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•Optimum proportion of benzoic acid for synthesis of more defects UiO-67.•Defects, methyl and benzene ring enhance π-π interaction to promote VOCs adsorption.•Multiple experiments and ...DFT calculation analyze interaction between VOCs and MOFs.
The harm that is caused by volatile organic compounds (VOCs) has attracted worldwide attention. In production, industrial processes such as fossil fuel combustion, plastics, and paints have caused complex and diverse VOCs emissions. Therefore, studying the phenomenon and influencing factors of typical VOCs adsorption is of practical significance for the treatment of multicomponent VOCs. In this work, defective UiO-67 was prepared by changing the amount of benzoic acid. Then, the adsorption performance was tested, and the adsorption kinetics were considered. The experimental results showed that the 67-ben-10 sample (for which the molar ratio of Zr4+ to benzoic acid was 1:10) achieved the maximum toluene adsorption capacity (480 mg g−1), which was due to the presence of more adsorption sites, higher benzoate content, strong π-π stacking and excellent adsorption diffusion behavior. In addition, the adsorption properties of the 67-ben-10 benzene series (BTX: benzene, toluene, o-xylene, p-xylene and m-xylene) and acetone were further investigated. The results showed that the adsorption performance was related to the polarizability of the VOCs molecules, the method of pore entry and the molecular size. Finally, through desorption experiments, density functional theory (DFT) and kinetics, the binding energy was confirmed to play an important role in adsorption and diffusion.
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In this paper, a simple solvothermal synthesis method was proposed for the preparation of metal organic framework/graphene oxide hybrid nanocomposite (UiO-67/GO). A series of ...UiO-67/GO composites were prepared by varying the addition forms and amounts of GO, and the optimal synthesis conditions were screened. The composites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission Electron Microscope (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), water contact angles (CA) and thermogravimetric analysis (TGA). The adsorption capacity and the adsorption process of toluene were investigated by dynamic adsorption and adsorption kinetics, respectively. The results indicated that 67/GO-0.5% reached the maximum adsorption capacity (876 mg g−1), which far exceeded the other adsorbents. Kinetic model and the Weber-Morris model correlated satisfactorily to the experimental data. The improved adsorption performance was attributed to GO, which enhanced π-π interaction, promoted defect generation and provided more adsorption sites. Finally, the excellent regeneration performance of the adsorbent was verified by temperature programmed desorption (TPD) and cyclic adsorption–desorption experiments. Moreover, the adsorption mechanism was further revealed. Combined with the related adsorption experiments and the density functional theory (DFT) analysis, the efficient removal of toluene by UiO-67/GO was attributed to the cooperation of defects, π-π interaction and hydrogen bonding.
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The severe hazards on ecological environment and human body caused by volatile organic compounds (VOCs) have attracted worldwide substantial attention. In this research, a series of ...novel modified Universitetet i Oslo-67 (UiO-67) with water resistance were prepared and characterized, which had modified by benzoic acid and dopamine hydrochloride (67-ben-DH). On this basis, the adsorption performance, adsorption kinetics, defect engineering and water resistance of adsorbent were investigated. The results indicated that the excellent pore structure and specific surface area of 67-ben-DH-6 (molar ratio of Zr4+ to DH was 1:6) were retained while the adsorption performance and water resistance of the adsorbent were improved. Due to more defects, excellent adsorption diffusion and strong π-π interactions of 67-ben-DH-6, it performed the maximum adsorption capacity of toluene (793 mg g−1). Furthermore, the outstanding water resistance was attributed to the fact that N element of DH reduced the affinity of the adsorbent with water. Finally, the density functional theory (DFT) calculations showed that the adsorbent 67-ben-DH-6 had the maximum adsorption energy for toluene (-99.4 kJ mol−1) and the minimum adsorption energy for water (-17.8 kJ mol−1). Thus, the potential mechanism of 67-ben-DH for efficient toluene adsorption and water resistance was verified from a microscopic perspective.
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•A facile defect-engineering approach was used to synthesis UiO-67.•The high toluene uptake is obtained due to missing and compensating linker defects.•Water molecule exhibited ...promoting effect on the toluene adsorption of UiO-67.•Synergic effects between π-π, OH-CH3 and OH-π obviously enforced toluene adsorption.
A facile defect-engineering approach enabled by introducing monocarboxylic acid modulators (acetic acid, formic acid and benzoic acid) was conducted in this paper. The greatest toluene uptake (480 mg g−1) was obtained on defective UiO-67 synthesized with benzoic acid due to highest missing linker defects and higher compensating linker defects. It is worth mentioning that water molecule exhibited creative promoting effect on the adsorption behavior of defective UiO-67. The original structure of defective UiO-67 was inevitably destroyed under water-containing environment due to the coordination between water molecule and metal cluster. 1H NMR analysis demonstrated that slight loss of BPDC linkers and benzoate linkers due to occupied binding sites, more extra adsorption sites were generated in this process. Furthermore, adsorption mechanisms were studied via density functional theory (DFT) calculations. The synergic effects between π-π, OH-CH3 and OH-π hydrogen bonding strength obviously enforced toluene adsorption, and OH-π exhibited strongest interaction. Moreover, under the circumstance of structural changes due to water molecules, abundant μ3-OH groups were exposed and hydrogen bond interaction was strengthened, which greatly promoted toluene adsorption. Finally, experimental results as well as computational studies forecasted the potentials of defect-tunable MOFs as promising materials in gas adsorption.
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The construction of metal–organic frameworks (MOFs) with highly efficient capture for volatile organic compounds (VOCs) adsorption under humid conditions is a significant yet ...formidable task. Herein, series of fluorinated UiO-67 modified with trifluoroacetic acid (TFA) and 4-fluorobenzoic acid were successfully synthesized for VOCs adsorption under high humidity conditions. Experiments results showed that UiO-67 modified with 4-fluorobenzoic acid (67-F) presented excellent adsorption capacity of 345 mg/g for toluene adsorption and exhibited great water resistance (10.0 vol% H2O, 374 mg/g toluene adsorption capacity). Characterization results indicated that the introduction of 4-fluorobenzoic acid induced the competitive coordination between 4-fluorobenzoic acid and 4,4-biphenyl dicarboxylic acid (BPDC) with Zr4+, causing the formation of abundant defects to provide extra adsorption sites. Meanwhile, the benzene ring in 4-fluorobenzoic acid enhanced the π-π conjugation, causing the further promotion of VOCs adsorption capacity. More importantly, the water resistance mechanism was investigated and elucidated that the introduction of F decreased the surface energy of 67-F and its affinity with water. Meanwhile, the metal complex induced by the fluorinated modification produced an electron-dense pore environment, which greatly improved its chemical and water stability. This work provided a strategy for preparing an adsorbent with high water resistance for real-world VOCs adsorption at high humidity conditions.
Precipitation nowcasting is an important tool for nowcasting weather. In recent years, progress has been achieved in some models based on deep learning for precipitation nowcasting. However, these ...models do not consider the contextual relationships between the input data and the output of a network and their deficiency in capturing the information of prediction objects. To overcome these shortcomings, in this study, we propose a model that performs convolution operation on input data and the output of a Long short-term memory (LSTM) networks. Second, a self-attention operation is added to capture the local and global dependencies of the hidden state of LSTM. The proposed network structure is inserted in an encoding-forecasting network framework and applied to spatiotemporal sequence forecasting. Third, the outputs of the precede sequence are also regarded as the inputs of according LSTM layer and this operation effectively captures temporal feature of sequence data. Comprehensive experiments are conducted on the KTH action dataset and Hong Kong observation 07 radar echo maps dataset. The visual and quantitative prediction results demonstrate the accuracy and efficacy of the proposed model.
The exhumation history of the Central Tibetan Mountain Range (CTMR) in the Qiangtang terrane is important for establishing the boundary conditions prior to the India-Asia collision. Previous studies ...suggest that the CTMR is a significant provenance for Jurassic sediments in the Qiangtang terrane. The Middle Jurassic sediments north of the CTMR provide crucial information to constrain the timing of exhumation in the source area. Here we present detailed stratigraphic sections and detrital zircon U-Pb geochronology in the northern Qiangtang basin. Sedimentary facies analyses indicate that the Early-Middle Jurassic Quemoco Formation is mainly deposited in the deltaic system and carbonate-platform environment. Upsection, the Middle Jurassic Xiali Formation was deposited in a prodelta environment. Combined analyses of palaeocurrent indicators, conglomerate clast composition and U-Pb age spectra suggest that the CTMR is the main provenance for the Quemoco and Xialai formations; while the Triassic southern Qiangtang strata and Jinsha suture are the secondary source areas. The changes in the specific position of detrital zircon U-Pb age peaks around 500 Ma indicate evolving source terranes. Detrital zircon U-Pb geochronological data from the base of the Quemoco Formation and top of the Xiali Formation constrain the conservative maximum depositional ages to be 174.8 ± 1.0 and 161.7 ± 2.3 Ma, respectively. Combined with previous geochronology data, structural geology, and provenance studies across the Qiangtang terrane, the CTMR experienced rapid exhumation during Middle Jurassic and Late Cretaceous and slow exhumation since Eocene. The Jurassic uplift and exhumation of the CTMR were accompanied by the uplift of the southern Qiangtang terrane. The deformation and exhumation history is in favour of the hypothesis that plateau growth in the south-central Qiangtang terrane initiated during the Mesozoic, which is an important initial condition to quantify Cenozoic growth of the Tibetan Plateau.
This study is the first to use the observation data of a fog monitor, a visibility meter, and an automatic weather station to carry out a comprehensive observation experiment from the perspective of ...microphysics on a severe sea fog process in Beilun District, China, from 14 to 15 June 2021. The results show the following: (1) Temperature is closely related to nucleation, condensation growth, and other processes. The decrease (increase) in temperature is the main reason for the enhancement (weakening) of nucleation and the growth of condensation (evaporation of droplets), which leads to an increase (or decrease) in microphysical quantities, such as droplet number concentration and liquid water content. (2) The average droplet number spectral distribution roughly conforms to the Gamma distribution, and the spectral distribution of the fog process presents a ”multi-peak” structure, with peak diameters of 6 μm, 12 μm, 16 μm, 24 μm, and 44 μm. Droplets with a diameter of less than 16 μm account for 75% of the droplet size distribution. (3) During this sea fog process, three microphysical parameters, namely, number concentration, liquid water content, and average diameter, are all positively correlated in pairs, but the positive correlation between the number concentration and the average diameter is weak. This shows that the condensation nucleation and the condensation growth of droplets are the main processes in this sea fog process and that the collision process occurs but is not the dominant process. The sea fog comprehensive observation experiment provides an important demonstration of the microphysics research of sea fog in the eastern coastal areas of China and provides more reference information for sea fog research and equipment comparisons between different regions. At the same time, it also provides an essential scientific basis for the short-term forecast of sea fog in the future and for the optimization of the microphysical parameters of related models.
Tornadoes are highly destructive small-scale extreme weather processes in the troposphere. The weather radar is one of the most effective remote sensing devices for the monitoring and early warning ...of tornadoes. The existing tornado detection algorithms based on radar data are unsupervised and have strict multi-altitude constraints, such as the tornado detection algorithm based on tornado vortex signatures (TDA-TVS), which may lead to high false alarm rates, and the performance of the detection algorithm is greatly affected by the radar data quality control algorithm. A novel TDA-RF algorithm based on the random forest (RF) classification algorithm is proposed for real-time tornado identification of the S-band China new generation of Doppler weather radar (CINRAD-SA). The TDA-RF algorithm uses velocity features to identify tornadoes and adds features related to reflectivity and velocity spectrum width in radar level-II data. Historical CINRAD-SA tornado data from 2006–2015 are used to construct the tornado dataset and train the TDA-RF model. The performance of TDA-RF is evaluated using CINRAD-SA data from five tornadoes of 2016–2020 with enhanced Fujita(EF) scale ratings ranging from EF0 to EF4 and distances from 10 to 130 km to the radar. TDA-RF performs well overall with the probability of detection (POD), false alarm ratio (FAR), and critical success index (CSI) of 71%, 29%, and 55%, respectively. Moreover, the TDA-RF improves POD and CSI, and reduces FAR compared to the TDA-TVS. The maximum tornado early-warning time of TDA-RF is 17 min, and the average is 6 min; TDA-RF can provide classification probability according to the tornado generation and development process to facilitate tracking ability.
As extremely violent meteorological disasters, tornadoes often cause serious casualties. The study aims to analyze the characteristics and causes of tornado injuries in China under certain humanistic ...and geographical conditions.
A random sampling questionnaire survey was developed and distributed to tornado victims from two separate occurrences: an Enhanced Fujita 4 tornado in Yancheng, and a Fujita 3 tornado in Chifeng. The information of demographic characteristics, disaster environment, and individual behaviors in victims was collected. Chi-square test and binary logistic regression were used to analyze influencing factor of injuries.
A total of 94 valid questionnaires (participation rate 95.9%) were finally collected in Yancheng tornado and 67 valid questionnaires (participation rate 93.1%) in Chifeng tornado. Residents' annual income (OR = 0.10, 95% CI 0.02-0.50, P = 0.005), degree of house collapse (OR = 183.12, 95% CI 8.04-4173.34, P = 0.001) have a significant impact on the probability of injury. Differences in tornado disaster drill awareness (P = 0.009), individual behaviors (P = 0.011) and fear level (P = 0.011) significantly affected the incidence of trauma. Whether victims were indoors or not has no statistical difference on injuries in China.
Our study clarifies risk factors and is conducive to the expansion of the investigation in tornado casualties. The government should improve the wind-resistance of residential buildings. Victims should participate in disaster prevention drills to take effective disaster avoidance actions.
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