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The preparation of ultra–small silver nanoparticles (average diameter ≤10 nm) is a technical problem because of their aggregation tendency. Therefore, the preparation conditions are usually harsh and complex. It is widely recognized that covalent organic frameworks (COFs) represent a novel class of porous crystalline compounds with broad applications in various fields. In this work, an environmentally and economically friendly new method has been developed for synthesizing ultra–small silver nanoparticles by reducing silver ions in ethanol solution with a covalent organic framework (TPB–DMTP–COF) as a template and reductant at room temperature. Interestingly, the TPB–DMTP–COF not only serves as a template and reductant but also functions as a stabilizer. Moreover, the TPB–DMTP–COF can be utilized repeatedly as a reductant. The morphology and structure of the silver nanoparticles were examined using transmission electron microscopy and showed that they were spherical with an average particle size of approximately 7.5 nm. Compared with the previously reported silver nanoparticles, the silver nanoparticles synthesized by this new method are not coated with Surfactant, such as Polyvinylpyrrolidone (PVP). As a result, they possess a larger exposed surface area, exhibit increased activity, and demonstrate excellent antimicrobial properties against both Gram–negative Escherichia coli and Gram–positive bacteria Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

It is well known that hydrogen promotes catalyst activity in Cr/PNP‐catalyzed ethylene tetramerization, but the mechanism of this effect is unclear. A density functional theory (DFT) study was conducted to explore this effect, and conformation changes were carefully taken into consideration to build a clear reaction pathway. Three components in the ethylene tetramerization catalytic cycle were examined in detail: the production of 1‐hexene from metallacycloheptane, the production of 1‐octene from metallacyclononane, and the formation of an active centre on the Cr/PNP catalyst. This result indicates that the formation of an active centre on the catalyst becomes more favorable upon the imposition of hydrogen, where hydrogen functions as a second ligand. This easing effect could be the key factor leading to the outperformed Cr/PNP catalyst activity in ethylene tetramerization. [ABSTRACT FROM AUTHOR]