Self-Supported Chiral Dirhodium Organic Frameworks Enables Efficient Asymmetric Cyclopropanation.

The development of heterogeneous chiral dirhodium catalysts for fabricating important bioactive substances and reducing the loss of noble metals has long been of significant interest. However, there still remains formidable synthetic challenges since it requires multiple steps of the synthetic process, and rhodium is easily leached from solid materials during the reaction. Here, we demonstrated a self-supported strategy based on the Suzuki-Miyaura coupling reaction to construct two chiral dirhodium organic frameworks for heterogeneous asymmetric catalysis. The synthetic approach is simple and efficient since it requires only a small number of preparation steps and does not require any catalyst supporting materials. The obtained chiral dirhodium materials can be highly efficient and recyclable heterogeneous catalysts for asymmetric cyclopropanation between diazooxindole and alkenes. Importantly, Rh2-MOCP-2 exhibited almost similar catalytic performance compared to homogeneous catalyst Rh2(S-Br-NTTL)4. The afforded catalytic performance (93.9% yield with 80.9% ee) highly surpasses previous heterogeneous dirhodium catalysts reported to date.

Synergistic oxidation of toluene through bimetal/cordierite monolithic catalysts with ozone.

Toluene treatment has received extensive attention, and ozone synergistic catalytic oxidation was thought to be a potential method to degrade VOCs (violate organic compounds) due to its low reaction temperature and high catalytic efficiency. A series of bimetal/Cord monolithic catalysts were prepared by impregnation with cordierite, including MnxCu5-x/Cord, MnxCo5-x/Cord and CuxCo5-x/Cord (x = 1, 2, 3, 4). Analysis of textural properties, structures and morphology characteristics on the prepared catalysts were conducted to evaluate their performance on toluene conversion. Effects of active component ratio, ozone addition and space velocity on the catalytic oxidation of toluene were investigated. Results showed that MnxCo5-x/Cord was the best among the three bimetal catalysts, and toluene conversion and mineralization rates reached 100 and 96% under the condition of Mn2Co3/Cord with 3.0 g/m3 O3 at the space velocity of 12,000 h-1. Ozone addition in the catalytic oxidation of toluene by MnxCo5-x/Cord could efficiently avoid the 40% reduction of the specific surface area of catalysts, because it could lower the optimal temperature from 300 to 100 °C. (Co/Mn)(Co/Mn)2O4 diffraction peaks in XRD spectra indicated all the four MnxCo1-x/Cord catalysts had a spinel structure, and diffraction peak intensity of spinel reached the largest at the ratio of Mn:Co = 2:3. Toluene conversion rate increased with rising ozone concentration because intermediate products generated by toluene degradation might react with excess ozone to generate free radicals like ·OH, which would improve the toluene mineralization rate of Mn2Co3/Cord catalyst. This study would provide a theoretical support for its industrial application.

CsPbBr3 Quantum Dots Promoted Depolymerization of Oxidized Lignin via Photocatalytic Semi-Hydrogenation/Reduction Strategy.

Due to the demanding depolymerization conditions and limited catalytic efficiency, enhancing lignin valorization remains challenging. Therefore, lowering the bond dissociation energy (BDE) has emerged as a viable strategy for achieving mild yet highly effective cleavage of bonds. In this study, a photocatalytic semi-hydrogenation/reduction strategy utilizing CsPbBr3 quantum dots (CPB-QDs) and Hantzsch ester (HEH2 ) as a synergistic catalytic system was introduced to reduce the BDE of Cß -O-Ar, achieving effective cleavage of the Cß -O-Ar bond. This strategy offers a wide substrate scope encompassing various ß-O-4 model lignin dimers, preoxidized ß-O-4 polymers, and native oxidized lignin, resulting in the production of corresponding ketones and phenols. Notably, this approach attained a turnover frequency (TOF) that is 17 times higher than that of the reported Ir-catalytic system in the photocatalytic depolymerization of the lignin model dimers. It has been observed via meticulous experimentation that HEH2 can be activated by CPB-QDs via single electron transfer (SET), generating HEH2 ⋅+ as a hydrogen donor while also serving as a hole quencher. Moreover, HEH2 ⋅+ readily forms an active transition state with the substrates via hydrogen bonding. Subsequently, the proton-coupled electron transfer (PCET) from HEH2 ⋅+ to the carbonyl group of the substrate generates a Cα ⋅ intermediate.

Adsorption interactions between typical microplastics and enrofloxacin: Relevant contributions to the mechanism.

Microplastics (MPs) are increasingly contaminating the environment and they can combine with antibiotics as carriers to form complex contaminants. In this study, we systematically investigated the interactions between the antibiotic enrofloxacin (ENR) and MPs comprising polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS). Characterization was performed by using conventional techniques and the mechanisms involved in interactions were initially explored based on adsorption kinetics, isotherms, and resolution experiments, and the adsorption capacities of the MPs were determined. In addition, the extended Derjaguin-Landau-Verwey-Overbeek theory was used to investigate the interaction mechanisms. The results showed that the interactions were weaker in strong acidic and alkaline environments, and the interactions were also inhibited at higher salt ion concentrations. The saturation adsorption amounts of ENR on PVC, PE, and PS were 74.63 µg/g, 103.09 µg/g, and 142.86 µg/g, respectively. The interactions between MPs and ENR were dominated by hydrophobic interactions, followed by van der Waals forces and acid-base forces. This study provides new insights into the adsorption behavior of ENR by MPs.

Phosphoric acid activation of cow dung biochar for adsorbing enrofloxacin in water: Icing on the cake.

In this study, we used different concentrations of H3PO4 to activate pristine biochar (BC) derived from cow dung (BC and BC modified with phosphoric acid at concentrations of 10% (10P-BC), 30% (30P-BC), and 50% (50P-BC)) in order to obtain cheap, high-performance adsorbents. Brunauer-Emmett-Teller analysis, scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, organic element composition determination, and other analyses showed that activation with H3PO4 increased the porosity and hydrophilicity compared with the original BC, thereby enhancing the adsorption properties. The Langmuir isotherm model obtained the best fit and the maximum capacities for adsorbing enrofloxacin by BCs were 12.66 mg/g for BC, 51.90 mg/g for 10P-BC, 63.61 mg/g for 30P-BC, and 26.79 mg/g for 50P-BC. The main mechanisms responsible for antibiotic loading on BC were hydrogen bonding, π-π electron donor-acceptor interactions, pore filling, and electrostatic interactions. Calculations of fixed carbon retention before and after pyrolysis, and adsorption showed that activated BC had a good carbon fixation capacity and it was more capable of adsorbing enrofloxacin compared with the original BC, thereby providing a new method for removing organic pollutants from the environment and reducing carbon emissions. The cost efficiency was analyzed using the improved fuzzy comprehensive evaluation model based on the entropy method. Removal efficiency and utilization efficiency indicators were calculated for the different phosphoric acid activated BCs. The pollutant removal efficiencies were better for 10P-BC and 30P-BC, and the optimal removal efficiency was determined for 30P-BC. Given the current global climate change situation, using 10P-BC and 30P-BC could also help to meet China's carbon neutrality goals by reducing emissions of pollutants containing carbon.

Vitamin C modified crayfish shells biochar efficiently remove tetracycline from water: A good medicine for water restoration.

In this study, crayfish shell biochar (CSB) was modified by introducing vitamin C (VC) with abundant surface functional groups. CSB was impregnated with VC at different ratios and its capacity to adsorb tetracycline (TC) from water was analyzed. The physicochemical properties of CSB were determined by N2 adsorption-desorption isotherm analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. The effects of various factors on adsorption such as the pH, TC concentration, time, and salt ion concentrations were also investigated. Based on the chemical structure of VC, VC can provide CSB with more oxygen-containing functional groups such as hydroxyl groups. The results showed that the CSB modified with VC (CSB-VC) exhibited excellent adsorption of TC, and CSB-VC2 with an impregnation ratio of 2 (gVC/gCSB) had the greatest adsorption performance (saturated adsorption capacity, Qm = 293.36 mg/g), whereas the adsorption performance of CSB alone was about 50% lower (Qm = 172.16 mg/g). The optimal impregnation ratio VC improved the adsorption performance of CSB after modification to 70.4% of the original. Hydrogen bonding, p-p conjugation, pi-pi electron donor-acceptor effect, and π-π interactions were identified as the main adsorption mechanisms. CSB-VC2 was highly effective over a wide range of pH values and at high ion concentrations. Experiments demonstrated the effective regeneration of the adsorbent after multiple cycles, thereby indicating its excellent reusability. It should be noted that the adsorption capacity was good under different water quality conditions, and thus it should exhibit stable adsorption performance under complex water environment conditions.

The carrier effect mechanism of butachlor in water by three typical microplastics.

Butachlor (BUT) is a widely used herbicide that can cause environmental problems when used excessively. BUT has been found to exist in large quantities in the water environment so far. As an agricultural pre-emergent herbicide, BUT can enter the water environment through multiple channels and cause pollution. This study investigated the mechanism of three types of microplastics (MPs): polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) to remove BUT from water. The adsorption behavior between MPs and BUT under different factors, namely pH, salt ion concentration, and aging, was investigated. This study further investigated the desorption and aging of BUT-adsorbed MPs. In this research, the adsorption capacity of BUT by PE, PP, and PVC are 13.65 µg/g, 14.82 µg/g, and 18.88 µg/g, respectively, and the order of carrier effect was: PVC>PP>PE. Experiments show that MPs have low adsorption performance on the microgram level for BUT. The adsorption behavior of PE, PP, and PVC on BUT conformed to pseudo-second-order kinetics, indicating the presence of physical and chemical adsorption. The Langmuir isotherm model fits well, indicating that the adsorption is a single-layer adsorption process. The pH value causes slight fluctuations in the overall carrier effect. Low concentration of salt ions can inhibit the carrier effect, and high concentration will promote the interaction between MPs and BUT. Aging experiments show that the carrier effect of the original materials was higher than the adsorption capacity of hydrogen peroxide and MPs after acid aging, and acid aging can cause the adsorption capacity to drop significantly.

Self-Adaptive Dirhodium Complexes in a Metal-Organic Framework for Synthesis of N-H Aziridines.

Conformational dynamics of active sites in enzymes enable great control over the catalytic process. Herein, we constructed a metal-organic framework with conformationally dynamic active sites (Rh2-ZIF-8). The active sites in Rh2-ZIF-8 were composed of the imidazolate-bridged bimetallic center with a catalytic dirhodium moiety and structural zinc site. Even though the coordination sphere of the dirhodium species was saturated with two circularly arranged esp groups and two axial 2-MeIm ligands, it could still effectively catalyze the direct synthesis of N-H aziridines from olefins with high activity. We found that such a self-adaptive catalytic process was based on the dynamic breakage and reformation of the rhodium-zinc imidazolate bridges. Interestingly, the in situ generated dirhodium site with a unique Rh2(esp)2(2-MeIm)1 configuration was able to exhibit obviously enhanced selectivity compared to homogeneous catalyst Rh2(esp)2. Furthermore, the surrounding zinc imidazolate groups could effectively protect the dirhodium moieties from harsh environments, and this ultimately endowed it with high stability.

[Coronavirus disease 2019 in Northeastern Sichuan: clinical characteristics and treatment analysis of 59 cases].

OBJECTIVE: To analyze the epidemiological, clinical characteristics and treatment of coronavirus disease 2019 (COVID-19) in Northeastern Sichuan, and summarize experience in time to provide reference for clinical diagnosis and treatment. METHODS: A retrospective study was conducted. Fifty-nine patients with COVID-19 admitted to Bazhong Central Hospital and Dazhou Central Hospital from January 27th to February 9th, 2020 were selected as the subjects. The data of demography, epidemiology, laboratory examination, chest CT and related clinical treatment were collected. According to the severity of the disease, the patients were divided into three types: mild, general and severe types, and the differences of the above indices among different clinical types were compared. RESULTS: (1) General information and epidemiology: 31 cases (52.5%) were male, 28 cases (47.5%) were female, the average age was (42.0±16.4) years old, and the patients over 40 years old accounted for the largest proportion (35 cases, 59.3%). The proportion of clinical type was 72.9% (43 cases) in general type, and 62.7% (37 cases) were imported type. With the increase of disease severity, the average age of patients also showed a significant increase trend [the age of the mild, general and severe patients were (30.9±13.6), (42.7±15.3), (55.8±18.9) years old, P < 0.01]. The proportion of patients with more than one basic disease in severe patients was significantly higher than those in mild and general patients [66.7% (4/6) vs. 20.0% (2/10), 9.3% (4/43), both P < 0.05]. In the distribution of clinical symptoms, the proportion of severe patients with chest distress/dyspnea was significantly higher than those in mild and general patients [66.7% (4/6) vs. 10.0% (1/10), 11.6% (5/43), both P < 0.05]. (2) Laboratory examination index: the total number of white blood cell count (WBC), neutrophils count (NEU), C-reactive protein (CRP) in severe patients were higher than those in mild patients and general patients [WBC (×109/L): 7.21±4.35 vs. 5.85±1.69, 5.43±2.04; NEU (×109/L): 6.09±4.43 vs. 3.95±1.45, 3.54±1.83; CRP (mg/L): 16.00 (8.20, 46.43) vs. 5.00 (0.00, 16.13), 15.00 (3.13, 28.58)], the albumin (Alb) level in severe patients was lower than those in mild and general patients (g/L: 38.00±5.35 vs. 49.23±5.27, 39.81±2.15, both P < 0.05), while the hemoglobin (Hb) level in mild patients was higher than that in severe and general patients (g/L: 155.2±12.1 vs. 141.3±6.8, 131.1±11.7, both P < 0.05). (3) Chest imaging: the CT manifestations of typical cases were single or multiple ground glass shadows. With the progress of the disease, the focus gradually increased, the scope gradually expanded, and multiple solid shadows of lung lobes were involved. (4) Treatment: all patients received at least 2 kinds of antiviral therapy, and the application rate of Interferon and Ribavirin in severe patients were higher than those in mild and general patients [100.0% (6/6) vs. 80.0% (8/10), 97.7% (42/43); 83.3% (5/6) vs. 0% (0/10), 20.9% (9/43); all P < 0.05]. (5) Prognosis: until March 6th 2020, 50 patients (84.8%) were discharged from the hospital after rehabilitation, and the remaining 9 patients were still under treatment, none deaths. CONCLUSIONS: The proportion of severe patients with chest distress/dyspnea is higher, the older the patients are and the more basic diseases are, the more likely they are to develop into severe type. High resolution chest CT could be considered for suspected cases or even fever patients, which may show the progress of the disease.

Visible light-enabled selective depolymerization of oxidized lignin by an organic photocatalyst.

The development of an economic, environmental-friendly and energy-saving process for the selective depolymerization of lignin is an outstanding challenge. Herein, a novel and efficient visible-light-induced photocatalytic process for the selective depolymerization of lignin model compounds and organosolv lignin was first developed by using perylene diimide (PDI) as a metal-free organocatalyst. Interestingly, it can completely decompose the oxidized lignin models to phenolic and ketone fragmentation molecules with very high selectivity at room temperature under visible light illumination. Furthermore, the use of a home-made photocatalytic continuous-flow reactor efficiently shortened the reaction time within an hour. Even for organosolv lignin, nearly 86% mass ratio of lignin was degraded to low-molecular-mass monoaromatic or diaromatic products. We found that superior performances were realized by single-electron transfer (SET) from the photoexcited strongly reducing PDI˙- anion to the ketone groups of the ß-O-4 linkage in the lignin.

Primary Amine-Functionalized Mesoporous Phenolic Resin-Supported Palladium Nanoparticles as an Effective and Stable Catalyst for Water-Medium Suzuki-Miyaura Coupling Reactions.

Metal nanoparticles have been recognized and widely explored as unique catalysts for carbon-carbon coupling reactions. However, due to their extreme tendency to agglomeration, the generation and stabilization of metal nanoparticles in a porous matrix is an important research field. Herein, novel mesoporous phenolic resin-supported palladium nanoparticles (Pd@NH2-MPRNs) were prepared via direct anionic exchange followed by gentle reduction by using primary amine-functionalized ordered mesoporous phenolic resin as the support. The obtained Pd@NH2-MPRN material still possessed large surface area and ordered two-dimensional hexagonal mesoporous structure. Meanwhile, uniform and well-dispersed palladium nanoparticles were formed in the mesoporous channels, which could be attributed to an efficient complexation and stabilization effect derived from the primary amine groups. As a result, it can promote Suzuki coupling of less activated aromatic bromides to various biaryls in water with high conversion and selectivity. This excellent performance was attributed to small particle sizes, ordered mesopores, and a hydrophobic pore surface, which resulted in the decreased diffusion limitation and the increased active site accessibility. It is noted that it is competitive with the best palladium catalysts known for water-medium Suzuki coupling reaction, and it can be reused at least seven times without significant reduction in the catalytic efficiency, showing a good recyclability. Therefore, this work provides a new potential platform for designing and fabricating robust ordered mesoporous-polymer-supported metal nanoparticles for various catalytic applications.