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Coordination polymers, including metal–organic frameworks, are a diverse class of materials with myriad properties and potential applications. However, a number of drawbacks have hindered the scaling up of such materials towards commercial applications. These include health and safety risks, environmental hazards, poor cost efficiency and sustainability shortfalls. In contrast to the systematic progress of organic green chemistry, which has contributed to improvements in the sustainability of chemical processing, the development of green chemistry in the context of coordination polymers has been fragmented and sporadic. This review describes advances in the use of green components: benign sustainable ligands and non-hazardous earth abundant metals. Additionally, solvent considerations, synthesis strategies for improved sustainability and the performance of coordination polymers relative to alternative competing materials are discussed. [ABSTRACT FROM AUTHOR]

3D foam scaffolds were produced in a “bottom-up” approach from lyophilised cationic cellulose nanofibril (CCNF) dispersions and emulsions (CCNF degree of substitution 23.0 ± 0.9%), using a directional freezing/lyophilisation approach, producing internal architectures ranging from aligned smooth walled micro channels, mimicking vascularised tissue, to pumice-like wall textures, reminiscent of porous bone. The open, highly porous architecture of these biomimetic scaffolds included mesopores within the walls of the channels. A combination of SEM and NMR cryoporometry and relaxometry was used to determine the porosity at different length scales: CCNF foams with aligned channels had an average macropore (channel) size of 35 ± 9 μm and a mesopore (wall) diameter of 26 ± 2 nm, while CCNF foams produced from directional freezing and lyophilisation of Pickering emulsions had mesoporous walls (5 ± 3 μm) in addition to channels (54 ± 20 μm). Glyoxal crosslinking both enhanced robustness and stiffness, giving Young's moduli of 0.45 to 50.75 MPa for CCNF foams with degrees of crosslinking from 0 to 3.04 mol%. Porosity and channels are critical scaffold design elements for transport of nutrients and waste products, as well as O2/CO2 exchange. The viability of MG-63 cells was enhanced on crosslinked, mechanically stiff scaffolds, indicating that these exquisitely structured, yet robust, foams could provide biomaterial scaffolds suitable for industrial applications requiring 3D cell culturing. [ABSTRACT FROM AUTHOR]

The structure of dispersions of TEMPO-oxidised cellulose nanofibrils (OCNF), at various concentrations, in water and in NaCl aqueous solutions, was probed using small angle X-ray scattering (SAXS). OCNF are modelled as rod-like particles with an elliptical cross-section of 10 nm and a length greater than 100 nm. As OCNF concentration increases above 1.5 wt%, repulsive interactions between fibrils are evidenced, modelled by the interaction parameter νRPA ＞ 0. This corresponds to gel-like behaviour, where G′ ＞ G′′ and the storage modulus, G′, shows weak frequency dependence. Hydrogels can also be formed at OCNF concentration of 1 wt% in 0.1 M NaCl(aq). SAXS patterns shows an increase of the intensity at low angle that is modelled by attractive interactions (νRPA ＜ 0) between OCNF, arising from the screening of the surface charge of the fibrils. Results are supported by ζ potential and cryo-TEM measurements. [ABSTRACT FROM AUTHOR]

Cellulose films as well as chitosan-modified cellulose films of approximately 5 μm thickness, reconstituted from ionic liquid media onto a poly(ethylene-terephthalate) (PET, 6 μm thickness) film with a 5, 10, 20, or 40 μm diameter laser-drilled microhole, show significant current rectification in aqueous NaCl. Reconstituted α-cellulose films provide “cationic diodes” (due to predominant cation conductivity) whereas chitosan-doped cellulose shows “anionic diode” effects (due to predominant anion conductivity). The current rectification, or “ionic diode” behaviour, is investigated as a function of NaCl concentration, pH, microhole diameter, and molecular weight of the chitosan dopant. Future applications are envisaged exploiting the surface charge induced switching of diode currents for signal amplification in sensing. [ABSTRACT FROM AUTHOR]

Polysaccharides, such as cellulose, are often processed by dissolution in solvent mixtures, e.g. an ionic liquid (IL) combined with a dipolar aprotic co-solvent (CS) that the polymer does not dissolve in. A multi-walker, discrete-time, discrete-space 1-dimensional random walk can be applied to model solvation of a polymer in a multi-component solvent mixture. The number of IL pairs in a solvent mixture and the number of solvent shells formable, x, is associated with n, the model time-step, and N, the number of random walkers. The mean number of distinct sites visited is proportional to the amount of polymer soluble in a solution. By also fitting a polynomial regression model to the data, we can associate the random walk terms with chemical interactions between components and probe where the system deviates from a 1-D random walk. The ‘frustration’ between solvents shells is given as ln x in the random walk model and as a negative IL:IL interaction term in the regression model. This frustration appears in regime II of the random walk model (high volume fractions of IL) where walkers interfere with each other, and the system tends to its limiting behaviour. In the low concentration regime, (regime I) the solvent shells do not interact, and the system depends only on IL and CS terms. In both models (and both regimes), the system is almost entirely controlled by the volume available to solvation shells, and thus is a counting/space-filling problem, where the molar volume of the CS is important. Small deviations are observed when there is an IL–CS interaction. The use of two models, built on separate approaches, confirm these findings, demonstrating that this is a real effect and offering a route to identifying such systems. Specifically, the majority of CSs – such as dimethylformide – follow the random walk model, whilst 1-methylimidazole, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone and tetramethylurea offer a CS-mediated improvement and propylene carbonate results in a CS-mediated hindrance. It is shown here that systems, which are very complex at a molecular level, may, nonetheless, be effectively modelled as a simple random walk in phase-space. The 1-D random walk model allows prediction of the ability of solvent mixtures to dissolve cellulose based on only two dissolution measurements (one in neat IL) and molar volume. [ABSTRACT FROM AUTHOR]

The article offers information on life cycles of surfactants and plastics.

Bi-phasic oxidations using hydrogen peroxide oxidant and a tungsten-based catalyst (e.g. Na2WO4) can proceed quickly and effectively without the need for organic solvents or added phase transfer agents in emulsified systems. Providing sufficient contact area between phases easily overcomes the physical limitations associated with the phase transfer of species, facilitating its scale-up, recyclability of the catalyst and easing product separation. Using the epoxidation of sunflower seed oil as a model reaction, we have also shown how the chemical and safety limitations associated with the parallel decomposition of hydrogen peroxide by Na2WO4 can be suppressed by the use of readily available water soluble organic carboxylic acids and careful consideration of the catalyst to acid ratio. The combination of chemical and engineering solutions with a near 100% hydrogen peroxide use, makes, for the first time, this green oxidation pathway attractive for large-scale industrial applications. [ABSTRACT FROM AUTHOR]

N-Oxyl mediated oxidations are becoming widely applied to the selective oxidation of a range of substrates bearing primary alcohol groups, including renewable biopolymers such as cellulose, but screening of mediators and oxidation conditions can be a laborious process, potentially limiting discovery of new mediators and/or optimised conditions for reaction. We describe a simple method for rapid voltammetric screening of mediators and reaction conditions that requires only small quantities of mediator (so is suitable for screening new synthetic or natural mediators) and yet yields information about relative efficiency of mediator, optimum pH, and preferred buffer identity. Such methodology may be used to speed mediator screening and selection of optimal and greenest reaction conditions prior to preparation, or isolation, of large quantities of mediators. [ABSTRACT FROM AUTHOR]

Partially C(6) oxidised, dispersed cellulose nanofibres form shear thinning gels in the presence of moderate amounts of simple salts or surfactants providing a novel method to structure aqueous formulations, which may be of use in a substantial number of applications where it is desirable to enhance the viscosity of formulated materials using components from a renewable, sustainable source. [ABSTRACT FROM AUTHOR]

The copper(II) coordination compound of an N-functionalised derivative of tris(2-aminoethyl)amine forms a cavity that is an excellent fluoride ion host, generating a Cu-F entity with a very short distance (182 pm) and characterised by a fluoride ion devoid of any additional intermolecular interactions. [ABSTRACT FROM AUTHOR]

Cellulose foams, or sponges, are produced from solutions in ionic liquids by the aqueous acid mediated decomposition of 1-alkyl-3-methylimidazolium-2-carboxylates, where the alkyl group and acid may be selected such that the by-product is the ionic liquid solvent: a by-productless foaming. [ABSTRACT FROM AUTHOR]

Polysaccharides, such as cellulose, are often processed by dissolution in solvent mixtures, e.g. an ionic liquid (IL) combined with a dipolar aprotic co-solvent (CS) that the polymer does not dissolve in. A multi-walker, discrete-time, discrete-space 1-dimensional random walk can be applied to model solvation of a polymer in a multi-component solvent mixture. The number of IL pairs in a solvent mixture and the number of solvent shells formable, x, is associated with n, the model time-step, and N, the number of random walkers. The mean number of distinct sites visited is proportional to the amount of polymer soluble in a solution. By also fitting a polynomial regression model to the data, we can associate the random walk terms with chemical interactions between components and probe where the system deviates from a 1-D random walk. The 'frustration' between solvents shells is given as ln x in the random walk model and as a negative IL:IL interaction term in the regression model. This frustration appears in regime II of the random walk model (high volume fractions of IL) where walkers interfere with each other, and the system tends to its limiting behaviour. In the low concentration regime, (regime I) the solvent shells do not interact, and the system depends only on IL and CS terms. In both models (and both regimes), the system is almost entirely controlled by the volume available to solvation shells, and thus is a counting/space-filling problem, where the molar volume of the CS is important. Small deviations are observed when there is an IL-CS interaction. The use of two models, built on separate approaches, confirm these findings, demonstrating that this is a real effect and offering a route to identifying such systems. Specifically, the majority of CSs - such as dimethylformide - follow the random walk model, whilst 1-methylimidazole, dimethyl sulfoxide, 1,3-dimethyl-2-imidazolidinone and tetramethylurea offer a CS-mediated improvement and propylene carbonate results in a CS-mediated hindrance. It is shown here that systems, which are very complex at a molecular level, may, nonetheless, be effectively modelled as a simple random walk in phase-space. The 1-D random walk model allows prediction of the ability of solvent mixtures to dissolve cellulose based on only two dissolution measurements (one in neat IL) and molar volume.

The copper(ii) coordination compound of an N-functionalised derivative of tris(2-aminoethyl)amine forms a cavity that is an excellent fluoride ion host, generating a Cu-F entity with a very short distance (182 pm) and characterised by a fluoride ion devoid of any additional intermolecular interactions.

Ionic liquids comprised of tetradecyltrihexyl- and tetrabutyl-phosphonium cations paired with chloride or sulfonyl amide anions exhibit properties that reflect strong ion association, including comparatively low viscosity as well as a degree of volatility, and hence exemplify an interesting intermediate state between true ionic and true molecular liquids.

The stoichiometric treatment of 2,6-dibenzylphenol (HOdbp) or 2,2"-dimethoxy-2,6-dibenzylphenol (HOdbpOMe) with n-butyllithium or sodium bis(trimethylsilyl)amide (the latter as a solution in THF) in Et2O or DME affords the dimeric alkali metal phenolates [{M(Odbp)(L)}2] (M = Li; L = Et2O (1), L = DME (2), M = Na; L = Et2O (5), L = DME (6)), [{Li(OdbpOMe)}2] (3) and [{M(OdbpOMe)(L)}2] (M = Li; L = DME (4), M = Na; L = THF (7), L = DME (8)). Complexes 3 and 7 exhibit -OdbpOMe methoxy coordination and all four sodium complexes (5-8) display pi-aryl contacts from one phenolate radial arm to each sodium centre. The attempted synthesis of {Na(odbp)}n by direct sodiation of HOdbp yields a small quantity of the 2-benzylphenolate [{Na(Ombp)(DME)}4] (9) (-Ombp = -OC6H4-2-CH2Ph), providing a rare example of benzyl C-C bond scission.

A member of a new class of novel macrocycles possessing both polyether and phenolic functionalities, forms dimers in both the solid-state and in solution when exposed to chloroform, dichloromethane or toluene, but does not self-associate in the presence of dimethyl sulfoxide.