No abstract

Dynamic and flexible metal–organic frameworks (MOFs) that respond to external stimuli, such as stress, light, heat, and the presence of guest molecules, hold promise for applications in chemical sensing, drug delivery, gas separations, and catalysis.

Capture of CO2 from flue gas is considered to be a feasible approach to mitigate the effects of anthropogenic emission of CO2. Herein we report that an isostructural family of metal organic materials (MOMs) of general formula [M(linker)2(pillar)], linker = pyrazine, pillar = hexaflourosilicate and M = Zn, Cu, Ni and Co exhibits highly selective removal of CO2 from dry and wet simulated flue gas. Two members of the family, M = Ni and Co, SIFSIX-3-Ni and SIFSIX-3-Co, respectively, are reported for the first time and compared with the previously reported Zn and Cu analogs.

The demand for Xe/Kr separation continues to grow due to the industrial significance of high-purity Xe gas. Current separation processes rely on energy intensive cryogenic distillation. Therefore, less energy intensive alternatives, such as physisorptive separation, using porous materials, are required. Herein we show that an underexplored class of porous materials called hybrid ultra-microporous materials (HUMs) affords new benchmark selectivity for Xe separation from Xe/Kr mixtures. The isostructural materials, CROFOUR-1-Ni and CROFOUR-2-Ni, are coordination networks that have coordinatively saturated metal centers and two distinct types of micropores, one of which is lined by CrO4 (2-) (CROFOUR) anions and the other is decorated by the functionalized organic linker. These nets offer unprecedented selectivity towards Xe. Modelling indicates that the selectivity of these nets is tailored by synergy between the pore size and the strong electrostatics afforded by the CrO4 (2-) anions.

We report the synthesis, structure, and sorption properties of a family of eight diamondoid (dia) metal-organic materials (MOMs) that are sustained by Co(II) or Zn(II) cations linked by one of three rigid ligands: 4-(2-(4-pyridyl)ethenyl)benzoate (1), 4-(pyridin-4-yl)benzoate (2), and 4-(pyridin-4-yl)acrylate (3). Pore size control in this family of dia nets was exerted by two approaches: changing the length of the linker ligand from 1 to 3, and using solvent as a template to control the level of interpenetration in nets based upon 1 and 3. The resulting MOMs, dia-8i-1, dia-5i-3, dia-7i-1-Zn, dia-7i-1-Co, dia-4i-3-a, dia-4i-3-b, dia-4i-2, and dia-4i-1, exhibit 1D channels with pore limiting diameters (PLDs) of 1.64, 2.90, 5.06, 5.28, 8.57, 8.83, 11.86, and 18.25 Å, respectively. We selected dia nets for this study for the following reasons: their 1D channels facilitate study of the impact of pore size on gas sorption parameters in situations where pore chemistry is similar (pyridyl benzoate-type linkers) or identical (in the case of polymorphs), and their saturated metal centers eliminate open metal sites from dominating sorbent-solvate interactions and possibly masking the effect of pore size. Our data reveal that smaller pore sizes offer stronger interactions, as determined by the isosteric heat of adsorption (Qst) and the steepness of the adsorption isotherm in the low-pressure region. The porous MOM with the smallest PLD suitable for physisorption, dia-7i-1-Co, was thereby found to exhibit the highest Qst values for CO2 and CH4. Indeed, dia-7i-1-Co exhibits a Qst for CH4 of 26.7 kJ/mol, which was validated through grand canonical Monte Carlo simulation studies of CH4 adsorption. This Qst value is considerably higher than those found in covalent organic frameworks and other MOMs with unsaturated metal centers. These results therefore further validate the critical role that PLD plays in gas adsorption by porous MOMs.

The sorptive uptake properties are reported for chitosan and cross-linked chitosan–glutaraldehyde (CG) polymers with single component and mixtures of carboxylic acids (surrogates;Si, i = 1–4).

A novel 4(8).6(7) topology metal-organic material (MOM) platform of formula [M(bpe)(2)(M'O(4))] (M = Co or Ni; bpe = 1,2-bis(4-pyridyl)ethene; M' = Mo or Cr) has been synthesized and evaluated in the context of gas sorption. These MOMs have been assigned RCSR code mmo and are uninodal 6-connected nets. [Ni(bpe)(2)(MoO(4))], MOOFOUR-1-Ni, and its chromate analogue, CROFOUR-1-Ni, exhibit high CO(2) affinity and selectivity, especially at low loading. This behavior can be attributed to exceptionally high isosteric heats of adsorption (Q(st)) of CO(2) in MOOFOUR-1-Ni and CROFOUR-1-Ni of ∼56 and ∼50 kJ/mol, respectively, at zero loading. These results were validated by molecular simulations which indicate that the electrostatics of these inorganic anions affords attractions toward CO(2) that are comparable to those of unsaturated metal centers.

Optimization of medium composition for the improvement of heterotrophic cultivation of green microalgae, Tetraselmis suecica, was performed using response surface methodology (RSM). Heterotrophic cultivation of T. suecica was conducted in total darkness using Walne medium formulated with natural sea water. Initially, the effect of two types of carbon source (glucose and sodium acetate) and various types of nitrogen source (peptone, yeast extract, meat extract, malt extract, urea, sodium nitrate and ammonium nitrate) on growth of T. suecica was studied. The concentration of medium component that was found to significantly influence the heterotrophic growth of T. suecica (glucose, peptone, yeast extract and meat extract) was further optimized using RSM. The medium that consists of 5.78 g/L glucose, 9 g/L peptone, 4.48 g/L yeast extract and 3.01 g/L meat extract was found optimal for heterotrophic cultivation of T. suecica. The final cell concentration (28.88 g/L) obtained in heterotrophic cultivation using this optimized medium was about 3 and 2 times higher than obtained in photoautotrophic culture (8.40 g/L) and non-optimized medium for heterotrophic cultivation (13.81 g/L), respectively. In addition, the cell yield based on glucose consumed (9.31 g cell/g glucose) was increased by about 3 times as compared to non-optimized medium (3.61 g cell/g glucose).