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Membrane technology plays a central role in advancing separation processes, particularly in water treatment. Covalent organic frameworks (COFs) have transformative potential in this field due to their adjustable structures and robustness. However, conventional COF membrane synthesis methods are often associated with challenges, such as time-consuming processes and limited control over surface properties. Our study demonstrates a rapid, microwave-assisted method to synthesize self-standing COF membranes within minutes. This approach allows control over the wettability of the surface and achieves superhydrophilic and near-hydrophobic properties. A thorough characterization of the membrane allows a detailed analysis of the membrane properties and the difference in wettability between its two faces. Microwave activation accelerates the self-assembly of the COF nanosheets, whereby the thickness of the membrane can be controlled by adjusting the time of the reaction. The superhydrophilic vapor side of the membrane results from -NH2 reactions with acetic acid, while the nearly hydrophobic dioxane side has terminal aldehyde groups. Leveraging the superhydrophilic face, water filtration at high water flux, complete oil removal, increased rejection with anionic dye size, and resistance to organic fouling were achieved. The TTA-DFP-COF membrane opens new avenues for research to address the urgent need for water purification, distinguished by its synthesis speed, simplicity, and superior separation capabilities.
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Visual sensing of humidity and temperature by solids plays an important role in the everyday life and in industrial processes. Due to their hydrophobic nature, most covalent organic framework (COF) sensors often exhibit poor optical response when exposed to moisture. To overcome this challenge, the optical response is set out to improve, to moisture by incorporating H-bonding ionic functionalities into the COF network. A highly sensitive COF, consisting of guanidinium and diformylpyridine linkers (TG-DFP), capable of detecting changes in temperature and moisture content is fabricated. The hydrophilic nature of the framework enables enhanced water uptake, allowing the trapped water molecules to form a large number of hydrogen bonds. Despite the presence of non-emissive building blocks, the H-bonds restrict internal bond rotation within the COF, leading to reversible fluorescence and solid-state optical hydrochromism in response to relative humidity and temperature.
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Stimuli-responsive chromic materials such as photochromics, hydrochromics, thermochromics, and electrochromics have a long history of capturing the attention of scientists due to their potential industrial applications and novelty in popular culture. However, hybrid chromic materials that combine two or more stimuli-triggered color changing properties are not so well known. Herein, we report a design strategy that has led to a series of emissive 1,8-naphthalimide-viologen dyads which exhibit unusual dual photochromic and hydrochromic switching behavior in the solid-state when embedded in a cellulose matrix. This behavior manifests as reversible solid state fluorescence hydrochromism upon changes in atmospheric relative humidity (RH), and reversible solid state photochromism upon generation of a cellulose-stabilized viologen radical cation. In this design strategy, the bipyridinium unit serves as both a water-sensitive receptor for the hydrochromic fluorophore-receptor system, and a photochromic group, capable of eliciting its own visible colorimetric response, generating a fluorescence quenching radical cation with prolonged exposure to ultraviolet (UV) light. These dyes can be inkjet-printed onto cellulose paper or drop-cast as cellulose powder-based films and can be unidirectionally cycled between three different states which can be characteristically visualized under UV light or visible light. The material's photochromism, hydrochromism, and underlying mechanism of action was investigated using computational analysis, dynamic vapor sorption/desorption isotherms, electron paramagnetic resonance spectroscopy, and variable humidity UV-Vis adsorption and fluorescence spectroscopies.
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Naftalimidas , Viologênios , Celulose , Luz , Raios UltravioletaRESUMO
Silica-supported hierarchical graphitic carbon sheltering cobalt nanoparticles Co-HGC@SiO2 (1) were prepared by pyrolysis at 850 °C of [Co(phen)(H2O)4]SO4·2H2O complex with silica in the presence of pyrene as a carbon source under nitrogen atmosphere. Nanocomposites (2) and (3) were obtained by acid treatment of (1) with HCl and HF acid, respectively. The nanocomposites showed rough hierarchical carbon microstructures over silica support decorated with irregular cobalt nanospheres and nanorods 50 to 200 nm in diameter. The nanoparticles consist of graphitic shells and cobalt cores. SEM, EDAX and TEM elemental mapping indicate a noticeable loss of cobalt in the case of (2) and loss of cobalt and silica in the case of (3) with an increase in porosity. Nanocomposite (3) showed the highest BET surface area 217.5 m2g-1. Raman spectrum shows defect D-band and graphitic G-band as expected in carbon nanostructures. PXRD reveals the presence of cobalt(0) nanoparticles. XPS indicates the presence of Co(II) oxides and the successful doping of nitrogen in the nanocomposites. Moreover, TEM elemental mapping provides information about the abundance of Si, Co, C, N and S elements in zones. Nanocomposite (1) showed maximum uptake capacity of 192.3 and 224.5 mg/g for crystal violet CV and methyl orange MO dyes, respectively. Nanocomposite (2) showed a capacity of 94.1 and 225.5 mg/g for CV and MO dyes, respectively. Nanocomposite (4) obtained after treatment of (1) with crystal violet proved successful adsorption of CV. Co-HGC (5) prepared without addition of silica has a capacity for CV equal to 192 mg/g, while it is 769.2 mg/g with MO. Electrostatics and π-π interactions of graphite and cobalt species in the nanocomposites with aromatic rings of cationic and anionic dyes are responsible for the adsorption. Yan et al. was the best model to describe column kinetics. The thomas column adsorption model showed that the maximum uptake capacity of (1) was 44.42 mg/g for CV and 32.62 mg/g for MO. for a column packed with 0.5 gm of (1) and dye concentration of 100 mg/L at a flow rate of 1 mL/min. The column was recycled three times with no noticeable clogging or degradation of nanocomposites. Thus, Co-HGC@SiO2 adsorbents can be used efficiently to treat water contaminated with cationic and anionic dyes.
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Nanoscale imine-linked covalent organic frameworks (nCOFs) were first loaded with the anticancer drug Doxorubicin (Dox), coated with magnetic iron oxide nanoparticles (γ-Fe2O3 NPs), and stabilized with a shell of poly(l-lysine) cationic polymer (PLL) for simultaneous synergistic thermo-chemotherapy treatment and MRI imaging. The pH responsivity of the resulting nanoagents (γ-SD/PLL) allowed the release of the drug selectively within the acidic microenvironment of late endosomes and lysosomes of cancer cells (pH 5.4) and not in physiological conditions (pH 7.4). γ-SD/PLL could efficiently generate high heat (48 °C) upon exposure to an alternating magnetic field due to the nCOF porous structure that facilitates the heat conduction, making γ-SD/PLL excellent heat mediators in an aqueous solution. The drug-loaded magnetic nCOF composites were cytotoxic due to the synergistic toxicity of Dox and the effects of hyperthermia in vitro on glioblastoma U251-MG cells and in vivo on zebrafish embryos, but they were not significantly toxic to noncancerous cells (HEK293). To the best of our knowledge, this is the first report of multimodal MRI probe and chemo-thermotherapeutic magnetic nCOF composites.
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Compostos Férricos/química , Iminas/química , Nanopartículas de Magnetita/química , Nanopartículas/química , Animais , Antineoplásicos/química , Antineoplásicos/metabolismo , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Doxorrubicina/química , Doxorrubicina/metabolismo , Doxorrubicina/farmacologia , Portadores de Fármacos/química , Embrião não Mamífero/efeitos dos fármacos , Células HEK293 , Humanos , Concentração de Íons de Hidrogênio , Hipertermia Induzida , Imageamento por Ressonância Magnética , Polilisina/química , Porosidade , Temperatura , Peixe-Zebra/crescimento & desenvolvimentoRESUMO
Triphenylphosphine (TPP) surface-functionalized and F-108 Pluronic-stabilized gold nanoparticles (F-108@TPP-AuNPs) have been synthesized through a one-step approach, leading to well-defined (9.6±1.6â nm) and water-soluble nanoparticles by microwave heating an aqueous solution of TPP-AuI Cl in the presence of a Pluronic polymer under basic conditions. TPP release was negligible under physiological conditions, but enhanced significantly at an acidic pH (5.4) mimicking that of a cancer cell. Laser irradiation (532â nm) raised the temperature of an aqueous solution of F-108@TPP-AuNPs to 51.7 °C within 5â min, confirming efficient light-to-heat conversion capabilities without significant photodegradation. TEM confirmed intracellular localization of F-108@TPP-AuNPs in the cytosol, endosomes and lysosomes of HeLa cells. F-108@TPP-AuNPs were well tolerated by HeLa cells and zebrafish embryos at ambient temperatures and became toxic upon heat activation, suggesting synergistic interactions between heat and cytotoxic action by TPP.
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Antineoplásicos/farmacologia , Ouro/química , Nanopartículas Metálicas/química , Compostos Organofosforados/química , Antineoplásicos/química , Células HeLa , Humanos , Fototerapia , Polímeros/química , TemperaturaRESUMO
Light-operated materials have gained significant attention for their potential technological importance. To achieve molecular motion within extended networks, stimuli-responsive units require free space. The majority of the so far reported 2D-extended organic networks with responsive moieties restrict their freedom of motion on account of their connectivity providing constrained free volume for efficient molecular motion. We report here a light-responsive azobenzene-functionalized covalent organic framework (TTA-AzoDFP) designed in a way that the pendent azobenzene groups are pointing toward the pore channels with sufficient free volume necessary for the unencumbered dynamic motion to occur inside the pores of the covalent organic framework (COF) and undergo a reversible trans-cis photoisomerization upon light irradiation. The resulting hydrophobic COF was used for the storage of rhodamine B and its controlled release in solution by the mechanical motion of the azobenzene units triggered by ultraviolet-light irradiation. The TTA-AzoDFP displayed unprecedented photoregulated fluorescence emission behavior upon UV-light irradiation. Size, emission, and degree of hydrophobicity with respect to trans-cis-trans photoisomerization could be reversibly controlled by alternating UV- and visible-light exposure. The results reported here demonstrate once again the importance of the careful design of the linkers not only to allow the incorporation of molecular switches within the chemical structure of COFs but also to provide the required free space for not hindering their motion. The results demonstrate that responsive COFs could be suitable platforms for delivery systems that can be controlled by external stimuli.
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Suppression of the dimerization of the viologen radical cation by cucurbit[7]uril (CB7) in water is a well-known phenomenon. Herein, two counter-examples are presented. Two viologen-containing thread molecules were designed, synthesized, and thoroughly characterized by (1)H DOSY NMR spectrometry, UV/Vis absorption spectrophotometry, square-wave voltammetry, and chronocoulometry: BV(4+), which contains two viologen subunits, and HV(12+), which contains six. In both threads, the viologen subunits are covalently bonded to a hexavalent phosphazene core. The corresponding [3]- and [7]pseudorotaxanes that form on complexation with CB7, that is, BV(4+)â(CB7)2 and HV(12+)â(CB7)6, were also analyzed. The properties of two monomeric control threads, namely, methyl viologen (MV(2+)) and benzyl methyl viologen (BMV(2+)), as well as their [2]pseudorotaxane complexes with CB7 (MV(2+)âCB7 and BMV(2+)âCB7) were also investigated. As expected, the control pseudorotaxanes remained intact after one-electron reduction of their viologen-recognition stations. In contrast, analogous reduction of BV(4+)â(CB7)2 and HV(12+)â(CB7)6 led to host-guest decomplexation and release of the free threads BV(2(·+)) and HV(6(·+)), respectively. (1)H DOSY NMR spectrometric and chronocoulometric measurements showed that BV(2(·+)) and HV(6(·+)) have larger diffusion coefficients than the corresponding [3]- and [7]pseudorotaxanes, and UV/Vis absorption studies provided evidence for intramolecular radical-cation dimerization. These results demonstrate that radical-cation dimerization, a relatively weak interaction, can be used as a driving force in novel molecular switches.
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Rotaxanos/síntese química , Cátions , Dimerização , Modelos Moleculares , Estrutura Molecular , Rotaxanos/químicaRESUMO
In view of the increasing global demand and consumption of gold, there is a growing need and effort to extract gold from alternative sources besides conventional mining, e.g., from water. This drive is mainly due to the potential benefits for the economy and the environment as these sources contain large quantities of the precious metal that can be utilized. Wastewater is one of these valuable sources in which the gold concentration can be in the ppb range. However, the effective selective recovery and recycling of ultratrace amounts of this metal remain a challenge. In this article, we describe the development of a covalent imine-based organic framework with pores containing thioanisole functional groups (TTASDFPs) formed by the condensation of a triazine-based triamine and an aromatic dialdehyde. The sulfur-functionalized pores served as effective chelating agents to bind Au3+ ions, as evidenced by the uptake of more than 99% of the 9 ppm Au3+ solution within 2 min. This is relatively fast kinetics compared with other adsorbents reported for gold adsorption. TTASDFP also showed a high removal capacity of 245 mg·g-1 and a clear selectivity toward gold ions. More importantly, the material can capture gold at concentrations as low as 1 ppb.
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A topological triptych: Three molecular links, a [2]catenane, a trefoil knot, and a Solomon link, were obtained in one pot through the self-assembly of two simple ligands in the presence of Zn(II). The approach relied on dynamic covalent chemistry and metal templation.
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Catenanos/química , Ligantes , Modelos Moleculares , Estrutura Molecular , Conformação Proteica , Dobramento de Proteína , Estrutura Secundária de ProteínaRESUMO
Controlling the number of molecular switches and their relative positioning within porous materials is critical to their functionality and properties. The proximity of many molecular switches to one another can hinder or completely suppress their response. Herein, a synthetic strategy involving mixed linkers is used to control the distribution of spiropyran-functionalized linkers in a covalent organic framework (COF). The COF contains a spiropyran in each pore which exhibits excellent reversible photoswitching behavior to its merocyanine form in the solid state in response to UV/Vis light. The spiro-COF possesses an urchin-shaped morphology and exhibits a morphological transition to 2D nanosheets and vesicles in solution upon UV light irradiation. The merocyanine-equipped COFs are extremely stable and possess a more ordered structure with enhanced photoluminescence. This approach to modulating structural isomerization in the solid state is used to develop inkless printing media, while the photomediated polarity change is used for water harvesting applications.
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Síndrome de Cockayne , Estruturas Metalorgânicas , Humanos , Nitrocompostos , PorosidadeRESUMO
Ionic covalent organic frameworks (iCOFs) are new examples of porous materials and have shown great potential for various applications. When functionalized with suitable emission sites, guest uptake via the ionic moieties of iCOFs can cause a significant change in luminescence, making them excellent candidates for chemosensors. In here, we present a luminescence sensor in the form of an ionic covalent organic framework (TGH+â¢PD) composed of guanidinium and phenanthroline moieties for the detection of ammonia and primary aliphatic amines. TGH+â¢PD exhibits strong emission enhancement in the presence of selective primary amines due to the suppression of intramolecular charge transfer (ICT) with an ultra-low detection limit of 1.2 × 10â7 M for ammonia. The presence of ionic moieties makes TGH+â¢PD highly dispersible in water, while deprotonation of the guanidinium moiety by amines restricts its ICT process and signals their presence by enhanced fluorescence emission. The presence of ordered pore walls introduces size selectivity among analyte molecules, and the iCOF has been successfully used to monitor meat products that release biogenic amine vapors upon decomposition due to improper storage.
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Estruturas Metalorgânicas , Amônia , Aminas Biogênicas , Cátions , Fluorescência , GuanidinaRESUMO
With diabetes being the 7th leading cause of death worldwide, overcoming issues limiting the oral administration of insulin is of global significance. The development of imine-linked-covalent organic framework (nCOF) nanoparticles for oral insulin delivery to overcome these delivery barriers is herein reported. A gastro-resistant nCOF was prepared from layered nanosheets with insulin loaded between the nanosheet layers. The insulin-loaded nCOF exhibited insulin protection in digestive fluids in vitro as well as glucose-responsive release, and this hyperglycemia-induced release was confirmed in vivo in diabetic rats without noticeable toxic effects. This is strong evidence that nCOF-based oral insulin delivery systems could replace traditional subcutaneous injections easing insulin therapy.
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A 3D hierarchical graphitic carbon nanostructure encapsulating cobalt(0)/cobalt oxide nanoparticles (CoGC) has been prepared by solid-state pyrolysis of a mixture of anthracene and cobalt 2,2'-bipyridine terephthalate complex at 850 °C. Based on the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods, the prepared material has high surface area (186.8 m2 g-1) with an average pore width of 205.5 Å. XPS reveals the functionalization of carbon with different oxygen-containing groups, such as carboxylic acid groups. The presence of metallic cobalt nanoparticles with cubic and hexagonal crystalline structures encapsulated in graphitized carbon is confirmed using XRD and TEM. Raman spectroscopy indicates a graphitization degree of I D/I G = 1.02. CoGC was cast onto a glassy carbon electrode and used for urea electrooxidation in an alkaline solution. The electrochemical investigation shows that the newly prepared CoGC has a promising electrocatalytic activity toward urea. The specific activity is 128 mA cm-1 mg-1 for the electrooxidation of 0.3 M urea in 1 M KOH at a relatively low onset potential (0.31 V vs Ag/AgCl). It can be mainly attributed to the morphological structure of carbon and the high reactivity of cobalt nanoparticles. The calculated charge-transfer resistance, R ct, of the modified electrode in the presence of urea (10.95 Ω) is significantly lower than that in the absence of urea (113.5 Ω), which indicates electrocatalytic activity. The value of charge-transfer rate constant, k s, for the anodic reaction is 0.0058 s-1. Electrocatalytic durability in 1000 s chronoamperometry of the modified electrode suggests high structure stability. The modified electrode retained about 60% of its activity after 100 cycles as indicated by linear sweep voltammetry.
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Recently, carbon nanostructures are of high importance due to their unique characteristics and interesting applications. Pyrolysis of anthracene with cobalt complex Co(2,2'-bipy)Cl2 (1), where (2,2'-bipy) is 2,2'-bipyridine, in the absence and presence of silica gave in high yield cobalt-carbon nanocomposite CoCNC (2) and CoCNC@SiO2 (3) at 600 °C and 850 °C, respectively. They were characterized using SEM, TEM, PXRD, Raman and XPS. (3) and (2) contain core-shell cobalt(0)/cobalt oxide-graphite with or without silica support. PXRD indicates that (2) contains crystalline hexagonal α-Co and cubic ß-Co phases while (3) contains only cubic ß-Co phase and silica. The structure of (2) is 3D hierarchical carbon architecture wrapping spherical and elliptical cobalt nanoparticles. (3) consists of graphitized structures around cobalt nanoparticles embedded in the silica matrix. XPS reveals that the nanocomposites contain oxygen functional groups that enhance uptake of cationic dyes. CoCNC@SiO2 (3) has higher capacity and thus is better adsorbent of Basic Violet 3 than CoCNC (2). The Langmuir adsorption capacity of (3) is 19.4 mg g-1 while column capacity is 12.55 mg g-1 at 25 °C. Freundlich isotherm and pseudo-second-order kinetic models fit well the adsorption data. Thermodynamics indicate that adsorption(3) is exothermic. Column regeneration was tested for three cycles and Yan et al. was found the best kinetic model.
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Recently, carbon nanostructures have attracted interest because of their unique properties and interesting applications. Here, CoC@SiO2-850 (3) and CoC@SiO2-600 (4) cobalt-carbon/silica nanocomposites were prepared by solid-state pyrolysis of anthracene with Co(tph)(2,2'-bipy)·4H2O (1) complex in the presence of silica at 850 and 600 °C, respectively, where 2,2'-bipy is 2,2'-bipyridine and tph is the terephthalate dianion. Moreover, Co(µ-tph)(2,2'-bipy) (2) was isolated and its X-ray structure indicated that cobalt(ii) has a distorted trigonal prismatic coordination geometry. 2 is a metal-organic framework consisting of one-dimensional zigzag chains within a porous grid network. 3 and 4 consist of cobalt(0)/cobalt oxide nanoparticles with a graphitic shell and carbon nanotubes embedded in the silica matrix. They were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS revealed that the nanocomposites are functionalized with oxygen-containing groups, such as carboxylic acid groups. In addition, the presence of metallic cobalt nanoparticles embedded in graphitized carbon was verified by XRD and TEM. The efficiency of 3 for adsorption of crystal violet (CV) dye was investigated by batch and column experiments. At 25 °C, the Langmuir adsorption capacity of 3 for CV was 214.2 mg g-1 and the fixed-bed column capacity was 36.3 mg g-1. The adsorption data were well fitted by the Freundlich isotherm and pseudo-second-order kinetic model. The adsorption process was spontaneous and endothermic.
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A set of metal-organic trefoil knots (M-TKs) generated by metal-templated self-assembly of a simple pair of chelating ligands were well tolerated in vitro by non-cancer cells but were significantly more potent than cisplatin in both human cancer cells--including those resistant to cisplatin--and in zebrafish embryos. In cultured cells, M-TKs generated reactive oxygen species that triggered apoptosis via the mitochondrial pathway without directly disrupting the cell-membrane or damaging nuclear DNA. The cytotoxicity and wide scope for structural variation of M-TKs indicate the potential of synthetic metal-organic knots as a new field of chemical space for pharmaceutical design and development.
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[This corrects the article DOI: 10.1039/C8SC02842G.].
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Covalent organic nanosheets (CONs) have attracted much attention because of their excellent physical, chemical, electronic, and optical properties. Although covalent organic nanosheets have widely been used in many applications, there are only a few CONs that have been tested for bio-medical applications. Nanometer sized triazine-based nanosheets were obtained by exfoliating their bulk counterparts in water. The obtained nanosheets were dispersible and stable in water with enhanced photoluminescence properties compared to the bulk material. The nanosheets were biocompatible and non-toxic and showed ability to stain HeLa cell nuclei without additional assistance of an external targeting agent.
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Topological transformation of a zinc-templated trefoil knot, Zn-TK, into a zinc-templated [2]catenane, Zn-[2]C, was studied. The net reaction 2 Zn-TKâ3 Zn-[2]C was accomplished in 89% yield by heating a solution of Zn-TK in D2O. Kinetic investigation by 1H NMR spectroscopy and high resolution mass spectrometry revealed that the mechanism is complex, involving a large pool of intermediates that form after imine bond cleavage. Bromide ions, which can occupy the central cavity of Zn-TK, inhibited the reaction. Two similar transformations were also studied, one of a cadmium-containing trefoil knot, Cd-TK, into a cadmium-containing catenane, Cd-[2]C, and the other of Cd-TK into Zn-[2]C. The latter transformation could be achieved in one step at high temperature or in two steps via transmetallation to form Zn-TK at room temperature followed by topological conversion of Zn-TK to Zn-[2]C at high temperature.