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A fluorescent covalent organic framework (COF), featuring precise distribution of thioether pendant arms inside the cavity, was designed. The thioether-functionalized COF exhibits selective sensing and capture of Au ions at ultra-trace levels in water with high sensitivity, selectivity and adsorption capacity, which makes it an excellent candidate for selective detection and recovery of Au. [ABSTRACT FROM AUTHOR]

Development of visible-light-induced and rapid water disinfection is of significant importance. Covalent triazine-based frameworks (CTFs) with pre-designable structures and favorable semiconductive behaviors hold great promise for photocatalytic water disinfection. Here, we report an Ag/AgBr/CTF composite with a layered structure, which serves as an efficient photocatalyst for rapid water disinfection. Water disinfection with ＞99.99% inactivation of Escherichia coli within 12 min was achieved by using a small amount of Ag/AgBr/CTF under visible light irradiation. The inactivation efficiency of Ag/AgBr/CTF was ∼10 times better than that of bare Ag/AgBr. Rapid water disinfection by the Ag/AgBr/CTF composite mainly results from the greatly improved generation of reactive oxygen species through the synergistic effects among the three components and the affinity of CTF to the cell wall of bacteria. [ABSTRACT FROM AUTHOR]

Despite extensive efforts dedicated to researching two-dimensional (2D) transition metal oxides (TMOs), significant challenges still remain to simplify their synthesis and improve the activity and reusability of these materials. In this work, we prepared a 2D Cu-containing layered double oxide (CuLDO) under mild conditions. Only via stirring LDO in diluted Cu solution at room temperature could ion exchange between Mg in LDO and Cu ions from that solution allow fixing of Cu onto the surfaces of LDO nanosheets with good dispersion at a high density. The obtained CuLDO was then annealed to give CuOx-rich nanosheets (denoted as c-CuLDO), which maintained a thin thickness of 5–9 nm with a flowers-like architecture thanks to the structural memory of the source materials. The excellent morphology of CuOx-based nanosheets helped to avoid the restacking of nanosheets. Such a c-CuLDO outperformed many other reported Cu-based nanomaterials as a catalyst in phenol degradation (k = 0.335 min−1) because c-CuLDO could efficiently activate persulfate to generate abundant amounts of sulfate radical (SO4Ṗ−). Furthermore, the catalytic activity of used c-CuLDO could be restored by a simple hydrothermal treatment. The developed chemistry could also be used to remove copper ions from wastewater, generating value-added Cu-based nanomaterials and eliminating waste at the same time. The current results may inspire the design of novel low dimensional nanomaterials that are difficult to synthesize directly by conventional bottom-up strategies. [ABSTRACT FROM AUTHOR]

Monolayer Bi2MoO6 nanosheets have been successfully prepared for the first time via a bottom-top approach with surfactant assistance, and show 8 times higher activity than bulk Bi2MoO6 for the selective oxidation of benzyl alcohol. Ultrafast charge separation and more acid–base active sites on the monolayer nanosheets are considered to be responsible for the robust photoactivity. [ABSTRACT FROM AUTHOR]

Here, we show for the first time that the photocatalytic activity of covalent triazine-based frameworks (CTFs) can be efficiently improved using a facile sulfur-doping approach. The sulfur-doped CTFs show superior photocatalytic activity and stability in hydrogen evolution from water under visible light irradiation over pristine CTFs and g-C3N4. The significantly improved catalytic efficiency was attributed to sulfur-doping in the frameworks, which results in enhanced adsorption of visible light, reduced recombination of free charge carriers, and rapid separation and transportation of photogenerated electron–holes. [ABSTRACT FROM AUTHOR]

A hydrophobic palladium complex of the chelating N-heterocyclic dicarbene (NHDC) (3) was synthesized through in situdeprotonation of a bisimidazolium salt (2) by Pd(OAc)2in DMSO, subsequent basic hydrolysis and acidification resulted in the formation of four NHDC palladium complexes bearing carboxylic functional groups (4–7). Complexes 4–7are air-stable, pH-responsive and water-soluble under basic conditions due to deprotonation of the carboxylic groups. The catalytic activities of the hydrophilic catalytic systems from 4–7were preliminarily evaluated using the Suzuki–Miyaura cross-coupling reaction in pure water, high catalytic activity and chemical selectivity were observed in comparison with their hydrophobic analogue from 3. Either the catalytic aqueous solution or the pH-responsive catalysts were easily separated and could be recycled at least four times. TEM analysis revealed that Pd(0) nanoparticles were formed after the catalytic reaction. [ABSTRACT FROM AUTHOR]

An ammonium-functionalized water-soluble bidentate nitrogen-containing ligand (3) and its palladium chelating complex (4) have been easily prepared from the commercial available starting materials in high overall yields. The charge distributions and molecular orbital analyses of 3, 4and non-ionic hydrophobic analogue (2a) based on the optimized structures were implemented. The crystal structure of 4has been established by single-crystal X-ray diffraction. The water-soluble palladium complex was a much more effective catalyst than 2ain palladium-catalyzed Suzuki–Miyaura cross-coupling reaction in air and pure water. High catalytic activity of aryl chlorides and aryl bromides was observed. The mercury drop test, poison experiments and TEM analysis of the catalytic solution showed Pd(0) were involved in catalysis. The palladium nanoparticles of 3.0 ± 0.6 nm were formed after the catalytic reaction, they were stabilized by synergetic effect of coordination and electrostatic interactions from the ammonium-functionalized chelating ligand. No precipitate was observed when the aqueous nanoparticles were stored in air for months. [ABSTRACT FROM AUTHOR]

Selective photoreduction of CO 2 into a given product is a great challenge but desirable. Inspired by natural photosynthesis occurring in hierarchical networks over non-precious molecular metal catalysts, we demonstrate an integration of single Ni sites into the hexagonal pores of polyimide covalent organic frameworks (PI-COFs) for selective photoreduction of CO 2 to CO. The single Ni sites in the hexagonal pores of the COFs serve as active sites for CO 2 activation and conversion, while the PI-COFs not only act as a photosensitizer to generate charge carriers but also exert a promoting effect on the selectivity. The optimized PI-COF with a triazine ring exhibits excellent activity and selectivity. A possible intra- and inter-molecular charge-transfer mechanism was proposed, in which the photogenerated electrons in PI-COFs are efficiently separated from the central ring to the diimide linkage, and then transferred to the single Ni active sites, as evidenced by theoretical calculations., (This journal is © The Royal Society of Chemistry 2020.)

Halogens, as typical non-metal dopants, have attracted intensive interests for developing highly active photocatalysts. However, the essential factors and underlying mechanism of halogen modification are still unclear. Herein, we systematically report the development of halogen (F, Cl and Br)-doped covalent triazine-based frameworks (CTFs) via a facile thermal treatment of CTFs and an excess of ammonium halide. The introduction of halogen atoms endowed CTFs with multiple superior effects such as improved optical absorption, promoted charge migration, narrowed band gaps and tuned band positions. The newly developed halogen-doped CTFs showed remarkable photocatalytic activities for H 2 evolution under visible-light irradiation. Notably, the most enhanced photocatalytic performance was obtained with Cl-doped CTFs, which exhibited 7.1- and 2.4-fold enhancements compared to un-doped CTFs and Cl-doped g-C 3 N 4 , respectively. The electronegativity and atomic radius of the halogen atoms affected the modification of the optical and electronic properties, leading to different photocatalytic performances of F-, Cl- and Br-doped CTFs. The conclusions presented in this work will provide some new insights into the understanding of the doping effect for the improvement of the photocatalytic activity of halogen-doped CTF photocatalysts., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The synthesis of five-membered cyclic carbonates via catalytic cycloaddition reaction of CO 2 with epoxides is considered to be an effective technology for alleviation of the energy crisis and global warming. Various commercial organic bases and ionic salts were used as catalysts, while the relationship of catalytic activity and compound structure has been seldom explored. Herein, a facilely obtained binary catalytic system based on triethylamine/NBu 4 Br was developed for CO 2 activation and chemical fixation. The highly efficient catalytic system showed outstanding conversion and above 99% selectivity under metal-free mild reaction conditions (100 °C, 1 atm) in one hour. The detailed process of CO 2 activation and chemical fixation was investigated at the molecular level by a series of experiments and theoretical calculation, which provided a mode for the design and synthesis of a highly efficient catalytic system for conversion of CO 2 under mild conditions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Monolayer Bi 2 MoO 6 nanosheets have been successfully prepared for the first time via a bottom-top approach with surfactant assistance, and show 8 times higher activity than bulk Bi 2 MoO 6 for the selective oxidation of benzyl alcohol. Ultrafast charge separation and more acid-base active sites on the monolayer nanosheets are considered to be responsible for the robust photoactivity.

The commercially available 2,2'-dipyridylamine was used as a supporting ligand in the palladium-catalyzed Sonogashira cross-coupling reaction. The reactions between aryl iodides and terminal alkynes with different steric hindrance can be efficiently performed in the absence of copper in neat water at room temperature. The superior catalytic performance of the catalytic system was attributed to water solubility of the palladium 2,2'-dipyridylamine complex. Palladium nanoparticles with small size and narrow size distribution were formed after the cross-coupling reaction.