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The multimetallic sulfur‐framework catalytic site of biological nitrogenases allows the efficient conversion of dinitrogen (N2) to ammonia (NH3) under ambient conditions. Inspired by biological nitrogenases, a bimetallic sulfide material (FeWSx@FeWO4) was synthesized as a highly efficient N2 reduction (NRR) catalyst by sulfur substitution of the surface of FeWO4 nanoparticles. Thus prepared FeWSx@FeWO4 catalysts exhibit a relatively high NH3 production rate of 30.2 ug h−1 mg−1 cat and a Faraday efficiency of 16.4 % at −0.45 V versus a reversible hydrogen electrode in a flow cell; these results have been confirmed via purified 15N2‐isotopic labeling experiments. In situ Raman spectra and hydrazine reduction kinetics analysis revealed that the reduction of undissociated hydrazine intermediates (M‐NH2‐NH2) on the surface of the bimetallic sulfide catalyst is the rate‐determing step for the NRR process. Therefore, this work can provide guidance for elucidating the structure–activity relationship of NRR catalysts., Inspired by biological nitrogenases, a bimetallic sulfide material (FeWSx@FeWO4) was synthesized for a highly efficient N2 reduction (NRR) catalyst. In situ Raman spectra and hydrazine reduction kinetics analysis revealed that the reduction of undissociated hydrazine intermediates (M‐NH2‐NH2) on the surface of the catalyst is the rate‐determing step for the NRR process.

High loadings of nitrate (NO3-) in the aerosol over China significantly exacerbate the air quality and pose a great threat to ecosystem safety through dry–wet deposition. Unfortunately, limited ground-level observation data make it challenging to fully reflect the spatial pattern of NO3- levels across China. Until now, long-term monthly particulate NO3- datasets at a high resolution were still missing, which restricted the assessment of human health and ecosystem safety. Therefore, a unique monthly NO3- dataset at 0.25∘ resolution over China during 2005–2015 was developed by assimilating surface observations, satellite products, meteorological data, land use types and other covariates using an ensemble model combining random forest (RF), gradient-boosting decision tree (GBDT), and extreme gradient-boosting (XGBoost) methods. The new developed product featured an excellent cross-validation R2 value (0.78) and relatively lower root-mean-square error (RMSE: 1.19 µg N m−3) and mean absolute error (MAE: 0.81 µg N m−3). Besides, the dataset also exhibited relatively robust performance at the spatial and temporal scales. Moreover, the dataset displayed good agreement with (R2=0.85, RMSE=0.74 µg N m−3, and MAE=0.55 µg N m−3) some unlearned data collected from previous studies. The spatiotemporal variations in the developed product were also shown. The estimated NO3- concentration showed the highest value in the North China Plain (NCP) (3.55±1.25 µg N m−3); followed by the Yangtze River Delta (YRD) (2.56±1.12 µg N m−3), Pearl River Delta (PRD) (1.68±0.81 µg N m−3), and Sichuan Basin (1.53±0.63 µg N m−3), and the lowest one in the Tibetan Plateau (0.42±0.25 µg N m−3). The higher ambient NO3- concentrations in the NCP, YRD, and PRD were closely linked to the dense anthropogenic emissions. Apart from the intensive human activities, poor terrain condition might be a key factor for the serious NO3- pollution in the Sichuan Basin. The lowest ambient NO3- concentration in the Tibetan Plateau was contributed by the scarce anthropogenic emission and favourable meteorological factors (e.g. high wind speed). In addition, the ambient NO3- concentration showed a marked increasing tendency of 0.10 µgNm-3yr-1 during 2005–2014 (p

Seawater oxygen evolution is one of the promising energy conversion technologies for large-scale renewable energy storage. It requires efficient catalysts to accelerate the oxygen evolution reactio...

The artificial photosynthesis for visible-light-driven CO2 reduction with H2O is promising to solve both energy and environmental issues simultaneously. Herein, we have successfully fabricated all-solid-state Z-scheme ternary photocatalysts, consisting of two isolated photochemical systems of graphitic carbon nitride (g-C3N4) and three-dimensional ordered macroporous carbon-coated TiO2 (3DOM-TiO2@C) combined with Pt nanoparticles as electron-transfer system. Photonic crystal structure and carbon-coated nanolayers of 3DOM-TiO2@C support enhance visible light-harvesting efficiency. The vectorial photoelectron transferring of TiO2@C → Pt → g-C3N4 boosts the separation and surface enrichment efficiencies of photogenerated electrons and holes. All-solid-state Z-scheme ternary photocatalyst exhibits the outstanding yields of CH4 (6.56 μmol h−1, 0.1 g catalyst) and high-efficient quantum efficiency (5.67%) during visible-light-driven conversion of CO2 with H2O. The surface enrichment of electrons and CO2 is the rate-determining step of selective CO2 photoreduction. This study is expected to throw new light on the fabrication of high-efficient photocatalyst for CO2 conversion to hydrocarbon.

We developed a two-stage model called the random-forest–generalised additive model (RF–GAM), based on satellite data, meteorological factors, and other geographical covariates, to predict the surface 8 h O3 concentrations across the remote Tibetan Plateau. The 10-fold cross-validation result suggested that RF–GAM showed excellent performance, with the highest R2 value (0.76) and lowest root-mean-square error (RMSE) (14.41 µ g m −3 ), compared with other seven machine-learning models. The predictive performance of RF–GAM showed significant seasonal discrepancy, with the highest R2 value observed in summer (0.74), followed by winter (0.69) and autumn (0.67), and the lowest one in spring (0.64). Additionally, the unlearning ground-observed O3 data collected from open-access websites were applied to test the transferring ability of the novel model and confirmed that the model was robust in predicting the surface 8 h O3 concentration during other periods ( R2=0.67 , RMSE = 25.68 µ g m −3 ). RF–GAM was then used to predict the daily 8 h O3 level over the Tibetan Plateau during 2005–2018 for the first time. It was found that the estimated O3 concentration displayed a slow increase, from 64.74±8.30 µ g m −3 to 66.45±8.67 µ g m −3 from 2005 to 2015, whereas it decreased from the peak to 65.87±8.52 µ g m −3 during 2015–2018. Besides this, the estimated 8 h O3 concentrations exhibited notable spatial variation, with the highest values in some cities of the northern Tibetan Plateau, such as Huangnan ( 73.48±4.53 µ g m −3 ) and Hainan ( 72.24±5.34 µ g m −3 ), followed by the cities in the central region, including Lhasa ( 65.99±7.24 µ g m −3 ) and Shigatse ( 65.15±6.14 µ g m −3 ), and the lowest O3 concentration occurred in a city of the southeastern Tibetan Plateau called Aba ( 55.17±12.77 µ g m −3 ). Based on the 8 h O3 critical value (100 µ g m −3 ) provided by the World Health Organization (WHO), we further estimated the annual mean nonattainment days over the Tibetan Plateau. It should be noted that most of the cities on the Tibetan Plateau had excellent air quality, while several cities (e.g. Huangnan, Haidong, and Guoluo) still suffered from more than 40 nonattainment days each year, which should be given more attention in order to alleviate local O3 pollution. The results shown herein confirm that the novel hybrid model improves the prediction accuracy and can be applied to assess the potential health risk, particularly in remote regions with few monitoring sites.

The adverse health effects of volatile organic compounds (VOCs) highlight the need of spatiotemporal models to assess exposure for epidemiological studies. Herein, a geographically and temporally weighted regression (GTWR) model was developed to estimate the spatial variability of the VOCs, including acetone, benzene, toluene, and m/p-xylene in Yangpu (YP) District, Shanghai, China. The GTWR model shows a good prediction performance, with cross-validation (CV) R2 = 0.60, 0.75, 0.64, and 0.62 for acetone, benzene, toluene, m/p-xylene, respectively. Moreover, the GTWR model outperforms the ordinary least squares (OLS), geographically weighted regression (GWR), and temporally weighted regression (TWR) model in terms of higher CV R2 and lower CV root mean square error (RMSE) values. The 100 m × 100 m gridded concentrations of acetone, benzene, toluene and m/p-xylene estimated from the GTWR model range from 1.57 to 2.57 ppbv, 0.24–1.06 ppbv, 0.40–1.56 ppbv, and 0.31–1.05 ppbv, respectively. Among them, the concentrations of acetone, toluene and m/p-xylene are far below the thresholds of the United States Environmental Protection Agency (USEPA), whereas the benzene concentrations are higher than that of the USEPA's standard by 2–10 times. The VOC emissions are closely associated with transportation, industrial activities, commercial activities, and the release from recreational areas. The lifetime cancer risk (LCR) of benzene for juveniles, adults and elderly are in the range of 2.3 × 10−5- 0.98 × 10−5, 3.1 × 10−5-1.4 × 10−4, and 3.7 × 10−5-1.6 × 10−4, respectively, indicating potential and high cancer risks to human health. The integrated non-cancer risks (HQ) of four VOC species are far below the safe level (=1), suggesting a negligible non-cancer risk for residents living in YP District.

Background: High plasma levels of trimethylamine N-oxide (TMAO) and its precursor choline have been linked to stroke; however, their association with cerebral small vessel disease remains unclear. Here we evaluated the association of plasma levels of TMAO and choline with imaging markers of cerebral small vessel disease, including white matter hyperintensities, lacunes, and cerebral microbleeds.Methods: We performed a baseline cross-sectional analysis of a multicenter hospital-based cohort study from 2015 to 2018. The data were collected from 30 hospitals in China and included 1,098 patients with ischemic stroke/transient ischemic attack aged ≥18 years. White matter hyperintensities, lacunes, and cerebral microbleeds were evaluated with the patients' demographic, clinical, and laboratory information removed. White matter hyperintensities were rated using the Fazekas visual grading scale, while the degree of severity of the lacunes and cerebral microbleeds was defined by the number of lesions.Results: Increased TMAO levels were associated with severe white matter hyperintensities [adjusted odds ratio (aOR) for the highest vs. lowest quartile, 1.5; 95% confidence interval (CI), 1.0–2.1, p = 0.04]. High TMAO levels were more strongly associated with severe periventricular white matter hyperintensities (aOR for the highest vs. lowest quartile, 1.6; 95% CI, 1.1–2.3, p = 0.009) than deep white matter hyperintensities (aOR for the highest vs. lowest quartile, 1.3; 95% CI, 0.9–1.9, p = 0.16). No significant association was observed between TMAO and lacunes or cerebral microbleeds. Choline showed trends similar to that of TMAO in the association with cerebral small vessel disease.Conclusions: In patients with ischemic stroke or transient ischemic attack, TMAO and choline appear to be associated with white matter hyperintensities, but not with lacunes or cerebral microbleeds; TMAO and choline were associated with increased risk of a greater periventricular, rather than deep, white matter hyperintensities burden.

A new and efficient method for the synthesis of 2-trifluoromethyl-2-hydroxy-2H-chromenes was developed via intermolecular cyclization of (Z)-trifluoromethyl alkenyl triflates and salicylaldehydes. A series of 2-trifluoromethyl-2-hydroxy-2H-chromenes with aryl or alkyl groups at 3-position have been obtained in moderate to excellent yields. And a key intermediate, 3-phenyl-4-(pyrrolidin-1-yl)-2-(trifluoromethyl)chroman-2-ol (6), was isolated and fully characterized, which suggests that the elimination of pyrrolidine from this intermediate is the last step during the formation of 2-trifluoromethyl-2-hydroxy-2H-chromenes.

Artificial photosynthesis efficiency for selective CO2 conversion to CH4 as chemical energy-rich molecule is dependent on the photogenerated charges separation and reactant adsorption property of photocatalyst. Here we report a novel fabrication of core-shell-structured photocatalysts of Pt/TiO2-nanocrystals wrapped by reduced graphene oxide (rGO) sheets ((Pt/TiO2)@rGO). The ultrafine anatase TiO2 nanocrystals with coexposed {001} and {101} facets acted as the fountain of the photogenerated charges primitively. Pt nanoparticles (NPs) deposited on the TiO2 nanocrystals can gather and transfer the stimulated electrons originated from anatase TiO2 nanocrystals. The all-solid-state electron multiple transmission (EMT) system with TiO2-nanocrystal(core)-Pt(mediator)-rGO(shell) nanojunction is not only favorable to the vectorial electron transfer of TiO2 → Pt → rGO and enhance the separation efficiency of photogenerated electrons and holes, but also the surface residual hydroxyl and extended π bond of wrapping rGO sheets can improve the adsorption and activation capabilities for CO2 reactant. (Pt/TiO2)@rGO ternary photocatalysts exhibit excellent performance for the multi-electron process of selective photocatalytic CO2 conversion to CH4. Among the prepared catalysts, (Pt/TiO2)@rGO-2 catalyst shows the highest photocatalytic activity and selectivity for CO2 conversion, i.e., the formation rate of CH4 is 41.3 μmol g−1 h−1 and the selectivity of CO2 conversion to CH4 product is 99.1%, and its apparent quantum efficiency for CH4 product is 1.93%. As a heuristic the fabrication of core-shell structured (Pt/TiO2)@rGO photocatalysts will stimulate more novel ideas for application to light-chemical energy conversion.

A base-controlled regiodivergent azidation of trifluoromethyl alkenyl triflates providing either (E)-3-azido-1-aryl-4,4,4-trifluorobut-1-ene (CF3-containing allyl azides) or (Z)-1-azido-1-aryl-4,4,4-trifluorobut-1-ene (CF3-containing alkenyl azides) is described. Catalyzed by Et3N, the azidation of trifluoromethyl alkenyl triflates with TMSN3 gave CF3-containing allyl azides. On the other hand, using stoichiometric DBU, the regioisomeric azidation products, CF3-containing alkenyl azides, were obtained in good yield. A further transformation for CF3-containing amines, triazoles, and azirines highlights the practical applicability of this transition-metal-free protocol.

The photocatalytic conversion of CO2 and H2O into value-added chemicals using sunlight is significant to solve energy crisis and environmental problems. In this work, a series of novel bifunctional catalysts of core-shell structured AuPd nanoparticles decorated 3DOM TiO2 (AuPd/3DOM-TiO2) w were successfully fabricated via a facile one-pot method of gas bubbling-assisted membrane reduction (GBMR). AuPd/3DOM-TiO2 catalysts show uniform 3D ordered macroporous structure, and the slow photon effect of 3DOM-TiO2 as a photonic crystal can enhance light-harvesting efficiency. AuPd nanoparticles are highly dispersed on the surface of 3DOM-TiO2 carrier. Since bimetallic AuPd nanoparticles with the relatively low Fermi level have good capacity of trapping electron, they can efficiently promote the separation of photogenerated electron-hole pairs in TiO2. The AuPd/3DOM-TiO2 catalysts exhibit excellent photocatalytic activity for CO2 reduction with H2O to CH4 under light irradiation. Among the studied catalysts, Au3Pd1/3DOM-TiO2 catalyst exhibits the highest photocatalytic activity and selectivity for CO2 reduction, e.g., its formation rate of CH4 is 18.5 μmol g−1 h−1 and its selectivity to CH4 production by CO2 reduction is 93.9%. The possible mechanism of AuPd/3DOM-TiO2 catalysts for photocatalytic CO2 reduction is also proposed, and it would guide further design and synthesis of high efficient photocatalysts for CO2 reduction with H2O.

Nitrous acid (HONO) plays a significant role in tropospheric chemistry. The emission sources of HONO, however, are poorly characterized, which constraints the predictive capabilities of HONO and the associated environmental influences in models. This study measured the emission factors of HONO (EFHONO) from the agricultural residue (including wheat, rice, corn and soybean straws) open burning, the largest biomass combustion source in China. Based on this, a high-resolution (0.25 ° × 0.25 °) emission inventory of HONO from 2011 to 2015 was established using the city-level activity data compiled through statistical yearbook review in combination with machine learning algorithms, including linear regression (LR), back-propagation neural network (BPNN), general regression neural network (GRNN) and random forest (RF). Results showed that the averaged EFHONO from open burning of wheat, rice, corn and soybean straws were 0.10, 0.25, 0.98 and 0.97 g kg−1, respectively. Total annual emissions of HONO were estimated to be 101347.3, 100232.1, 104278.3, 98383.0 and 107783.9 tons, respectively, for 2011–2015. Regions with high HONO emission intensities were mainly concentrated in North China Plain and Northeast China, whereas low intensities were mainly allocated to western regions. The temporal distribution of average provincial emissions showed the peaks in March, April, June and October, respectively. Results shown herein should be useful for improving the accuracy of HONO budgets and air quality simulations in China.

An efficient method for the synthesis of (Z)-selective α-trifluoromethyl alkenyl triflates is described. As an important fluorinated building block, it is utilized successfully for the synthesis of various trifluoromethyl derivatives such as diarylethylenes, enynes, alkynes, and benzofurans.

Size-segregated aerosol samples were collected in the land-sea boundary zone of East China, the offshore area of East China Sea (ECS), to determine the concentrations of water-soluble inorganic nitrogen (WSIN), water-soluble organic nitrogen (WSON), urea, and free amino acids (FAAs), to quantify their sources, and to estimate their dry deposition fluxes. The results indicated that the mean concentrations of WSIN, WSON, urea, and FAAs in total suspended particle (TSP) were 547.14 nmol/m3, 258.64 nmol/m3, 12.69 nmol/m3, and 2589.03 pmol/m3, respectively. The WSIN, WSON, and urea concentrations in TSP showed remarkably spatial variation with the higher one during the shipping line (SL) 1 and SL4, while they exhibited the lower ones during SL3 and SL5. The biomass burning and fertilizer application in the continent provided important precursors for WSIN, WSON, and urea in the offshore areas. Besides, O3-related photochemical process also promoted the secondary formation of these species. In contrast, these anthropogenic sources played the minor roles on the relatively remote marine region (SL5). It was interesting to note that the total FAAs during SL5 did not show the lowest concentration, which might be contributed by the bubble bursting on the sea surface and the release of bacteria. The Positive Matrix Factorization (PMF) method identified fertilizer application and secondary formation were important sources for WSIN (35.54% and 27.53%) and WSON (43.07% and 40.46%), respectively. However, fertilizer application and combustion sources played the crucial important roles on urea (65.93% and 19.13%) and FAAs (51.35% and 16.35%). The mean dry deposition fluxes of WSIN, WSON, urea, and FAAs in the ECS offshore area were 206763.57 nmol m−2 d−1, 103763.07 nmol m−2 d−1, 4746.20 nmol m−2 d−1, and 1047.08 nmol m−2 d−1, respectively. The present study revealed that the ambient N-bearing particles in the land-sea boundary zone suffered from the combined effects of continental transport and the release of marine organisms.

A method for the synthesis of allylboronates by iron-catalyzed boration of allylic alcohols with H3BO3 as an additive is developed. The introduction of H3BO3 promotes the cleavage of C‒O bond in allylic alcohols obviously. Functional groups, such as fluoro, chloro, bromo, alkyl, and alkoxy, are tolerated well. Thus, various allylboronates are obtained in acceptable yield.

A Pd-catalyzed hydrogenation of (Z)-trifluoromethyl alkenyl triflate providing either (Z)- or (E)-3,3,3-trifluoropropenyl derivatives with excellent divergent geometric control in good yield is described. Catalyzed by Pd(OAc)2/PPh3, the reduction of (Z)-trifluoromethyl alkenyl triflates with HSiEt3 gave (E)-3,3,3-trifluoropropenyl derivatives, and while using HCOOH/Et3N as the reducing agent, the (Z)-isomers were obtained through an elimination/hydrogenation tandem pathway. Both transformations showed excellent geometrical selectivity.

A highly selective and atom efficient ‘trifluoroacetic ester/ketone metathesis’ has been sincerely witnessed. Enolizable alkyl (at least two non-hydrogen atoms) aryl ketones were found to react readily with ethyl trifluoroacetate under the promotion of NaH to afford trifluoroacetic ester/ketone exchange products, trifluoromethyl ketones (TFMKs), and aromatic acid esters, which were quite different from the general Claisen condensation products, 1,3-diketones. The outcome of the reaction between ketone and ethyl trifluoroacetate is strongly related to the structures of substrates, the steric congestion caused by alkyl group is in favor of the C–C bond cleavage. DFT investigation further disclosed that the metathesis reaction was a kinetically favored pathway. Using only a slight excess of cheap trifluoromethylation reagent, simple operation and mild conditions make it a practical method for preparation of TFMKs on large scale, as well as a new choice of converting aryl alkyl ketones to aromatic acid esters.

Reversible photoswitched triplet-triplet annihilation upconversion (TTA UC) was demonstrated with dithienylethene (DTE) derivatives as the photochromic units, 2,6-diiodoBodipy as the triplet photosensitizer, and perylene as the triplet acceptor/emitter. The TTA UC is undisturbed by the open-form DTE but can be switched OFF upon photoirradiation of the mixture of the three components at 254 nm, i.e., by the closed-form DTE. Subsequent visible light irradiation restores the TTA UC. By studying the competitive triplet-state energy-transfer processes with nanosecond time-resolved transient difference absorption and fluorescence spectroscopy, we confirmed that the quenching of the perylene triplet excited state by closed-form DTE is dominant among the four possible quenching processes.

An efficient method for the synthesis of (Z)-selective α-trifluoromethyl alkenyl triflates is described. As an important fluorinated building block, it is utilized successfully for the synthesis of various trifluoromethyl derivatives such as diarylethylenes, enynes, alkynes, and benzofurans.

Enolizable alkyl aryl ketones react with ester (II) to produce the 2 types of title compounds.