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1.
J Safety Res ; 80: 97-108, 2022 02.
Article in English | MEDLINE | ID: mdl-35249632

ABSTRACT

INTRODUCTION: This study develops an injury severity model that demonstrates level of pedestrians' injury severity during pedestrian-vehicle collisions, specifically those involving distracted driving. METHOD: It uses data from a police-reported collision database that contains pedestrian-vehicle collision information in Nova Scotia, Canada. A latent segmentation-based ordered logit (LSOL) model is developed in this paper that comprehensively examines the influence of built environment characteristics on pedestrian injury severity. It estimates a latent segment allocation model within LSOL modeling framework to capture unobserved heterogeneity across pedestrians. Two latent segments, high- and low-risk segments, are identified probabilistically based on pedestrian characteristics and action, driver action, and collision attributes. RESULTS: Results suggest that higher mixed land-use, transit stop density, length of sidewalk in the collision locations, and collisions occurring near schools yield lower pedestrian injury severity. In contrast, pedestrian-vehicle collisions in arterial roads, curved roads, sloped roads, and roundabouts tend to result in severe injuries. Interactions between distracted driving type and built environment characteristics are examined in this study. For example, using a communication device while driving on straight roads increases likelihood of higher pedestrian injury severity. This study also confirms the existence of heterogeneity across latent segments. For instance, higher percentage of people commuting by walking in the collision areas yield severe pedestrian injury in high-risk segments and lower injury severity in low-risk segments. Practical applications: The findings of this study will assist transportation planners and road safety stakeholders in developing effective and prioritized policies to reduce pedestrian injury severity involving distracted driving incidents.


Subject(s)
Automobile Driving , Distracted Driving , Pedestrians , Wounds and Injuries , Accidents, Traffic , Built Environment , Humans , Walking/injuries
2.
ACS Omega ; 5(35): 22356-22366, 2020 Sep 08.
Article in English | MEDLINE | ID: mdl-32923793

ABSTRACT

Cu-doped Mn3O4 and Mn-doped CuO (CMO@MCO) mixed oxides with isolated phases together with pristine Mn3O4 (MO) and CuO (CO) have been synthesized by a simple solution process for applications in electrochemical supercapacitors. The crystallographic, spectroscopic, and morphological analyses revealed the formation of all of the materials with good crystallinity and purity with the creation of rhombohedral-shaped MO and CMO and a mixture of spherical and rod-shaped CO and MCO nanostructures. The ratio of CMO and MCO in the optimized CMO@MCO was 2:1 with the Cu and Mn dopants percentages of 12 and 15%, respectively. The MO-, CO-, and CMO@MCO-modified carbon cloth (CC) electrodes delivered the specific capacitance (C s) values of 541.1, 706.7, and 997.2 F/g at 5 mV/s and 413.4, 480.5, and 561.1 F/g at 1.3 A/g, respectively. This enhanced C s value of CMO@MCO with an energy density and a power density of 78.0 Wh/kg and 650.0 W/kg, respectively, could be attributed to the improvement of electrical conductivity induced by the dopants and the high percentage of oxygen vacancies. This corroborated to a decrease in the optical band gap and charge-transfer resistance (R ct) of CMO@MCO at the electrode/electrolyte interface compared to those of MO and CO. The net enhancement of the Faradaic contribution induced by the redox reaction of the dopant and improved surface area was also responsible for the better electrochemical performance of CMO@MCO. The CMO@MCO/CC electrode showed high electrochemical stability with a C s loss of only ca. 4.7%. This research could open up new possibilities for the development of doped mixed oxides for high-performance supercapacitors.

3.
J Am Chem Soc ; 142(33): 14102-14116, 2020 08 19.
Article in English | MEDLINE | ID: mdl-32702990

ABSTRACT

Membrane proteins and lipids coevolved to yield unique coregulatory mechanisms. Inward-rectifier K+ (Kir) channels are often activated by anionic lipids endemic to their native membranes and require accessible water along their K+ conductance pathway. To better understand Kir channel activation, we target multiple mutants of the Kir channel KirBac1.1 via solid-state nuclear magnetic resonance (SSNMR) spectroscopy, potassium efflux assays, and Förster resonance energy transfer (FRET) measurements. In the I131C stability mutant (SM), we observe an open-active channel in the presence of anionic lipids with greater activity upon addition of cardiolipin (CL). The introduction of three R to Q mutations (R49/151/153Q (triple Q mutant, TQ)) renders the protein inactive within the same activating lipid environment. Our SSNMR experiments reveal a stark reduction of lipid-protein interactions in the TQ mutant explaining the dramatic loss of channel activity. Water-edited SSNMR experiments further determined the TQ mutant possesses greater overall solvent exposure in comparison to wild-type but with reduced water accessibility along the ion conduction pathway, consistent with the closed state of the channel. These experiments also suggest water is proximal to the selectivity filter of KirBac1.1 in the open-activated state but that it may not directly enter the selectivity filter. Our findings suggest lipid binding initiates a concerted rotation of the cytoplasmic domain subunits, which is stabilized by multiple intersubunit salt bridges. This action buries ionic side chains away from the bulk water, while allowing water greater access to the K+ conduction pathway. This work highlights universal membrane protein motifs, including lipid-protein interactions, domain rearrangement, and water-mediated diffusion mechanisms.


Subject(s)
Lipids/chemistry , Potassium Channels/metabolism , Fluorescence Resonance Energy Transfer , Nuclear Magnetic Resonance, Biomolecular , Potassium Channels/chemistry , Potassium Channels/genetics
4.
Proc Natl Acad Sci U S A ; 117(28): 16363-16372, 2020 07 14.
Article in English | MEDLINE | ID: mdl-32601205

ABSTRACT

The epididymal lumen contains a complex cystatin-rich nonpathological amyloid matrix with putative roles in sperm maturation and sperm protection. Given our growing understanding for the biological function of this and other functional amyloids, the problem still remains: how functional amyloids assemble including their initial transition to early oligomeric forms. To examine this, we developed a protocol for the purification of nondenatured mouse CRES, a component of the epididymal amyloid matrix, allowing us to examine its assembly to amyloid under conditions that may mimic those in vivo. Herein we use X-ray crystallography, solution-state NMR, and solid-state NMR to follow at the atomic level the assembly of the CRES amyloidogenic precursor as it progressed from monomeric folded protein to an advanced amyloid. We show the CRES monomer has a typical cystatin fold that assembles into highly branched amyloid matrices, comparable to those in vivo, by forming ß-sheet assemblies that our data suggest occur via two distinct mechanisms: a unique conformational switch of a highly flexible disulfide-anchored loop to a rigid ß-strand and by traditional cystatin domain swapping. Our results provide key insight into our understanding of functional amyloid assembly by revealing the earliest structural transitions from monomer to oligomer and by showing that some functional amyloid structures may be built by multiple and distinctive assembly mechanisms.


Subject(s)
Amyloid/chemistry , Amyloidogenic Proteins/chemistry , Cystatins/chemistry , Amyloid/metabolism , Amyloid/ultrastructure , Amyloidogenic Proteins/metabolism , Animals , Crystallography, X-Ray , Cystatins/metabolism , Epididymis/metabolism , Magnetic Resonance Spectroscopy , Male , Mice , Models, Molecular , Protein Conformation , Protein Folding , Protein Multimerization
5.
Beilstein J Nanotechnol ; 11: 597-605, 2020.
Article in English | MEDLINE | ID: mdl-32318320

ABSTRACT

Polyaniline-derived carbon (PDC) was obtained via pyrolysis of polyaniline under different temperatures and applied for the purification of water contaminated with dye molecules of different sizes and charge by adsorption. With increasing pyrolysis temperature, it was found that the hydrophobicity, pore size and mesopore volume increased. A mesoporous PDC sample obtained via pyrolysis at 900 °C showed remarkable performance in the adsorption of dye molecules, irrespective of dye charge, especially in the removal of bulky dye molecules, such as acid red 1 (AR1) and Janus green B (JGB). For example, the most competitive PDC material showed a Q 0 value (maximum adsorption capacity) 8.1 times that of commercial, activated carbon for AR1. The remarkable adsorption of AR1 and JGB over KOH-900 could be explained by the combined mechanisms of hydrophobic, π-π, electrostatic and van der Waals interactions.

6.
Proc Natl Acad Sci U S A ; 117(6): 2938-2947, 2020 02 11.
Article in English | MEDLINE | ID: mdl-31980523

ABSTRACT

The conformational changes required for activation and K+ conduction in inward-rectifier K+ (Kir) channels are still debated. These structural changes are brought about by lipid binding. It is unclear how this process relates to fast gating or if the intracellular and extracellular regions of the protein are coupled. Here, we examine the structural details of KirBac1.1 reconstituted into both POPC and an activating lipid mixture of 3:2 POPC:POPG (wt/wt). KirBac1.1 is a prokaryotic Kir channel that shares homology with human Kir channels. We establish that KirBac1.1 is in a constitutively active state in POPC:POPG bilayers through the use of real-time fluorescence quenching assays and Förster resonance energy transfer (FRET) distance measurements. Multidimensional solid-state NMR (SSNMR) spectroscopy experiments reveal two different conformers within the transmembrane regions of the protein in this activating lipid environment, which are distinct from the conformation of the channel in POPC bilayers. The differences between these three distinct channel states highlight conformational changes associated with an open activation gate and suggest a unique allosteric pathway that ties the selectivity filter to the activation gate through interactions between both transmembrane helices, the turret, selectivity filter loop, and the pore helix. We also identify specific residues involved in this conformational exchange that are highly conserved among human Kir channels.


Subject(s)
Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Potassium Channels, Inwardly Rectifying/chemistry , Potassium Channels, Inwardly Rectifying/metabolism , Bacterial Proteins/genetics , Catalytic Domain , Fluorescence Resonance Energy Transfer , Kinetics , Magnetic Resonance Spectroscopy , Models, Molecular , Phosphatidylcholines/chemistry , Phosphatidylcholines/metabolism , Phosphatidylglycerols/chemistry , Phosphatidylglycerols/metabolism , Potassium/metabolism , Potassium Channels, Inwardly Rectifying/genetics , Protein Conformation , Protein Domains , Protein Structure, Secondary
7.
Small ; 16(12): e1901564, 2020 Mar.
Article in English | MEDLINE | ID: mdl-31166653

ABSTRACT

Polyanilines (pANIs), loaded with phosphotungstic acid (PTA), are pyrolyzed to get WO3 or W2 N (≈6 and ≈7 nm, respectively), which is well-dispersed on pANI-derived porous carbons (pDCs). Depending on the pyrolysis temperature, WO3 /pDC, W2 N/pDC, or W2 N-W/pDCs could be obtained selectively. pANI acts as both the precursor of pDC and the nitrogen source for the nitridation of WO3 into W2 N during the pyrolysis. Importantly, W2 N could be obtained from the pyrolysis without ammonia feeding. The obtained W2 N/pDC is applied as a heterogeneous catalyst for the oxidative desulfurization (ODS) of liquid fuel for the first time, and the results are compared with WO3 /pDC and WO3 /ZrO2 . The W2 N/pDC is very efficient in ODS with remarkable performance compared with WO3 /pDC or WO3 /ZrO2 , which is applied as a representative ODS catalyst. For example, W2 N/pDC shows around 3.4 and 2.7 times of kinetic constant and turnover frequency (based on 5 min of reaction), respectively, compared to that of WO3 /ZrO2 . Moreover, the catalysts could be regenerated in a facile way. Therefore, W2 N/pDC could be produced facilely from pyrolysis (without ammonia feeding) of PTA/pANI, and W2 N, well-dispersed on pDC, can be suggested as a very efficient oxidation catalyst for the desulfurization of liquid fuel.

8.
Sci Rep ; 9(1): 9210, 2019 06 25.
Article in English | MEDLINE | ID: mdl-31239483

ABSTRACT

An amyloid matrix composed of several family 2 cystatins, including the reproductive cystatin CRES, is an integral structure in the mouse epididymal lumen and has proposed functions in sperm maturation and protection. Understanding how CRES amyloid assembles in vitro may provide clues on how the epididymal amyloid matrix forms in vivo. We therefore purified full-length CRES under nondenaturing conditions and followed its aggregation from monomer to amyloid under conditions that may approximate those in the epididymal lumen. CRES transitioned into a metastable oligomer that was resistant to aggregation and only over extended time formed higher-ordered amyloids. High protein concentrations facilitated oligomer assembly and also were required to maintain the metastable state since following dilution the oligomer was no longer detected. Similar to other amyloid precursors, the formation of CRES amyloids correlated with a loss of α-helix and a gain of ß-sheet content. However, CRES is unique in that its amyloids are rich in antiparallel ß-sheets instead of the more common parallel ß-sheets. Taken together, our studies suggest that early metastable oligomers may serve as building blocks for functional amyloid assembly and further reveal that antiparallel ß-sheet-rich amyloids can be functional forms.


Subject(s)
Amyloid/chemistry , Cystatins/chemistry , Protein Multimerization , Animals , Epididymis/metabolism , Heat-Shock Response , Male , Mice , Models, Molecular , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Stress, Mechanical
9.
PLoS One ; 14(4): e0214440, 2019.
Article in English | MEDLINE | ID: mdl-31009467

ABSTRACT

The hydrolysis of ß-lactam antibiotics by ß-lactamase enzymes is the most prominent antibiotic resistance mechanism for many pathogenic bacteria. Out of this broad class of enzymes, metallo-ß-lactamases are of special clinical interest because of their broad substrate specificities. Several in vitro inhibitors for various metallo-ß-lactamases have been reported with no clinical efficacy. Previously, we described a 10-nucleotide single stranded DNA aptamer (10-mer) that inhibits Bacillus cereus 5/B/6 metallo-ß-lactamase very effectively. Here, we find that the aptamer shows uncompetitive inhibition of Bacillus cereus 5/B/6 metallo-ß-lactamase during cefuroxime hydrolysis. To understand the mechanism of inhibition, we report a 2.5 Å resolution X-ray crystal structure and solution-state NMR analysis of the free enzyme. Chemical shift perturbations were observed in the HSQC spectra for several residues upon titrating with increasing concentrations of the 10-mer. In the X-ray crystal structure, these residues are distal to the active site, suggesting an allosteric mechanism for the aptamer inhibition of the enzyme. HADDOCK molecular docking simulations suggest that the 10-mer docks 26 Å from the active site. We then mutated the three lysine residues in the basic binding patch to glutamine and measured the catalytic activity and inhibition by the 10-mer. No significant inhibition of these mutants was observed by the 10-mer as compared to wild type. Interestingly, mutation of Lys50 (Lys78; according to standard MBL numbering system) resulted in reduced enzymatic activity relative to wild type in the absence of inhibitor, further highlighting an allosteric mechanism for inhibition.


Subject(s)
Anti-Bacterial Agents/pharmacology , Aptamers, Nucleotide/chemistry , beta-Lactamase Inhibitors/pharmacology , beta-Lactamases/metabolism , Allosteric Site , Bacillus cereus/drug effects , Bacillus cereus/enzymology , Catalysis , Catalytic Domain , Crystallography, X-Ray , Kinetics , Magnetic Resonance Spectroscopy , Molecular Docking Simulation , Mutagenesis, Site-Directed , Protein Binding , Substrate Specificity , beta-Lactamases/genetics
10.
ACS Appl Mater Interfaces ; 10(41): 35639-35646, 2018 Oct 17.
Article in English | MEDLINE | ID: mdl-30256614

ABSTRACT

Polyaniline-encapsulated metal-organic frameworks (MOFs; MIL-101, Cr-benzenedicarboxylate) were prepared via a ship-in-bottle strategy and applied in liquid phase adsorptions. The modified MIL-101s showed record-high adsorptions for both basic and neutral nitrogen-containing compounds (NCCs) from liquid model fuel. For example, the maximum adsorption capacities ( Qo) of the protonated polyaniline (pANI)@MIL-101 for the basic quinoline and neutral indole from n-octane were 556 and 602 mg/g, respectively. The plausible adsorption mechanisms such as hydrogen bonding, acid-base interaction, and cation-π interaction were proposed to explain the extraordinary adsorptions of the studied adsorbates. Moreover, the adsorbents could be recycled via a simple approach and reused in adsorptions without noticeable decrease in performances. Therefore, the pANI-encapsulated MOFs could be recommended as a new type of adsorbents for very efficient removal of both basic and neutral NCCs from liquid fuel.

11.
J Hazard Mater ; 360: 163-171, 2018 10 15.
Article in English | MEDLINE | ID: mdl-30099359

ABSTRACT

Polyaniline (pANI) was pyrolyzed under a nitrogen atmosphere to get porous pANI-derived carbons (PDCs). To increase the porosity of the carbons further, the PDCs were activated at 600-800 °C in the presence of KOH. The obtained PDCs were firstly applied in liquid-phase adsorptions in order to remove hazardous organics from both water and fuel effectively via adsorption. PDC-700, activated at 700 °C, showed record high adsorption capacities from water for the removal of hazardous organics such as diethyl phthalate and Janus Green B, as representative organics for industrial chemicals (endocrine disturbing agent) and organic dyes, respectively. Moreover, PDC-700 had record high adsorption capacity for the removal of 4,6-dimethyldibenzothiophene from a model fuel. The plausible mechanisms were also suggested to explain the remarkable adsorptions both from water and fuel. The adsorbents could be regenerated in a facile way and reused in adsorption up to several cycles. Therefore, the PDCs could be suggested as a new class of adsorbents for the purification of both water contaminated with organics and fuel having a high concentration of thiophenics.

12.
ACS Appl Mater Interfaces ; 9(36): 31192-31202, 2017 Sep 13.
Article in English | MEDLINE | ID: mdl-28820235

ABSTRACT

A new metal-organic framework (MOF) composite consisting of Ti- and Zn-based MOFs (ZIF-8(x)@H2N-MIL-125; in brief, ZIF(x)@MOF) was designed and synthesized. The pristine MOF [H2N-MIL-125 (MOF)]- and an MOF-composite [ZIF(30)@MOF]-derived mesoporous carbons consisting of TiO2 nanoparticles were prepared by pyrolysis (named MDC-P and MDC-C, respectively). MDC-C showed a higher surface area, larger pore sizes, and larger mesopore volumes than MDC-P. In addition, the TiO2 nanoparticles on MDC-C have more uniform shapes and sizes and are smaller than those of MDC-P. The obtained MDC-C and MDC-P [together with MOF, ZIF(30)@MOF, pure/nanocrystalline TiO2, and activated carbon] were applied in the oxidative desulfurization reaction of dibenzothiophene in a model fuel. The MDC-C, even with a lower TiO2 content than that of MDC-P, showed an outstanding catalytic performance, especially with a very low catalyst dose (i.e., a very high quantity of dibenzothiophene was converted per unit weight of the catalyst), fast kinetics (∼3 times faster than that for MDC-P), and a low activation energy (lower than that for any reported catalyst) for the oxidation of dibenzothiophene. The large mesopores of MDC-C and the well-dispersed/small TiO2 might be the dominant factors for the superior catalytic conversions. The oxidative desulfurization of other sulfur-containing organic compounds with various electron densities was also studied with MDC-C to understand the mechanism of catalysis. Moreover, the MDC-C catalyst can be reused many times in the oxidative desulfurization reaction after a simple washing with acetone. Finally, composing MOFs and subsequent pyrolysis is suggested as an effective way to prepare a catalyst with well-dispersed active sites, large pores, and high mesoporosity.

13.
ACS Appl Mater Interfaces ; 9(24): 20938-20946, 2017 Jun 21.
Article in English | MEDLINE | ID: mdl-28569501

ABSTRACT

The removal of nitrogen-containing compounds (NCCs) from fossil fuels prior to combustion is currently of particular importance, and so we investigated an adsorptive method using metal-organic frameworks (MOFs) for the removal of indole (IND) and quinoline (QUI), which are two of the main NCCs present in fossil fuels. We herein employed an amino (-NH2)-functionalized MIL-125 (MIL-125-NH2) MOF, which was further modified by protonation (P-MIL-125-NH2). These modified MOFs exhibited extraordinary performance in the adsorption of both IND (as representative neutral NCC) and QUI (as representative basic NCC). These MOFs were one of the most efficient adsorbents for the removal of NCCs. For example, P-MIL-125-NH2 showed the highest adsorption capacity for QUI among ever reported adsorbent. The improved adsorption of IND was explained by H-bonding and cation-π interactions for MIL-125-NH2 and P-MIL-125-NH2, respectively, while the mechanisms for QUI were H-bonding and acid-base interactions, respectively. This is a rare phenomenon for a single material (especially not with very high porosity) to exhibit such remarkable performances in the adsorption of both basic QUI and neutral IND. The adsorption results obtained using regenerated MIL-125-NH2 and P-MIL-125-NH2 also showed that these materials can be used several times without any severe degradation.

14.
ACS Appl Mater Interfaces ; 9(11): 10276-10285, 2017 Mar 22.
Article in English | MEDLINE | ID: mdl-28240863

ABSTRACT

Porous carbons were prepared from a metal-organic framework (MOF, named ZIF-8), with or without modification, via high-temperature pyrolysis. Porous carbons with high nitrogen content were obtained from the calcination of MOF after introducing an ionic liquid (IL) (IL@MOF) via the ship-in-bottle method. The MOF-derived carbons (MDCs) and IL@MOF-derived carbons (IMDCs) were characterized using various techniques and used for liquid-phase adsorptions in both water and hydrocarbon to understand the possible applications in purification of water and fuel, respectively. Adsorptive performances for the removal of organic contaminants, atrazine (ATZ), diuron, and diclofenac, were remarkably enhanced with the modification/conversion of MOFs to MDC and IMDC. For example, in the case of ATZ adsorption, the maximum adsorption capacity of IMDC (Q0 = 208 m2/g) was much higher than that of activated carbon (AC, Q0 = 60 m2/g) and MDC (Q0 = 168 m2/g) and was found to be the highest among the reported results so far. The results of adsorptive denitrogenation and desulfurization of fuel were similar to that of water purification. The IMDCs are very useful in the adsorptions since these new carbons showed remarkable performances in both the aqueous and nonaqueous phases. These results are very meaningful because hydrophobic and hydrophilic adsorbents are usually required for the adsorptions in the water and fuel phases, respectively. Moreover, a plausible mechanism, H-bonding, was also suggested to explain the remarkable performance of the IMDCs in the adsorptions. Therefore, the IMDCs derived from IL@MOF might have various applications, especially in adsorptions, based on high porosity, mesoporosity, doped nitrogen, and functional groups.

15.
J Hazard Mater ; 325: 198-213, 2017 Mar 05.
Article in English | MEDLINE | ID: mdl-27936401

ABSTRACT

Efficient removal and separation of chemicals from the environment has become a vital issue from a biological and environmental point of view. Currently, adsorptive removal/separation is one of the most promising approaches for cleaning purposes. Selective adsorption/removal of various sulfur- and nitrogen-containing compounds, olefins, and π-electron-rich gases via π-complex formation between an adsorbent and adsorbate molecules is very competitive. Porous metal-organic framework (MOF) materials are very promising in the adsorption/separation of various liquids and gases owing to their distinct characteristics. This review summarizes the literature on the adsorptive removal/separation of various π-electron-rich compounds mainly from fuel and gases using MOF materials containing metal ions that are active for π-complexation. Details of the π-complexation, including mechanism, pros/cons, applications, and efficient ways to form the complex, are discussed systematically. For in-depth understanding, molecular orbital calculations regarding charge transfer between the π-complexing species are also explained in a separate section. From this review, readers will gain an understanding of π-complexation for adsorption and separation, especially with MOFs, to develop new insight for future research.

16.
Sci Rep ; 6: 34462, 2016 10 03.
Article in English | MEDLINE | ID: mdl-27695005

ABSTRACT

Adsorption of typical pharmaceuticals and personal care products (PPCPs) (such as naproxen, ibuprofen and oxybenzone) from aqueous solutions was studied by using the highly porous metal-organic framework (MOF) MIL-101 with and without functionalization. Adsorption results showed that MIL-101s with H-donor functional groups such as -OH and -NH2 were very effective for naproxen adsorption, despite a decrease in porosity, probably because of H-bonding between O atoms on naproxen and H atoms on the adsorbent. For this reason, MIL-101 with two functional groups capable of H-bonding (MIL-101-(OH)2) exhibited remarkable adsorption capacity based on adsorbent surface area. The favorable contributions of -OH and -(OH)2 on MIL-101 in the increased adsorption of ibuprofen and oxybenzone (especially based on porosity) confirmed again the importance of H-bonding mechanism. The adsorbent with the highest adsorption capacity, MIL-101-OH, was very competitive when compared with carbonaceous materials, mesoporous materials, and pristine MIL-101. Moreover, the MIL-101-OH could be recycled several times by simply washing with ethanol, suggesting potential application in the adsorptive removal of PPCPs from water.


Subject(s)
Benzophenones/chemistry , Ibuprofen/chemistry , Naproxen/chemistry , Wastewater/chemistry , Water Purification/methods , Adsorption , Humans , Hydrogen Bonding
17.
ACS Appl Mater Interfaces ; 8(43): 29799-29807, 2016 Nov 02.
Article in English | MEDLINE | ID: mdl-27723294

ABSTRACT

A highly porous metal-organic framework (MOF), MIL-101, was modified to introduce urea or melamine via grafting on open metal sites of the MOF. Adsorptive removal of three artificial sweeteners (ASWs) was studied using the MOFs, with or without modifications (including nitration), and activated carbon (AC). The adsorbed quantities (based on the weight of the adsorbent) of saccharin (SAC) under various conditions decreased in the order urea-MIL-101 > melamine-MIL-101 > MIL-101 > AC > O2N-MIL-101; however, the quantities based on unit surface area are in the order melamine-MIL-101 > urea-MIL-101 > MIL-101 > O2N-MIL-101. Similar ASWs [acesulfame (ACE) and cyclamate (CYC)] showed the same tendency. The mechanism for very favorable adsorption of SAC, ACE, and CYC over urea- and melamine-MIL-101 could be explained by H-bonding on the basis of the contents of -NH2 groups on the MOFs and the adsorption results under a wide range of pH values. Moreover, the direction of H-bonding could be clearly defined (H acceptor: ASWs; H donor: MOFs). Urea-MIL-101 and melamine-MIL-101 could be suggested as competitive adsorbents for organic contaminants (such as ASWs) with electronegative atoms, considering their high adsorption capacity (for example, urea-MIL-101 had 2.3 times the SAC adsorption of AC) and ready regeneration.

18.
Inorg Chem ; 55(21): 11362-11371, 2016 Nov 07.
Article in English | MEDLINE | ID: mdl-27763765

ABSTRACT

Two highly porous Co-based metal-azolate frameworks (MAFs), MAF-5(Co) and MAF-6(Co), which are isostructural with MAF-5(Zn) and MAF-6(Zn), respectively, were first synthesized in high yield and purity at room temperature. The syntheses compared two mixing methods, slow and fast, using cobalt acetate as the metal ion (Co2+) source and 2-ethylimidazole as the ligand. Triethylamine was applied as an additive/promoter in aqueous/ethanol solutions, and benzene and cyclohexane were used as hydrophobic templates. Phase-pure MAF-5(Co) and MAF-6(Co) were obtained in high yield by optimizing the mixing speed, reactant composition, and solvent/template ratio. It was found that fast mixing of the reactant mixtures was effective for synthesizing MAF(Co) materials. MAF-5(Co) and MAF-6(Co) were found to be very hydrophobic, similar to the MAFs composed of Zn, suggesting possible applications in water purification. MAF-5(Co) and MAF-6(Co) were then applied to adsorb n-octane as a model oil and nonpolar adsorbate from water, and the obtained results were compared to those of related materials, i.e., MAF-4(Co and Zn), MAF-5(Zn), and MAF-6(Zn), as well as with Cu-BTC (Cu-benzenetricarboxylate) and a conventional adsorbent, activated carbon. Surprisingly, despite having low porosity, MAF-5(Co) showed remarkable competitiveness among the typical porous materials for n-octane removal. The results suggest that the framework structure such as cavity and aperture sizes rather than surface area plays a significant role in n-octane removal. Moreover, MAF-5(Co) can easily be regenerated by simple evacuation and reused, and thus it was found to be a potential adsorbent for the removal of spilled oil from water. Additionally, MAFs were applied in the adsorption of diclofenac sodium from water, showing the competitiveness of MAFs in water purification probably because of hydrophobicity.

19.
Chem Commun (Camb) ; 52(56): 8667-70, 2016 Jul 05.
Article in English | MEDLINE | ID: mdl-27284597

ABSTRACT

Several metal-organic frameworks (MOFs) were employed in adsorptive desulfurization in the presence of oxygen-containing compounds (OCCs). Unlike conventional MOFs and activated carbon, flexible MOFs with a MIL-53 topology showed remarkable performances for the desulfurization in the presence of OCCs.

20.
Chem Commun (Camb) ; 52(12): 2561-4, 2016 Feb 11.
Article in English | MEDLINE | ID: mdl-26744746

ABSTRACT

Ionic liquids (ILs) were synthesized inside a porous metal-organic framework (MIL-101) via a ship-in-bottle (SIB) technique. Unlike previously reported IL-incorporated MIL-101s, IL@MIL-101 prepared by the SIB approach was very stable over several cycles for the liquid phase adsorption of benzothiophene from liquid fuel.

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