, several selective and eco-friendly methodologies are currently under development. This review presents a state of art of the recent accomplishments concerning the use of photocatalysts for the transformation and valorization of free carbohydrates. It discusses the approaches leading to the selective oxidation of free sugars, their degradation into organic chemicals, or their use for hydrogen production.

Recent advances in hybrid periodic mesostructured organosilica materials: opportunities from fundamental to biomedical applications

Periodic mesoporous organosilica nanostructures functionalized with various active functional groups: from design to biomedical applications.

Heterogeneous photocatalytic nanomaterials: prospects and challenges in selective transformations of biomass-derived compounds

Heterogeneous photocatalysis has become a comprehensively studied area of research during the past three decades due to its practical interest in applications including water-air depollution, cancer therapy, sterilization, artificial photosynthesis (CO2 photoreduction), anti-fogging surfaces, heat transfer and heat dissipation, anticorrosion, lithography, photochromism, solar chemicals production and many others. The utilization of solar irradiation to supply energy or to initiate chemical reactions is already an established idea. Excited electron-hole pairs are generated upon light irradiation of a wide-band gap semiconductor which can be applied to solar cells to generate electricity or in chemical processes to create/degrade specific compounds. While the field of heterogeneous photocatalysis for pollutant abatement and mineralisation of contaminants has been extensively investigated, a new research avenue related to the selective valorisation of residues has recently emerged as a promising alternative to utilise solar light for the production of valuable chemicals and fuels. This tutorial review will focus on the potential and applications of solid photonanocatalysts for the selective transformation of biomass-derived substrates.

High-value chemicals obtained from selective photo-oxidation of glucose in the presence of nanostructured titanium photocatalysts

Glucose was oxidized in the presence of powdered TiO(2) photocatalysts synthesized by an ultrasound-promoted sol-gel method. The catalysts were more selective towards glucaric acid, gluconic acid and arabitol (total selectivity approx. 70%) than the most popular photocatalyst, Degussa P-25. The photocatalytic systems worked at mild reaction conditions: 30°C, atmospheric pressure and very short reaction time (e.g. 5 min). Such relatively good selectivity towards high-valued molecules are attributed to the physico-chemical properties (e.g. high specific surface area, nanostructured anatase phase, and visible light absorption) of novel TiO(2) materials and the reaction conditions. The TiO(2) photocatalysts have potential for water purification and energy production and for use in the pharmaceutical, food, perfume and fuel industries.

Hydroxyl species in large-pore phenylene-bridged periodic mesoporous organosilica

Silanol species in phenylene-bridged periodic mesoporous organosilica (PMO), templated via tri-block copolymer Pluronic P123 and thus characterized by large pores and amorphous wall structure, have been characterized by means of FT-IR spectroscopy. Investigation has been carried out on both the naked sample outgassed at different temperatures and the sample when interacting with molecular probes able to form H-bonding (ammonia and carbon monoxide). After outgassing at 773 K, the material shows both isolated silanols and silanols engaged in "intraframework" H-bonding with the pi-cloud of structural aromatic rings. Interaction with ammonia showed that a fraction of these species is inaccessible, being probably located inside the pore walls. Thermal treatment above 673 K causes the appearance of SiO3(OH) species formed as a consequence of the cleavage of some Si-C bonds. The presence of hydroxyls slightly more acidic than isolated silanols has been evidenced: these are interpreted as perturbed geminal species.

A Fluorescent Molecular Switch Driven by the Input Sequence of Metal Cations: An Azamacrocyclic Ligand Containing Bipolar Anthracene Fragments

An azamacrocyclic ligand (L) containing two anthracene (AN) fragments connected through two triethylenetetramine bridges has been synthesized, in which each of the bridges can coordinate with one metal cation. The effects of pH and metal cations (Zn2+ and Cd2+) on the emission properties of L were studied in water. Without metal cations, L does not show any emission at basic pH values. The addition of Zn2+ leads to the production of excimer emission, which is due to a static excimer formed by direct excitation of the intramolecular ground-state dimer of the bipolar AN fragments that approach each other by Zn2+ binding. In contrast, Cd2+ addition does not result in excimer emission because the Cd2+-AN pi complex, formed by donation of a pi electron of the AN fragments to the adjacent Cd2+, suppresses pi-stacking interactions of the AN fragments. The most notable feature is the appearance of excimer emission controlled by the input sequence of metal cations: Zn2+-->Cd2+ sequential addition (each one equivalent) allows excimer emission, whereas the reverse sequence (Cd2+-->Zn2+) does not. In the Zn2+-->Cd2+ sequence, Cd2+ coordination is structurally restricted by the first Zn2+ coordination with the other polyamine bridge, leading to the formation of a weak Cd2+-AN pi complex. In contrast, for the reverse sequence, the first Cd2+ coordination forms a stable Cd2+-AN pi complex, which is not weakened by sequential Zn2+ coordination, resulting in no excimer emission.

Encapsulation of titanium(iv) oxide particles in hollow silica for size-selective photocatalytic reactions

A core-shell composite of TiO2 particles encapsulated in a hollow silica was fabricated, and the core-shell composite showed size-selective photocatalytic activity for decomposition of organics without reducing the intrinsic activity of the naked TiO2 core.