Multiple-Emitting Luminescent Metal-Organic Framework as an Array-on-a-MOF for Rapid Screening and Discrimination of Nitroaromatics.

Fluorescence array technologies have attracted great interest in the sensing field because of their high sensitivity, low cost, and capability of multitarget detection. However, traditional array sensing relies on multiple independent sensors and thus often requires time-consuming and laborious measurement processes. Herein, we introduce a novel fluorescence array strategy of the array-on-a-metal-organic framework (MOF), which integrates multiple array elements into a single MOF matrix to achieve facile sensing and discrimination of multiple target analytes. As a proof-of-concept system, we constructed a luminescent MOF containing three different emitting channels, including a lanthanide ion (europium/Eu3+, red emission), a fluorescent dye (7-hydroxycoumarin-4-acetic acid/HCAA, blue emission), and the MOF itself (UiO-66-type MOF, blue-violet emission). Five structurally similar nitroaromatic compounds (NACs) were chosen as the targets. All three channels of the array-on-a-MOF displayed rapid and stable fluorescence quenching responses to NACs (response equilibrium achieved within 30 s). Different responses were generated for each channel against each NAC due to the various quenching mechanisms, including photoinduced electron transfer, energy competition, and the inner filter effect. Using linear discriminant analysis, the array-on-a-MOF successfully distinguished the five NACs and their mixtures at varying concentrations and demonstrated good sensitivity to quantify individual NACs (detect limit below the advisory concentration in drinking water). Moreover, the array also showed feasibility in the sensing and discrimination of multiple NACs in real water samples. The proposed "array-on-a-MOF" strategy simplifies multitarget discrimination procedures and holds great promise for various sensing applications.

Robust Activity and Stability of P-Doped Fe-Carbon Composites Derived from MOF for Bromate Reduction.

Iron-based materials are effective for the reductive removal of the disinfection byproduct bromate in water, while the construction of highly stable and active Fe-based materials with wide pH adaptability remains greatly challenging. In this study, highly dispersed iron phosphide-decorated porous carbon (Fe2P(x)@P(z)NC-y) was prepared via the thermal hydrolysis of Fe@ZIF-8, followed by phosphorus doping (P-doping) and pyrolysis. The reduction performances of Fe2P(x)@P(z)NC-y for bromate reduction were evaluated. Characterization results showed that the Fe, P, and N elements were homogeneously distributed in the carbonaceous matrix. P-doping regulated the coordination environment of Fe atoms and enhanced the conductivity, porosity, and wettability of the carbonaceous matrix. As a result, Fe2P(x)@P(1.0)NC-950 exhibited enhanced reactivity and stability with an intrinsic reduction kinetic constant (kint) 1.53-1.85 times higher than Fe(x)@NC-950 without P-doping. Furthermore, Fe2P(0.125)@P(1.0)NC-950 displayed superior reduction efficiency and prominent stability with very low Fe leaching (4.53-22.98 µg L-1) in a wide pH range of 4.0-10.0. The used Fe2P(0.125)@P(1.0)NC-950 could be regenerated by phosphating, and the regenerated Fe2P(0.125)@P(1.0)NC-950 maintained 85% of its primary reduction activity after five reuse cycles. The study clearly demonstrates that Fe2P-decorated porous carbon can be applied as a robust and stable Fe-based material in aqueous bromate reduction.

Efficient Catalytic Oxidation of Ethylene at 0 °C on an in Situ Carbon Modified Pt Catalyst Supported on SBA-15.

The design of efficient catalysts for catalytic ethylene (C2H4) oxidation is of crucial importance for extending the shelf life of fruits and vegetables. Herein, a carbon modified SBA-15 supported Pt catalyst (Pt/CSBA-15) was prepared in situ by a facile solid phase grinding-infiltration-inert atmosphere calcination method. Characterization results reveal that in the Pt/CSBA-15 catalysts thin carbon layers are successfully formed in the hexagonal pores of SBA-15. Additionally, Pt particles are well dispersed in the channels of SBA-15, and Pt/CSBA-15 has a smaller Pt particle size than the catalyst without carbon modification (i.e., Pt/SBA-15). O2 is more feasibly adsorbed and activated on small-sized Pt particles, and in situ formed carbon species enhance the hydrophobicity of catalysts. As a result, both 3Pt/CSBA-15 and 5Pt/CSBA-15 are able to maintain 100% conversion of 50 ppm of C2H4 for more than 7 h at 0 °C. 3Pt/CSBA-15 even achieves 81.5% C2H4 conversion and 71.6% CO2 yield after 20 h, exhibiting much more prominent catalytic performances than 3Pt/SBA-15. DFT calculations and in situ FTIR measurements confirm that small-sized Pt particles possess strong O2 affinity to promote O2 adsorption, and in situ formed hydrophobic carbon layers efficiently suppress competitive H2O adsorption. Such a unique one-step catalyst preparation method for regulating the size of metal particles and the hydrophobicity of catalysts can be perfectly utilized to develop simple and efficient hydrophobic catalysts applied in low-temperature oxidation of C2H4.

Rapid responses of human pluripotent stem cells to cyclic mechanical strains applied to integrin by acoustic tweezing cytometry.

Acoustic tweezing cytometry (ATC) is an ultrasound-based biophysical technique that has shown the capability to promote differentiation of human pluripotent stem cells (hPSCs). This study systematically examined how hPSCs respond to cyclic mechanical strains applied by ATC via displacement of integrin-bound microbubbles (averaged diameter of 4.3 µm) using ultrasound pulses (acoustic pressure 0.034 MPa, center frequency 1.24 MHz and pulse repetition frequency 1 Hz). Our data show downregulation of pluripotency marker Octamer-binding transcription factor 4 (OCT4) by at least 10% and increased nuclear localization of Yes-associated protein (YAP) by almost 100% in hPSCs immediately after ATC application for as short as 1 min and 5 min respectively. Analysis of the movements of integrin-anchored microbubbles under ATC stimulations reveals different stages of viscoelastic characteristic behavior and increasing deformation of the integrin-cytoskeleton (CSK) linkage. The peak displacement of integrin-bound microbubbles increased from 1.45 ± 0.16 to 4.74 ± 0.67 µm as the duty cycle of ultrasound pulses increased from 5% to 50% or the duration of each ultrasound pulse increased from 0.05 to 0.5 s. Real-time tracking of integrin-bound microbubbles during ATC application detects high correlation of microbubble displacements with OCT4 downregulation in hPSCs. Together, our data showing fast downregulation of OCT4 in hPSCs in respond to ATC stimulations highlight the unique mechanosensitivity of hPSCs to integrin-targeted cyclic force/strain dependent on the pulse duration or duty cycle of ultrasound pulses, providing insights into the mechanism of ATC-induced accelerated differentiation of hPSCs.

Ni12P5 Confined in Mesoporous SiO2 with Near-Unity CO Selectivity and Enhanced Catalytic Activity for CO2 Hydrogenation.

CO2 hydrogenation via the reverse water gas shift (RWGS) reaction is a promising strategy for CO2 utilization while constructing Ni-based catalysts with high catalytic activity and perfect CO selectivity remains a great challenging. Here, we demonstrate that the product selectivity for CO2 hydrogenation can be significantly tuned from CH4 to CO by phosphating of SiO2-supported Ni catalysts due to the geometric effect. Interestingly, nickel phosphide catalysts with different crystalline phases (Ni12P5 and Ni2P) differ sharply in CO2 conversion, and Ni12P5 is remarkably more active. Furthermore, we developed a facile strategy to confine small Ni12P5 nanoparticles in mesoporous SiO2 channels (Ni12P5@SBA-15). Enhanced activity is exhibited on Ni12P5@SBA-15, ascribed to the highly effective confinement effect. The in situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculations unveil that catalytic CO2 hydrogenation follows a direct CO2 dissociation route with adsorbed CO as the key intermediate. Notably, strong multibonded CO (threefold and bridge-bonded CO) is feasibly formed on the Ni catalyst accounting for CH4 as the dominant product whereas only weak linearly bonded CO exists on nickel phosphide catalysts resulting in almost 100% CO selectivity. The present results indicate that Ni12P5@SBA-15 combining the geometric effect and the confinement effect can achieve near-unity CO selectivity and enhanced activity for CO2 hydrogenation.

Natural resources for policy makers: Revisiting COVID-19 perspective of aggregate South Asian economies.

The global pandemic of covid-19 affected human lives and the global environment. Further, literature on the nexus of natural resources and economic growth, initiating the pandemic in the 21st century has confronted policymakers with uncertainty. This requires revisiting the link between natural resources and the economic performance of the South Asian economies. For this purpose, the present study has tried to investigate the role of natural resources in the economic growth of the aggregate South Asian economies during the Covid-19 challenge. The analysis has been completed by a novel approach of MMQR taking data from 1980 to 2021. The oil rents have negatively affected the economic growth may be due to its lower demand during the pandemic caused by lockdown activity. The trade and electricity produced from renewable improve the economic performance of the designated sample economies. The results provide evidence of the irreversible investment theory. The analysis implies that efficient policies for natural resources, specifically oil prices, are required to encourage the South Asian economies' role. Further, the positivity of electricity production from renewable gives rise to the growth hypothesis, which depicts that using renewable energy enhances the economic growth of South Asian economies.

A Mass Spectrometry-Machine Learning Approach for Detecting Volatile Organic Compound Emissions for Early Fire Detection.

Mass spectrometry in parallel with real-time machine learning techniques were paired in a novel application to detect and identify chemically specific, early indicators of fires and near-fire events involving a set of selected materials: Mylar, Teflon, and poly(methyl methacrylate) (PMMA). The volatile organic compounds emitted during the thermal decomposition of each of the three materials were characterized using a quadrupole mass spectrometer which scanned the 1-200 m/z range. CO2, CH3CHO, and C6H6 were the main volatiles detected during Mylar thermal decomposition, while Teflon's thermal decomposition yielded CO2 and a set of fluorocarbon compounds including CF4, C2F4, C2F6, C3F6, CF2O, and CF3O. PMMA produced CO2 and methyl methacrylate (MMA, C5H8O2). The mass spectral peak patterns observed during the thermal decomposition of each material were unique to that material and were therefore useful as chemical signatures. It was also observed that the chemical signatures remained consistent and detectable when multiple materials were heated together. Mass spectra data sets containing the chemical signatures for each material and mixtures were collected and analyzed using a random forest panel machine learning classification. The classification was tested and demonstrated 100% accuracy for single material spectra and an average of 92.3% accuracy for mixed material spectra. This investigation presents a novel technique for the real-time, chemically specific detection of fire related VOCs through mass spectrometry which shows promise as a more rapid and accurate method for detecting fires or near-fire events.

A nanozyme-like colorimetric sensing strategy based on persulfate activation on Co-based metal-organic frameworks.

A nanozyme-like colorimetric sensing strategy based on persulfate activation on Co-based metal-organic frameworks is developed for biomolecule detection in solution and on paper strips. By switching from H2O2 activation on nanozymes to catalytic persulfate activation, this general strategy provides higher sensitivity, faster speed, and wider application ranges for detection.

Insight into phase structure-dependent soot oxidation activity of K/MnO2 catalyst.

In the present study, two nanosized MnO2 with ß and δ phase structures and potassium loaded MnO2 catalysts with varied K loading amounts (denoted as K/MnO2) were prepared. Temperature programmed oxidation and isothermal reactions in loose contact modes were employed to examine the soot oxidation activity of the as-prepared catalysts. Characterization results show that as compared with ß-MnO2, δ-MnO2 has larger surface area and higher content of hydroxyl groups. Upon K loading, abundant hydroxyl groups in δ-MnO2 effectively sequestrate K cation to form bound K species and free K species are available only at K loading above 3.0 wt.%. In contrast, the majority of K species present as free state in ß-MnO2 even at a K loading of 1.0 wt.% due to its very low hydroxyl group content. The O2 temperature-programmed desorption (O2-TPD) demonstrates that the catalysts with free K species exhibit strong ability in activating gaseous O2, whereas the catalysts only having bound K display minor O2 activation capability. As a result, despite of slightly lower activity of ß-MnO2 than δ-MnO2, the K/ß-MnO2 catalysts exhibit substantially higher activities than K/δ-MnO2 catalysts with identical K loadings. The finding in this study clearly demonstrates that for MnO2 based catalysts, the enhancement of catalytic activity for soot oxidation is highly K loading amount dependent and the dependency is strongly associated with the phase structure of MnO2.

Polyaniline coated Pt/CNT as highly stable and active catalyst for catalytic hydrogenation reduction of Cr(VI).

Liquid phase catalytic hydrogenation reduction is a feasible method to eliminate Cr(VI) in water, while supported noble metal catalysts are liable to deactivation. In this study, carbon nanotube supported Pt catalyst (Pt/CNT) coated by polyaniline (Pt/CNT@PANI) was prepared and applied in the liquid phase catalytic hydrogenation of Cr(VI). Characterization results disclose that after coating Pt/CNT is completely wrapped by PANI layers and active Pt particles are no longer accessible. Despite complete embedment of Pt particles by PANI layers, Pt/CNT@PANI remains highly active for Cr(VI) reduction in liquid phase catalytic hydrogenation. The catalytic Cr(VI) reduction on Pt/CNT@PANI can be described by a PANI oxidation-reduction mechanism, by which PANI is first oxidized by Cr(VI) to form Cr(III), and oxidized PANI is reduced by catalytic hydrogenation. The Cr(VI) reduction on Pt/CNT@PANI complies with the Langmuir-Hinshelwood model, reflecting the pivotal role of Cr(VI) adsorption. Furthermore, the catalytic activity of Pt/CNT@PANI differs with PANI layer thickness and Cr(VI) reduction is positively correlated with reaction temperature. Catalyst recycling results show that after 4 cycles Pt/CNT loses 92.4% of catalytic activity, while the initial activity of Pt/CNT@PANI slightly decreases by 11.6%, demonstrating its high catalyst stability.

Exosomes derived from M2 Macrophages Improve Angiogenesis and Functional Recovery after Spinal Cord Injury through HIF-1α/VEGF Axis.

Exosomes are nano-sized vesicles that contain a variety of mRNAs, miRNAs, and proteins. They are capable of being released by a variety of cells and are essential for cell-cell communication. The exosomes produced by cells have shown protective benefits against spinal cord damage (SCI). Recently, it was discovered that M2 macrophages aid in the angiogenesis of numerous illnesses. However, the functional role of M2 macrophage-derived exosomes on SCI is unclear. Here, we investigate the pro-angiogenesis of M2 macrophage-derived exosomes on SCI. We founded that M2 macrophage exosomes alleviated tissue damage and enhanced functional recovery post-SCI. We discovered that M2 macrophage exosome administration increased angiogenesis after SCI in vivo using immunohistochemistry, immunofluorescence labeling, and Western blot analysis. Additionally, the expression of the pro-angiogenesis factors, HIF-1α and VEGF, were enhanced with the treatment of the M2 macrophage exosomes. Furthermore, we found that M2 macrophage exosomes enhanced neurogenesis after SCI in vivo. In vitro, we found that M2 macrophage exosomes can be taken up by the brain endothelial cell line (bEnd.3) and that they enhanced the tube formation, migration, and proliferation of bEnd.3 cells. Furthermore, by using special siRNA to inhibit HIF-1α expression, we observed that the expression of VEGF decreased, and the tube formation, migration, and proliferation of bEnd.3 cells were attenuated with the treatment of HIF-1α-siRNA. In conclusion, our findings reveal that M2 macrophage exosomes improve neurological functional recovery and angiogenesis post-SCI, and this process is partially associated with the activation of the HIF-1/VEGF signaling pathway.

Efficient and reductive removal of bromate using a novel and stable nanoscale zero-valent iron embedded in N-doped carbon derived from metal-organic frameworks.

Nanoscale zero-valent iron (nZVI) has drawn great interest in the remediation of contaminated waters. In this study, we prepared a novel and stable nZVI embedded in N-doped carbon matrix (nZVI@MOF-CN) using a facile direct carbonization method, in which an iron-containing metal-organic framework (MOF) served as both the iron and carbon sources, and melamine as the nitrogen source. The nZVI@MOF-CN composites were used in the removal of bromate in water, which could be effectively reduced by the surface electrons transferred from nZVI to the carbon encapsulation layer due to the Schottky-Mott effect. Doped nitrogen significantly facilitated the reduction of bromate by nZVI, because it enhanced the nZVI dispersion and bromate adsorption, and modulated the carbon matrix conductivity. The bromate reduction activity of nZVI@MOF-CN was more than 50 times higher that of its un-doped counterpart and a commercial nZVI. Moreover, owing to the protection of carbon encapsulation layer, nZVI@MOF-CN exhibited good stability and reusability. The leached concentration of iron ions of nZVI@MOF-CN was less than 5% of the commercial nZVI under the same reaction conditions. Commercial nZVI almost completely lost its bromate reduction activity after use (3% reduction efficiency in the examined time frame), while nZVI@MOF-CN maintained a reduction efficiency of 61%. The nZVI@MOF-CN could be effectively regenerated by hydrogenation reduction. After five reaction-regeneration cycles, nZVI@MOF-CN still achieved a bromate reduction efficiency of approximately 80%. These results suggest that MOF-derived nZVI materials are highly reactive and stable for the reductive removal of pollutants in water.

Efficient inhibition of cyanobacteria M. aeruginosa growth using commercial food-grade fumaric acid.

The control of cyanobacteria blooms is a global challenge. Here, we reported the efficient inhibition of M. aeruginosa by fumaric acid (FA), an intermediate metabolite of the tricarboxylic acid cycle. FA showed strong algicidal activity with an inhibition rate of 90.5% on the 8th day at a dose of 40 mg/L. The presence of FA caused severe membrane damage, as suggested by the fluorescence flow cytometry and morphology analysis. FA inhibited the formation of chlorophyll a, interrupting the photosynthesis system. It also induced oxidative stress in cells. Principal component analysis of the indicators suggested that the FA-treated sample had a significantly different inhibitory pattern than the acid-treated sample. Thus, the inhibitory effect was not solely caused by the pH effect. Untargeted metabolomic analysis revealed that 31 metabolites were differentially expressed in response to FA stress, which were mainly involved in the metabolite processes and the membranes. A commercial food-grade FA was able to inhibit the growth of M. aeruginosa similar to the analytical-grade FA. Our results suggest that FA can be potentially an efficient and low-risk chemical for inhibiting M. aeruginosa growth, which may find future applications in cyanobacteria bloom control.

Data-driven analysis and new findings on the loss of tail rotor effectiveness in helicopter accidents.

Loss of tail rotor effectiveness (LTE) is an unstable dynamic phenomenon that affects single-rotor helicopters and frequently leads to accidents. LTE accidents recur with troubling regularity and show no sign of abatement. This work uncovers new data-driven findings pertaining to LTE and risk factors. First, a scorecard is developed covering a broad range of results to better understand LTE accidents. Second, the risk of LTE is derived for current helicopters. Third, a Deep Learning model is developed that captures the dependence between LTE risk and helicopter features. A danger zone is discovered in the design space for short tail rotor arm and high tail rotor RPM. The results challenge the prevailing narrative of LTE accidents as mere pilot errors and demonstrate an intrinsic propensity to these accidents is embedded in part in the helicopter design. The findings open the door to new, more effective safety interventions for LTE accident prevention.

Meniscus-Guided 3D Microprinting of Pure Metal-Organic Frameworks with High Gas-Uptake Performance.

Metal-organic frameworks (MOFs) are a promising nanoporous functional material system; however, the practicality of shaping freeform MOF monoliths, while retaining their porosity, remains a challenge. Here, we demonstrate that meniscus-guided three-dimensional (3D) printing can produce pure MOF monoliths with high gas-uptake performance. The method exploits a femtoliter precursor ink meniscus to highly confine and guide supersaturation-driven crystallization in a layer-by-layer manner to print a pure HKUST-1 micro-monolith with a high spatial resolution of <3 µm. The proposed 3D printing technique does not involve rheological additives, binders, or mechanical forces. Thus, the resulting HKUST-1 monolith displays a prominently high Brunauer-Emmett-Teller surface area of 1192 m2/g, which is superior to monoliths produced using other 3D printing approaches. This technique enables both structural design freedom and high material performance in the manufacturing of MOFs for practical use.

One-step elimination of Cr(VI) by catalytic hydrogenation of Cr(VI) and simultaneous Cr(OH)3 recovery on Pt catalysts encapsulated in N-doped mesoporous carbon.

Hexavalent chromium Cr(VI) is a highly toxic heavy metal, which is commonly eliminated by stepwise reduction at acidic pH and precipitation of Cr(OH)3 at alkaline pH. A unique Pt catalyst with Pt particles embedded in the framework of N-doped mesoporous carbon CMK-3 (denoted as Pt@NCMK-3) was designed and fabricated to one-step eliminate Cr(VI) pollution at near neutral pH via simultaneous Cr(VI) reduction by catalytic hydrogenation and Cr(OH)3 recovery. Structural characterization showed that Pt particles of Pt@NCMK-3 were effectively embedded in the carbon rods of NCMK-3. Batch experiments revealed that Pt@NCMK-3 exhibited a higher catalytic activity and stability than other test catalysts. Fixed-bed column reaction results indicated that under the experimental conditions Pt@NCMK-3 had better breakthrough performances than other catalysts. Additionally, after 4 treatment-recovery cycles Pt@NCMK-3 maintained nearly identical breakthrough performance, whereas other catalysts displayed markedly decreased breakthrough bed volumes, reflecting a substantially higher stability of Pt@NCMK-3.

On-Demand, Direct Printing of Nanodiamonds at the Quantum Level.

The quantum defects in nanodiamonds, such as nitrogen-vacancy (NV) centers, are emerging as a promising candidate for nanoscale sensing and imaging, and the controlled placement with respect to target locations is vital to their practical applications. Unfortunately, this prerequisite continues to suffer from coarse positioning accuracy, low throughput, and process complexity. Here, it is reported on direct, on-demand electrohydrodynamic printing of nanodiamonds containing NV centers with high precision control over quantity and position. After thorough characterizations of the printing conditions, it is shown that the number of printed nanodiamonds can be controlled at will, attaining the single-particle level precision. This printing approach, therefore, enables positioning NV center arrays with a controlled number directly on the universal substrate without any lithographic process. The approach is expected to pave the way toward new horizons not only for experimental quantum physics but also for the practical implementation of such quantum systems.

Schwann cells-derived exosomes promote functional recovery after spinal cord injury by promoting angiogenesis.

Exosomes are small vesicles that contain diverse miRNA, mRNA, and proteins that are secreted by multiple cells, and play a vital function in cell-cell communication. Numerous exosomes produced by cells have been demonstrated to be protective against spinal cord injury (SCI). This study aims to investigate the neuroprotective effect of Schwann cells-derived exosomes (SCs-Exos) on spinal cord injury. We found that SCs-Exos can be taken directly by brain-derived endothelial cells.3 (bEnd.3 cells) and promoted to proliferate, migrate, and form bEnd.3 tube. Additionally, our results showed that the pro-angiogenesis molecules, Integrin-ß1, were highly expressed in SCs-Exos. Moreover, we used special shRNA technology to investigate the role of Integrin-ß1 in mediating the effect of SCs-Exos-induced angiogenesis on bEnd.3 cells. We observed that the pro-angiogenic effect of SCs-Exos on bEnd.3 cells was suppressed by inhibiting the expression of integrin-ß1 in SCs-Exos. In the SCI model, we found that SCs-Exos attenuated tissue damage and improved functional recovery after SCI. Using immunofluorescence staining, we observed that SCs-Exos treatment promoted angiogenesis in SCI, and integrin-ß1 was required to promote angiogenesis. In conclusion, our results indicate that SCs-Exos promote angiogenesis by delivering integrin-ß1 and may serve as a promising novel therapeutic agent for enhancing neurological functional recovery after SCI.

Collaborative Allocation and Optimization of Path Planning for Static and Mobile Sensors in Hybrid Sensor Networks for Environment Monitoring and Anomaly Search.

In this study, a novel collaborative method is developed to optimize hybrid sensor networks (HSN) for environmental monitoring and anomaly search tasks. A weighted Gaussian coverage method hs been designed for static sensor allocation, and the Active Monitoring and Anomaly Search System method is adapted to mobile sensor path planning. To validate the network performance, a simulation environment has been developed for fire search and detection with dynamic temperature field and non-uniform fire probability distribution. The performance metrics adopted are the detection time lag, source localization uncertainty, and state estimation error. Computational experiments are conducted to evaluate the performance of HSNs. The results demonstrate that the optimal collaborative deployment strategy allocates static sensors at high-risk locations and directs mobile sensors to patrol the remaining low-risk areas. The results also identify the conditions under which HSNs significantly outperform either only static or only mobile sensor networks in terms of the monitoring performance metrics.

Metal-organic framework-101 grafted with amino groups as solid-phase extraction adsorbent coupled with liquid chromatography for the determination of phenoxycarboxylic acids in environmental samples.

Metal-Organic Framework (MOF) MIL-101 and three amino-modified MIL-101s were synthesized and used as adsorbents for solid-phase extraction of trace-level polar phenoxycarboxylic acids (PCAs) from environmental water samples for quantification by liquid chromatography. The four MOFs were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption-desorption isotherm, pore structure analysis and powder X-ray diffraction analysis. Parameters which play important roles in the process of solid phase extraction were optimized. MIL-101-ethylenediamine (ED) was chosen as the optimum adsorbent for the extraction of PCAs due to electron donation of alkyl groups in aliphatic amino groups and the smaller steric hindrance. The extraction efficiency using MIL-101-ED compacted column was compared with three commercial columns and the influence of humic acid (HA) on extraction was investigated. The merits of newly-built SPE-LC method based on MIL-101-ED are as follows: (a) low limits of detection (0.052-0.160 ng mL-1), (b) wide linear ranges (0.5-1000 ng mL-1), (c) good repeatabilities (1.33-3.35%) and reproducibilities (2.51-3.49%) and (d) excludability of HA. This method has been applied to the determination of PCAs in environmental water samples successfully.