Modelling adsorption in fluorinated TKL MOFs

<p>Ligand functionalisation resulting in unprecedented enhanced adsorption in a series of structurally similar, fluorinated metal-organic frameworks is studied using molecular computations and simulations. Strikingly anomalous experimental trends in the adsorption characteristics of the TKL FMOFs are investigated and understood here using classical and quantum chemical methods. Almost identical adsorption sites and energies for all the MOFs considered herein were observed. However, experimental isosteric heats and uptake amounts between these solids have been reported to be significantly different. Therefore, <i>ab initio</i> molecular dynamics simulations are performed to account for the drastic effects that flexible linkers can have on gas adsorption energetics, something that low-temperature crystallographic measurements cannot completely capture.</p

Structural Investigations on Lithium-Doped Protic and Aprotic Ionic Liquids

Solutions of lithium bis­(trifluoromethanesulfonyl)­imide (LiNTf₂), in four different [NTf₂]⁻-based ionic liquids, are extensively investigated as potential electrolytes for lithium-ion batteries. Solvation of the [Li]⁺ ions in the ionic liquids and its impact on their physicochemical properties are studied herein with the aid of molecular dynamics simulations. The cationic components of the investigated liquids were systematically varied so as to individually evaluate effects of specific structural changes; increase in ring size, the addition of an alkyl chain and absence of an acidic proton, on the solvation and mobility of the [Li]⁺ cations. The studied cations also allow for a direct comparison between solutions of [Li]⁺ salt in protic and aprotic ionic liquids. Emphasis is laid on elucidating the interactions between the [Li]⁺ and [NTf₂]⁻ ions revealing slightly higher coordination numbers for the aprotic solvent, benchmarked against experimental measurements. The study suggests that the ionic liquids largely retain their structure upon salt addition, with interactions within the liquids only slightly perturbed. The rattling motion of the [Li]⁺ cations within cages formed by the surrounding [NTf₂]⁻ anions is examined by the analysis of [Li]⁺ autocorrelation functions. Overall, the solvation mechanism of [Li]⁺ salt, within the hydrogen-bonded network of the ionic liquids, is detailed from classical and <i>ab initio</i> molecular dynamics simulations

Insights into Bulk Electrolyte Effects on the Operative Voltage of Electrochemical Double-Layer Capacitors

Electrochemical double-layer capacitors (EDLCs) are robust, high-power, and fast-charging energy storage devices. Rational design of novel electrolyte materials could further improve the performance of EDLCs. Computational methods offer immense scope in aiding the development of such materials. Trends in experimentally observed operative voltages nevertheless remain difficult to predict and understand. We discuss here the intriguing case of adiponitrile (ADN) versus 2-methyl-glutaronitrile (2MGN) based electrolytes, which result in very different operative voltages in EDLCs despite structural similarity. As a preliminary step, bulk electrolyte effects on electrochemical stability are investigated by <i>ab initio</i> molecular dynamics (AIMD) and static, cluster-based quantum chemistry calculations