Catalytic applications of recent and improved covalent organic frameworks

Covalent organic frameworks (COFs) are porous crystalline materials that have emerged as promising molecular materials in optoelectronic, catalysis, and gas storage applications. COFs exhibit unique features such as adaptability for various substrates, high chemical stability, tunability, ease of working, and recyclability that render them efficient catalysts. The current mini-review article discusses the synthesis and applications of COFs as catalysts. We hope that the present review will be highly beneficial for researchers working in the area of COFs and their applications in catalysis.

Dihydrobenzofurans and Propynylthiophenes From the Roots of Eupatorium heterophyllum

Seven new dihydrobenzofurans and 2 new propynyl thiophenes were isolated from the roots of Eupatorium heterophyllum together with 13 known compounds. The compounds were characterized using spectroscopic methods including 2D NMR, infrared, and mass spectrometric techniques. Aerial parts of this plant have been known to contain various sesquiterpenoids and displayed high chemical diversity (several compounds isolated and/or identified) among their chemical constituents depending on the collection site. Nevertheless, we found that the chemical diversity in the roots was lower than in the aerial parts.

Metal-Hydrogen-Pi-Bonded Organic Frameworks

We report the synthesis and characterization of a new series of permanently porous, three-dimensional metal-organic frameworks (MOFs), M-HAF-2 (M= Fe, Ga or In), constructed from tetratopic, hydroxamate-based, chelating linkers. The structure of M-HAF-2 was determined by three-dimensional electron diffraction (3DED), revealing a unique interpenetrated hcb-a net topology. This unusual topology is enabled by the presence of free hydroxamate groups, which lead to the formation of a diverse network of cooperative interactions comprising single metal-hydroxamate nodes, staggered π–π interactions between linkers and H-bonding interactions between metal-coordinated and free hydroxamate groups. Such extensive, multimodal interconnectivity is reminiscent of the complex noncovalent interaction networks of proteins and endows M-HAF-2 frameworks with good thermal and exceptionally high chemical stability and allows them to readily undergo post-synthetic metal exchange (PSE). We demonstrate that M-HAF-2 can serve as versatile porous materials for ionic separations, likely aided by one-dimensional channels lined by continuously π-stacked aromatic groups and H-bonding hydroxamate functionalities. As a new addition to the small group of hydroxamate-based MOFs, M-HAF-2 represents a structural merger between MOFs and hydrogen-bonded organic frameworks (HOFs).

The use of 19F in Medicine in Poland and in the World

Fluorine is a chemical element belonging to the group of halogens. Due to its many properties, it has been used in various fields of medicine, mainly in dentistry, pharmacology, oncology, and radiology. It is an element that occurs naturally in the environment with a very high chemical activity. In addition, it has a high affinity for calcium or magnesium [1], which may have a large impact on the body's functioning when a higher dose of fluoride is taken. Moreover, fluorine is an element that has toxic effects, not only on living organisms but also on the environment. Fluoride-based preparations are widely used in several areas of medicine. This paper presents the use of fluoride in its various branches of medicine.

Simulating the impact of piers on hydrodynamics and pollutant transport: A case study in the Middle Yangtze River

It is known that channel engineering, including the construction of piers, will change the river hydrodynamic characteristics, which is a significant factor affecting the transport process of pollutants. With this regard, this study uses the well-validated and tested hydrodynamic module and transport module of MIKE 21 to simulate the hydrodynamics and water quality under various pier densities in the Wuhan reach. Hydrodynamic changes around the piers show spatial differences, which are similar under different discharges. The range and amplitude of hydrodynamic spatial variations increase with the increase in pier density. However, there is a critical value of 1.25 to 2.5 units/km. When the pier density is less than this critical value, this type of cumulative effect is the most significant. Additionally, greater changes can be found in chemical oxygen demand concentrations, which also show spatial and temporal variations. The area with high chemical oxygen demand concentration upstream and downstream from the engineering area exhibits the distribution characteristics of “decrease in the downstream area and increase in the upstream area” and “increase in downstream the area and decrease in the upstream area” respectively. In the reach section of the engineering area, the area with high chemical oxygen demand concentration increases in the front area near the piers and decreases near the shoreline. Furthermore, the concentration shows attenuation actions with a longer residence time owing to the buffering effect of pier groups. These results have significant implications on shoreline planning and utilization. Moreover, they provide scientific guidelines for water management.