Understanding the Roles of Thiophenol-Ligated Ag-Based Nanoclusters on TiO2 during the Catalytic Hydrogenation of Nitroarenes.

Elucidating the correlations between the core structure of atomically precise nanoclusters and their catalytic activities is fundamentalfor exploring highly efficient nanocatalysts. Herein, a series of Ag-based nanoclusters protected by 2,4-dimethylphenylthiophenol (specifically Ag4Pd2(SPhMe2)8 and Ag24M(SPhMe2)18 where M = Ag, Pd, and Pt) were synthesized and deposited on TiO2 supports as heterogeneous catalysts for the selective hydrogenation of nitroarenes with NaBH4 as the reductant. It was found that Ag4Pd2(SPhMe2)8 could spontaneously lose its ligands during catalysis, leading to the formation of polydispersed AgPd nanoparticles. This transformation endows the system with extraordinary activity for driving the hydrogenation of nitroarenes. However, the Ag24M (M = Ag, Pd, and Pt) systems, maintain their core structures during catalysis. They follow the generally reported ligand-mediated hydride-involved process, with catalytic activities depending on the central atom (Pt > Pd > Ag), which affects the hydride transferred from the nanoclusters to the reactant to regulate the catalysis.

Insight to the Catalytic Activity of Atomically Precise Ag4Ni2 Nanoclusters on Silicon Carbide for Nitroarene Reduction.

Atomically precise Ag4Ni2 nanoclusters with 2,4-dimethylbenzenethiol as the ligands were synthesized and characterized as a cocatalyst of SiC for the selective hydrogenation of nitroarenes to arylamine in the presence of NaBH4. The obtained Ag4Ni2/SiC samples exhibited extraordinary catalytic activity, and a self-accelerated catalytic process was observed with the reduction of nitrophenol to aminophenol as the model reaction. Experimental comparison between the Ag4Ni2/SiC samples before and after the catalysis showed that the transformation of Ag4Ni2 clusters to polydisperse Ag particles as well as amorphous NiOx on the surface of SiC in the catalysis was the key to their high activity. AIMD calculations revealed that the transformation of Ag4Ni2 was driven by the presence of multiple hydrides on the cluster, which induced the detachment of the thiol ligand of the nanoclusters.

Direct Z-scheme system of UiO-66 cubes wrapped with Zn0.5Cd0.5S nanoparticles for photocatalytic hydrogen generation synchronized with organic pollutant degradation.

Optimized fabrication of Z-scheme photocatalyst based on MOF materials offers sustainable energy generation and environmental improvement due to their attractive properties. The Z-scheme heterojunctions consisting of UiO-66 cubes covered with Zn0.5Cd0.5S nanoparticles were fabricated by a facile solvothermal method. Thanks to the Z-scheme carrier transport under simulated sunlight irradiation, UiO-66@Zn0.5Cd0.5S exhibited enhanced photocatalytic performance of H2 generation synchronized with organic pollutant degradation in fluoroquinolone antibiotic wastewater. Synergistically, the highest comprehensive performance was obtained in ciprofloxacin solution. The H2 yield reached 224 µmol∙ g-1∙ h-1 and simultaneously the removal efficiency was up to 83.6 %. The degradation pathways revealed that the process of piperazine ring cleavage and decarboxylation also generates H protons, further promoting the production of H2. Therefore, the effective spatial separation and transfer of the photoinduced carriers are attributed to the good band structure, large specific surface area, and cooperative reduction and oxidation reactions of UiO-66@Zn0.5Cd0.5S, resulting in significant photocatalytic activity. The toxicity assessment of antibiotics and intermediate products during the photocatalytic reaction also verifies the reduction of environmental risk. This study highlights a promising way to expand the application of the MOFs-based photocatalyst in clean energy conversion coupling with water remediation.

12.7 W intra-cavity pumped Ho:YAG laser with near-diffraction-limited beam quality.

We demonstrated a compact and efficient Ho:YAG slab laser intra-cavity pumped by a Tm:YLF slab laser for the first time. In the Tm:YLF laser operation, the maximum power of 32.1 W with optical-to-optical efficiency of 52.8% was obtained. In the intra-cavity pumped Ho:YAG laser operation, the output power of 12.7 W at 2122 nm was obtained. The beam quality factors M2 in the vertical and horizontal directions were 1.22 and 1.11, respectively. The RMS instability was measured to be lower than 0.1%. To the best of our knowledge, this was the maximum power for the Tm-doped laser intra-cavity pumped Ho-doped laser with near-diffraction-limited beam quality.

A novel slag composite for the adsorption of heavy metals: Preparation, characterization and mechanisms.

The utilization of solid waste for resource recovery and production of value-added products is the theme of green chemistry. Currently, how to using solid wastes to prepare environmentally-functional materials with high performance and strength is one of the hot topics. In this research, electrolytic manganese residue (EMR) was thermally activated with calcite to prepare a silicon-based functionalized adsorbent (C-EMR) for the removal of cadmium (Cd2+, 467.14 mg/g) and lead (Pb2+, 972 mg/g). The thermodynamic results indicated that the removal process of Cd2+ and Pb2+ by C-EMR were endothermic and spontaneous. HNO3 can effectively strip the two adsorbed metals from C-EMR with the stripping efficiency of nearly 80% for Cd2+ and 99.92% for Pb2+, indicating that adsorption and ion exchange may be the main reason for the removal of the metals on C-EMR. Besides, surface precipitation was also responsible for removing some Pb2+ from the aquatic environment according to the X-ray photoelectron spectrometry (XPS) analysis. Results indicate that -SiO3- has stronger affinity with Pb2+ and Cd2+ than other groups ((-MnO2), -OH) by theoretical calculation (VASP, GGA-PBE). This study shows that this novel adsorbent (C-EMR) can be adopted as an environmentally-friendly, inexpensive and efficient adsorbent for removal of Cd2+ and Pb2+ from aquatic solution. This technique not only provides potential adsorbent for the elimination of heavy metals but also proposes an alternative route for the treatment and utilization of waste solid.

New potential of boron-based COFs: the biocompatible COF-1 for reactive oxygen generation and antimicrobial applications.

Photocatalytic covalent organic frameworks (COFs) are popular in the field of biomedical materials and also have potential as antimicrobial materials. Herein, a boron-based COF was used in antibacterial applications innovatively. The results of this study suggested that COF-1, the earliest boroxine COF, could produce a variety of reactive oxygen species (ROS) under visible light irradiation. In order to explore more applications of COF-1, antibacterial tests were carried out based on the above results. The test results showed that the material displayed an obvious bactericidal effect on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) by releasing ROS under white light. According to the results of plate coating, all bacteria died after co-cultivation with COF-1 under white light for about 120 minutes. In a word, this study could provide a new idea for the application of boron-based COFs as multifunctional photocatalysts in future.

Preparation of functional material layers of TT-COFs with built-in formyl groups for efficient dyes removal.

There is no doubt that the wide application of COFs depends on the diversity and complexity of their structure and composition, as well as the feasibility and convenience of use. Herein, large area defect-free continuous functional material layers have been fabricated by compounding sub-stoichiometric tetratopic-tritopic covalent organic frameworks (TT-COFs) on graphene oxide (GO) via simply hot pressing. The one-step synthesis of TT-COFs with built-in formyl groups endowed the robust material layers with extraordinary host-guest interactions, so they can specifically reject cations dyes according to adsorption effect, molecular sieving and Donnan effect. Owing to the through-plane molecular transfer channels, large amounts of water molecules can pass through the internal channel rapidly. As a result, high rejection of 99.5% and large flux of 309.99 L·m-2·h-1·bar-1 for dye molecules have been realized. This simple and effective method provided more extensive practicality and greater convenience in recycling and reuse, and demonstrated the utility and high efficiency of TT-COFs with built-in formyl groups as an advanced material platform for dyes removal.

A Versatile Method for Functionalization of Covalent Organic Frameworks via Suzuki-Miyaura Cross-Coupling.

Post-synthetic modification (PSM) is a prevalent and powerful strategy to introduce desired functionalities into covalent organic frameworks (COFs) for functional products, expediting their applications vastly. Herein, we demonstrate a PSM strategy for functionalizing brominated COFs via the well-developed Suzuki-Miyaura cross-coupling. By this, a variety of functionalities were installed into COFs efficiently, while the crystallinity and porosity of COFs was well-retained. As a proof-of-concept, BrCOF-2 was modified with trifluoromethyl groups to produce a SF6 adsorbent with remarkably enhanced properties. This facile and versatile approach opens a new door for the synthesis of functional COFs, and greatly expands the scope of their structural design aiming for various properties and applications.