Single-Atom Catalysis in Organic Synthesis

Single-atom catalysts hold the potential to significantly impact the chemical sector, pushing the boundaries of catalysis in new, uncharted directions. These materials, featuring isolated metal species ligated on solid supports, can exist in many coordination environments, all of which have shown important functions in specific transformations. Their emergence has also provided exciting opportunities for mimicking metalloenzymes and bridging the gap between homogeneous and heterogeneous catalysis. This review outlines the impressive progress made in recent years regarding the use of single-atom catalysts in organic synthesis. We also illustrate potential knowledge gaps in the search for more sustainable, earth-abundant single-atom catalysts for synthetic applications

Structural Effects of Metal Single-Atom Catalysts for Enhanced Photocatalytic Degradation of Gemfibrozil

The development of efficient catalysts is a highly necessary but challenging task within the field of environmental water remediation. Single-atom catalysts are promising nanomaterials within this respect, but in-depth studies encompassing this class of catalysts remain elusive. In this work, we systematically study the degradation of gemfibrozil, a persistent pollutant, on a series of carbon nitride photocatalysts, investigating both the effect of (i) catalyst textural properties and (ii) metal single atoms on the contaminant degradation. Tests in the absence of the catalyst result in negligible degradation rates, confirming the stability of the contaminant when dispersed in water. Then, photocatalytic tests at optimal pH, solvent, and wavelength reveal a correlation between the support surface area and the degradation. This points to the role of carbon nitride surface nanostructure on gemfibrozil degradation. In particular, the use of silver on mesoporous carbon nitride single-atom catalyst (Ag@mpgC(3)N(4)) leads to an unprecedented degradation of gemfibrozil (>90% within 60 min). The possible degradation intermediates and products were identified by mass spectrometry and were inert by cytotoxicity evaluation. We anticipate that, with further refinement and customization, the carbon nitride catalysts reported herein may find broad applications for light-driven degradation of other contaminants of emerging concern

Nanostructured Carbon Nitride for Continuous-Flow Trifluoromethylation of (Hetero)arenes

Efficient catalytic methods for the trifluoromethy-lation of (hetero)arenes are of particular importance in organic and pharmaceutical manufacturing. However, many existing protocols rely on toxic reagents and expensive or sterically hindered homogeneous catalysts. One promising alternative to conduct this transformation involves the use of carbon nitride, a non-toxic photocatalyst prepared from inexpensive precursors. Nonetheless, there is still little understanding regarding the interplay between physicochemical features of this photocatalyst and the correspond-ing effects on the reaction rate. In this work, we elucidate the role of carbon nitride nanostructuring on the catalytic performance, understanding the effect of surface area and band gap tuning via metal insertion. Our findings provide new insights into the structure-function relationships of the catalyst, which we exploit to design a continuous-flow process that maximizes catalyst-light interaction, facilitates catalyst reusability, and enables intensified reaction scale-up. This is particularly significant given that photocatalyzed batch protocols often face challenges during industrial exploitation. Finally, we extrapolate the rapid and simplified continuous-flow method to the synthesis of a variety of functionalized heteroaromatics, which have numerous applications in the pharmaceutical and fine chemical industries

Trabajo profesional y conflicto trabajo-escuela en estudiantes-trabajadores: El papel mediador de distanciamiento psicológico del trabajo

In recent years there Portuguese higher education institutions have been aiming to attract more people to the educational system that are either in the labor market by offering evening and weekend graduate academic programs. Blending work and school is a demanding task and, so far, at the country level this phenomenon has received relatively little empirical attention. The purpose of the study is to build on existing work-to-school conflict literature and to explore a possible relationship between professional work load on work-to-school conflicts among working students enrolled in a master program. Moreover we test the role of psychological detachment from work as mediator in this process. This model was tested, through path analysis, using 152 working students, 88 women and 64 men, enrolled as fulltime students in evening and weekend master programs.. The model showed an adequate fit to the data, suggesting that the influence of professional work load on work-to-school conflict is fully mediated by psychological detachment from work. These findings unveil a new perspective on working students enrolled in postgraduate school, pointing out the importance of psychological detachment from work to a better understand the impact of blending work and school. Contributions to the work-school literature, future research directions, and limitations of the study are discussed. En los últimos años, las instituciones de enseñanza superior portuguesas han intentado atraer a más personas al sistema educativo que se encuentran en el mercado laboral ofreciendo programas académicos de posgrado nocturnos y de fin de semana. La combinación del trabajo y la escuela es una tarea exigente y, hasta ahora, a nivel de país este fenómeno ha recibido relativamente poca atención empírica. El propósito del estudio es basarse en la literatura sobre conflictos de trabajo a escuela existentes y explorar una posible relación entre la carga de trabajo profesional en los conflictos entre el trabajo y la escuela entre los estudiantes que trabajan matriculados en un programa de maestría. Además, probamos el papel del desapego psicológico del trabajo como mediador en este proceso. Este modelo fue probado, a través de análisis de trayectoria, utilizando 152 estudiantes de trabajo, 88 mujeres y 64 hombres, matriculados como estudiantes de tiempo completo en programas de posgrado de tarde y fin de semana. El modelo mostró un ajuste adecuado a los datos, sugiriendo que la influencia de la carga de trabajo profesional en el conflicto entre el trabajo y la escuela está plenamente mediado por el desapego psicológico del trabajo. Estos resultados revelan una nueva perspectiva sobre los estudiantes que trabajan y que frecuentan la escuela de posgrado, señalando la importancia del desapego psicológico del trabajo para comprender mejor el impacto de la mezcla de trabajo y la escuela. Se discuten las contribuciones a la literatura de la escuela de trabajo, las direcciones futuras de la investigación y las limitaciones del estudio

Enhanced flow synthesis of small molecules by in-line integration of sequential catalysis and benchtop twin-column continuous chromatography

We report an improved approach for the integration of flow synthesis and continuous chromatography, for applications in the end-to-end preparation of pharmaceutically-relevant small molecules. It involves the combination of sequential microreactors and twin-column counter-current chromatography based on the often-used C18 columns. The column loading method ensures that the product breaking through a fully loaded first column is loaded onto the second one, avoiding waste of precious material and technological complexity associated with the use of four-to-six columns typical of simulated moving bed chromatography. The system was applied to synthesize biphenyl via Suzuki–Miyaura reaction, and was also demonstrated for other structurally-different compounds. Compared to the discontinuous and other traditional approaches, our method leads to higher isolated yields (ca. +60%), higher productivity (ca. +30%), and reduced solvent consumption (ca. −80%). A circularity and life-cycle analysis was also conducted to demonstrate the environmental benefits of the flow process

An earth-abundant Ni-based single-atom catalyst for selective photodegradation of pollutants

Highly efficient catalytic technologies are urgently needed to remove pharmaceutical pollutants from water. In this work, the preparation, characterization, and photocatalytic performance of an earth-abundant Ni-based heterogeneous catalyst featuring highly dispersed Ni species over nanosheets of carbon nitride are reported. The absence of any metallic nickel phase has been confirmed by spectrometric analyses, unveiling the Ni-N environment for the metal centers and attaining synergistic interfacial carrier transfer via N-Ni-N coordination. By combining advanced characterizations with kinetic investigations, it is demonstrated that these newly formed isolated single atoms of Ni act as a bridge, facilitating faster electron transfer, increasing the charge density on Ni, and reducing the photocarrier transfer barrier. Compared to literature precedents, this substantially enhances the degradation of gemfibrozil, a model pharmaceutical pollutant found in wastewater, reducing the formation of toxic benzenic byproducts during photooxidation. This effect, which is not observed over conventional nanoparticle-based materials, discriminates the role of single-atom and nanoparticle-based catalysis during degradation of pollutants. This work opens new avenues in designing selective and earth-abundant photocatalysts for advanced oxidation processes, showing the importance of atom coordination to control the surface and catalytic properties of single-atom materials.Web of Science57art. no. 210017

Hierarchical Y and USY zeolites designed by post-synthetic strategies

ISSN:1616-3028ISSN:1616-301

Mesopore Formation in USY and Beta Zeolites by Base Leaching: Selection Criteria and Optimization of Pore-Directing Agents

ISSN:1528-7483ISSN:1528-750