1,358 research outputs found

    Continuous flow synthesis of hypercrosslinked polymers (HCPs) and its environmental impact evaluation

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    Hypercrosslinked polymers(HCPs) are a class of microporous adsorbents with a wide range of applications, including dye adsorption, and gas storage. Traditionally, HCPs are synthesised through Friedel-Crafts alkylation, which involves a time-consuming synthesis process in batch reactors, posing challenges for scaling up production to meet global demand. The prolong reaction duration issue could be eliminated by means of a new synthetic method to substitute batch reactors. The ultimate aim of this study is to intensify the HCP synthesis process by transitioning from batch reactors to continuous reactors. This shift intents to enhance productivity while maintaining a high specific surface area, crucial for superior adsorption capacity. Additionally, this study aspired to reduce the environmental impact associated with this new method for HCP synthesis. To achieve these objectives, a continuous flow system had been adopted as a replacement for the conventional batch method in HCP synthesis. Three types of HCPs were successfully synthesised using well-established strategies (internally crosslinked, post-crosslinked, and externally crosslinked) in the continuous flow system, showcasing its versatility. The productivity, measured as space-time-yield (STY), of continuous flow synthesis showed an enhancement ranging from 32 ÔÇô 117-fold when compared to batch synthesis. These improvements were attributed to reducing reaction duration during flow synthesis, from 1440 minutes (24 hours) to 5 ÔÇô 15 minutes. The specific surface areas of flow-synthesised HCPs were, on average, lower than the batch-synthesised HCPs by 1.5 ÔÇô 10 %. This meant that when compared to batch-synthesised HCPs, more quantities of flow-synthesised HCPs were needed for dye adsorption and CO2 capture. However, despite this requirement for larger quantities, the environmental assessment of continuous flow synthesis indicated a reduction in negative environmental impacts across most environmental impact indicators. This suggest an improvement in the environmental sustainability of continuous flow HCP synthesis compared to batch synthesis. Furthermore, this study also explored an alternative synthesis method using twin screw extraction (TSE) with deep eutectic solvents (DES), a benign solvent replacement for halogenated solvents, during HCP synthesis. Although this approach offers promising potential as the replacement of continuous flow synthesis using conventional halogenated solvents, further investigations are warranted for its optimisation. In conclusion, this thesis advocates for the adoption of continuous flow synthesis of HCPs, underlining its potential for productivity enhancement and reduced environmental impacts. This study lays the foundation for the potential industrial-scale implementation of continuous flow synthesis, bridging the gap between HCP supply and demand while contributing to lower environmental impacts in the production process

    Studies on Loading Salicylic Acid in Xerogel Films of Crosslinked Hyaluronic Acid.

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    During the last decades, salicylic acid (SA) and hyaluronic acid (HA) have been studiedfor a wide range of cosmetic and pharmaceutical applications. The current study investigated thedrug loading potential of SA in HA-based crosslinked hydrogel films using a post-loading (osmosis)method of the unmedicated xerogels from saturated aqueous solutions of salicylic acid over a rangeof pH values. The films were characterized with Fourier-transform infra-red spectroscopy (FT-IR) andultraviolet-visible (UV-Vis) spectrophotometry in order to elucidate the drug loading profile and thefilmsÔÇÖ integrity during the loading process. Additional studies on their weight loss (%), gel fraction(%), thickness increase (%) and swelling (%) were performed. Overall, the studies showed significantfilm disintegration at highly acidic and basic solutions. No drug loading occurred at neutral andbasic pH, possibly due to the anionic repulsion between SA and HA, whereas at, pH 2.1, the drugloading was promising and could be detected via UV-Vis analysis of the medicated solutions, withthe SA concentration in the xerogel films at 28% w/w

    Dinamika samoudru┼żenih monoslojeva molekularnih strojeva na me─Ĺupovr┼íini voda/zrak

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    We present a computational study of self-assembled monolayers (SAMs) of several functional molecules which share a triptycene core and differ in the number of anchoring groups and functional mounts (photoswitches or light-driven motors). Structural properties of different SAMs on the water-air interface are explored by nanoscale molecular dynamics carried out in the tight-binding DFT formalism, as well as by static meta-GGA DFT calculations. Both approaches give similar results, revealing that tilting and bending in SAMs is significant in all investigated systems. Molecular dynamics shows that SAMs tilt collectively, although the motion of individual machines is not strongly correlated. Functional heads, triptycenes and anchoring groups are found to strongly affect SAM properties, and a structure bearing two triptycene units and three anchoring groups is identified as the most promising future synthetic target. Finally, the computational results are validated by comparing them with previously performed experiments (anisotropic spectroscopy and ellipsometry).U ovom radu ra─Źunalnim su metodama istra┼żeni samoudru┼żeni monoslojevi (SAM) niza funkcionalnih molekula koje se razlikuju po funkcionalnoj jedinici (sklopka ili svjetlom upogonjeni motor) i broju veznih skupina, a dijele tripticensku jezgru. Strukturna svojstva razli─Źitih SAM-ova na me─Ĺupovr┼íini voda-zrak istra┼żena su nanosekundnom molekulskom dinamikom provedenom u formalizmu DFT modela ─Źvrste veze, te meta-GGA DFT stati─Źkim izra─Źunima. Oba pristupa daju sli─Źne rezultate i otkrivaju da su, u svim prou─Źavanim sustavima, molekule zna─Źajno nagnute i savinute. Rezultati molekulske dinamike pokazuju da je nagibanje SAM-ova kolektivan proces, iako gibanje individualnih strojeva nije korelirano. Tako─Ĺer, potvr─Ĺeno je da funkcionalne glave, tripticeni i vezne skupine zna─Źajno utje─Źu na svojstva monoslojeva, te je kao glavni kandidat za sintezu novih funkcionalnih materijala identificiran molekulski sustav s dvije tripticenske jedinice i tri vezne skupine. Usporedbom s prethodno provedenim eksperimentima (anizotropnom spektroskopijom i elipsometrijom) potvr─Ĺeni su ra─Źunalni rezultati

    Synthesizing Hypercrosslinked Polymers with Deep Eutectic Solvents to Enhance CO2/N2 Selectivity

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    Hypercrosslinked polymers (HCPs) are widely used in ion exchange, water purification, and gas separation. However, HCP synthesis typically requires hazardous halogenated solvents e.g., dichloroethane, dichloromethane and chloroform which are toxic to human health and environment. Herein we hypothesize that the use of halogenated solvents in HCP synthesis can be overcome with deep eutectic solvents (DES) comprising metal halides ÔÇô FeCl3, ZnCl2 that can act as both the solvent hydrogen bond donor and catalyst forpolymer crosslinking via Friedel Crafts alkylation. We validated our hypothesis by synthesizing HCPs in DESs via internal and external crosslinking strategies. [ChCl][ZnCl2]2 and [ChCl][FeCl3]2 was more suitable for internal and external hypercrosslinking, respectively. The specific surface areas of HCPs synthesized in DES were 20 ÔÇô 60 % lower than those from halogenated solvents, but their CO2/N2 selectivities were up to 453 % higher (CO2/N2 selectivity of poly-╬▒,╬▒ÔÇÖ-dichloro-p-xylene synthesized in [ChCl][ZnCl2]2 via internal crosslinking reached a value of 105). This was attributed to the narrower pore size distributions of HCPs synthesized in DESs

    Synthesis of 12-Connected Three-Dimensional Covalent Organic Framework with lnj Topology

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    The structural exploration of three-dimensional covalent organic frameworks (3D COFs) is of great significance to the development of COF materials. Different from structurally diverse MOFs, which have a variety of connectivity (3ÔÇô24), now the valency of 3D COFs is limited to only 4, 6, and 8. Therefore, the exploration of organic building blocks with higher connectivity is a necessary path to broaden the scope of 3D COF structures. Herein, for the first time, we have designed and synthesized a 12-connected triptycene-based precursor (triptycene-12-CHO) with 12 symmetrical distributions of aldehyde groups, which is also the highest valency reported until now. Based on this unique 12-connected structure, we have successfully prepared a novel 3D COF with lnj topology (termed 3D-lnj-COF). The as-synthesized 3D COF exhibits honeycomb main pores and permanent porosity with a BrunauerÔÇôEmmettÔÇôTeller surface area of 1159.6 m2 gÔÇô1. This work not only provides a strategy for synthesizing precursors with a high connectivity but also provides inspiration for enriching the variety of 3D COFs

    Dinamika samoudru┼żenih monoslojeva molekularnih strojeva na me─Ĺupovr┼íini voda/zrak

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    We present a computational study of self-assembled monolayers (SAMs) of several functional molecules which share a triptycene core and differ in the number of anchoring groups and functional mounts (photoswitches or light-driven motors). Structural properties of different SAMs on the water-air interface are explored by nanoscale molecular dynamics carried out in the tight-binding DFT formalism, as well as by static meta-GGA DFT calculations. Both approaches give similar results, revealing that tilting and bending in SAMs is significant in all investigated systems. Molecular dynamics shows that SAMs tilt collectively, although the motion of individual machines is not strongly correlated. Functional heads, triptycenes and anchoring groups are found to strongly affect SAM properties, and a structure bearing two triptycene units and three anchoring groups is identified as the most promising future synthetic target. Finally, the computational results are validated by comparing them with previously performed experiments (anisotropic spectroscopy and ellipsometry).U ovom radu ra─Źunalnim su metodama istra┼żeni samoudru┼żeni monoslojevi (SAM) niza funkcionalnih molekula koje se razlikuju po funkcionalnoj jedinici (sklopka ili svjetlom upogonjeni motor) i broju veznih skupina, a dijele tripticensku jezgru. Strukturna svojstva razli─Źitih SAM-ova na me─Ĺupovr┼íini voda-zrak istra┼żena su nanosekundnom molekulskom dinamikom provedenom u formalizmu DFT modela ─Źvrste veze, te meta-GGA DFT stati─Źkim izra─Źunima. Oba pristupa daju sli─Źne rezultate i otkrivaju da su, u svim prou─Źavanim sustavima, molekule zna─Źajno nagnute i savinute. Rezultati molekulske dinamike pokazuju da je nagibanje SAM-ova kolektivan proces, iako gibanje individualnih strojeva nije korelirano. Tako─Ĺer, potvr─Ĺeno je da funkcionalne glave, tripticeni i vezne skupine zna─Źajno utje─Źu na svojstva monoslojeva, te je kao glavni kandidat za sintezu novih funkcionalnih materijala identificiran molekulski sustav s dvije tripticenske jedinice i tri vezne skupine. Usporedbom s prethodno provedenim eksperimentima (anizotropnom spektroskopijom i elipsometrijom) potvr─Ĺeni su ra─Źunalni rezultati

    Dinamika samoudru┼żenih monoslojeva molekularnih strojeva na me─Ĺupovr┼íini voda/zrak

    No full text
    We present a computational study of self-assembled monolayers (SAMs) of several functional molecules which share a triptycene core and differ in the number of anchoring groups and functional mounts (photoswitches or light-driven motors). Structural properties of different SAMs on the water-air interface are explored by nanoscale molecular dynamics carried out in the tight-binding DFT formalism, as well as by static meta-GGA DFT calculations. Both approaches give similar results, revealing that tilting and bending in SAMs is significant in all investigated systems. Molecular dynamics shows that SAMs tilt collectively, although the motion of individual machines is not strongly correlated. Functional heads, triptycenes and anchoring groups are found to strongly affect SAM properties, and a structure bearing two triptycene units and three anchoring groups is identified as the most promising future synthetic target. Finally, the computational results are validated by comparing them with previously performed experiments (anisotropic spectroscopy and ellipsometry).U ovom radu ra─Źunalnim su metodama istra┼żeni samoudru┼żeni monoslojevi (SAM) niza funkcionalnih molekula koje se razlikuju po funkcionalnoj jedinici (sklopka ili svjetlom upogonjeni motor) i broju veznih skupina, a dijele tripticensku jezgru. Strukturna svojstva razli─Źitih SAM-ova na me─Ĺupovr┼íini voda-zrak istra┼żena su nanosekundnom molekulskom dinamikom provedenom u formalizmu DFT modela ─Źvrste veze, te meta-GGA DFT stati─Źkim izra─Źunima. Oba pristupa daju sli─Źne rezultate i otkrivaju da su, u svim prou─Źavanim sustavima, molekule zna─Źajno nagnute i savinute. Rezultati molekulske dinamike pokazuju da je nagibanje SAM-ova kolektivan proces, iako gibanje individualnih strojeva nije korelirano. Tako─Ĺer, potvr─Ĺeno je da funkcionalne glave, tripticeni i vezne skupine zna─Źajno utje─Źu na svojstva monoslojeva, te je kao glavni kandidat za sintezu novih funkcionalnih materijala identificiran molekulski sustav s dvije tripticenske jedinice i tri vezne skupine. Usporedbom s prethodno provedenim eksperimentima (anizotropnom spektroskopijom i elipsometrijom) potvr─Ĺeni su ra─Źunalni rezultati

    Crystal Structures of Metal Complexes

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    This reprint contains 11 papers published in a Special Issue of Molecules entitled "Crystal Structures of Metal Complexes". I will be very happy if readers will be interested in the crystal structures of metal complexes

    Hydrogen-bonding receptors for anion recovery in a capacitive deionisation system

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    Receptors are ubiquitous throughout nature and are found heavily within biological systems. This has led to synthetic supramolecular chemists to modify or develop analogous mimics of these receptors with high affinity and specificity for a range of target compounds, for potential commercial use. One group of particular interest are receptors that function through the formation of hydrogen bonds to the guest species. This class of receptor has been shown to have a range of different structural geometries and binding motifs, that allow for the sequestration of a number of different species. In the context of this work, anionic hydrogen-bonding receptors, specifically for ÔÇśphosphateÔÇÖ- in most cases dihydrogenphosphate- and bicarbonate are of interest. Phosphate is an integral part of the DNA backbone, however a organophosphorus containing compounds also comprise a large group of chemical weapons which can have a devasting impact on the bodies ability to function. Chemical weapon compounds, such as sarin and Novichok, are based on the functionalisation of a central phosphate core which can be biotransformed into a highly potent active species within the body. Phosphate is also an essential component of plant fertilizers and is used on a huge scale in order to maintain global food security. However, phosphate loss as a consequence of agricultural run-off leads to reduced availability of essential minerals as well as large scale eutrophication. One such method that could be utilised for the recovery of phosphate is electrochemical capacitive deionisation. The principle and idea of capacitive deionisation has been around since the late 1960ÔÇÖs to early 1970ÔÇÖs and has been shown to be a suitable method for the desalination of low-to-medium salinity input streams. The purpose of the work within this thesis was to modify and synthesise receptors that could be covalently attached to porous carbon electrodes and impart selectivity to a capacitive deionisation system. In Chapter 1, the importance of ÔÇśphosphateÔÇÖ, biologically and commercially is addressed before an in depth look at some of the phosphate specific hydrogen bonding receptors that have been reported in the literature. The design of a successful hydrogen bonding receptor relies on the correct orientation of the binding motifs and the range of structural scaffolds have been shown to be useable. Following this, the electrochemical principles of capacitive deionisation and its suitability for the recovery of phosphate are detailed, including some examples of capacitive deionisation set-ups and the overall processes involved. Chapter 2 details the theory of the techniques used throughout this thesis, which include, but not limited to, 1H and 13C NMR for the structural elucidation of the synthesised receptors and cyclic voltammetry which was used for the attachment of organic groups to an electrode. The historical and theoretical background established in Chapters 1 and 2 will lead into the work undertaken in Chapters 3-5. Chapter 3 focusses on the first of three hydrogen bonding receptors synthesised. Building upon previous work within the field, two neutral indole-based receptors were modified to include two different potential attachment points for the electrode- a carboxylic acid and an alkyne. Following the successful synthesis of the alkyne-based receptor, 1H NMR titrations were used to confirm the affinity of the new receptor for dihydrogenphosphate. Chapter 4 introduces the second anion of interest, bicarbonate. The underlying principles for hydrogen bonding are the same for bicarbonate, as in phosphate, however a different receptor was synthesised. The carbazole receptor synthesised contained free amine groups that were proposed to act as points of attachment to an already surface bound organic spacer group. 1H NMR titrations are once again used to determine the affinity of the receptor for the bicarbonate anion. Finally, Chapter 5 introduces the second of the dihydrogenphosphate-specific receptors, this time based on the amino acid leucine. UVVis titrations with a number of different anions were used to determine the affinity of the receptor. Within this chapter, methods for the attachment of organic groups are detailed including the electroreduction of 4-nitrobenzene diazonium and the direct oxidation of the alkyne

    Ultrasonic-assisted removal of cationic and anionic dyes residues from wastewater using functionalized triptycene-based polymers of intrinsic microporosity (PIMs)

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    In this work, a series of hypercrosslinked polymers of intrinsic microporosity (HCP-PIMs), namely nitro-triptycene (TRIP-NO2), amino-triptycene (TRIP-NH2), sulfonated-triptycene (TRIP-SO3H) and hydrocarbon-triptycene (TRIP-HC), are employed for the adsorption of organic dyes from wastewater. The materials show the efficient removal of cationic (malachite green, MG) and anionic (methyl orange, MO) dyes. The adsorption parameters herein investigated include the initial pH, the adsorbate concentration and the contact time, with the aim to elucidate their effect on the adsorption process. Furthermore, the adsorption kinetic and isotherms are studied, and the findings suggest the results fit well with pseudo-second-order kinetics and Langmuir model. The reported maximum adsorption capacity is competitive for all the tested polymers. More specifically, TRIP-SO3H and TRIP-HC exhibit adsorptions of ~ 303 and ~ 270 mg gÔłĺ1 for MG and MO, respectively. The selectivity toward cationic and anionic dyes is assessed by mixing the two dyes, and showing that TRIP-HC completely removes both species, whereas TRIP-NO2, TRIP-NH2 and TRIP-SO3H show an enhanced selectivity toward the cationic MG, compared to the anionic MO. The effect of the type of water is assessed by performing ultrasonic-assisted adsorption experiments, using TRIP-SO3H and TRIP-HC in the presence of either tap or seawater. The presence of competing ions and their concentrations is evaluated by ICP-MS. Our study shows that tap water does not have a detrimental effect on the adsorption of both polymers, whereas, in the presence of seawater, the performance of TRIP-HC toward MO proved to be more stable than MG with TRIP-SO3H, which is probably due to a larger concentration of competing ions. Comparison between ultrasonic-assisted and magnetic stirring adsorption demonstrates that the former exhibits a greater efficiency. This seems due to a more rapid mass transfer, driven by the formation of high velocity micro-jets, acoustic microstreaming and shock waves, at the polymer surface. Reusability studies show a good stability up to five adsorptionÔÇôdesorption cycles
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