Hydrogen fuel is attractive to power vehicles without emitting carbon, but onboard storage of sufficiently densified hydrogen at moderate pressure remains a significant challenge. Adsorption-based storage in porous crystals such as metal–organic frameworks and covalent organic frameworks is attractive to reduce the storage pressure. It is, however, unclear to what extent volumetric storage targets can be met under constraints of adsorbent design and choice of operating conditions. To help elucidate attainable values for volumetric storage metrics upon the potential introduction of strong hydrogen-binding sites, we “computationally synthesized” a library of porous crystals and performed 18 000+ grand canonical Monte Carlo simulations to calculate hydrogen loadings at multiple T, P conditions. The studied frameworks are based on 17 pore topologies and feature alchemical catecholate sites: sites whose interaction with hydrogen was artificially and systematically modified within the range of density functional theory-calculated hydrogen–catecholate binding energies found in the literature. Porous crystals with the tetrahedrally connected topologies dia and qtz tended to outperform other types of crystals for each “level” of hydrogen–alchemical site interaction strength. Among tested operating conditions, 100 bar/77 K ↔ 5 bar/160 K swing conditions produced the highest optimal deliverable capacity (62 g/L with a 10 kJ/mol heat of adsorption), which was 138% higher than that for the 100 bar ↔ 5 bar swing at ambient temperature (26 g/L with a 17 kJ/mol heat of adsorption). Porous crystals simultaneously featuring void fractions and volumetric surface areas in the 0.7–0.9 and 1300–1800 m2/cm3 ranges, respectively, were more susceptible to improvements in deliverable capacity for the 100 bar/77 K ↔ 5 bar/160 K swing by tuning their interactions with hydrogen. Select simulations were analyzed in more detail to obtain adsorption mechanism insights. Leveraging all of the generated data, we trained, for the first time, a single artificial neural network capable of predicting hydrogen loadings at multiple T, P conditions. Using this neural network, we estimated that, for the nonisothermal 77 K ↔ 160 K swing, reducing the storage pressure from 100 to 35 bar only reduces the attainable deliverable capacity to 59 g/L, which may be an acceptable trade-off due to safety and compression cost implications. As the neural network only uses simple descriptors as input, modelers and experimentalists alike could potentially use it to rapidly pre-assess the hydrogen storage capabilities of newly proposed crystal designs at various swing conditions.

New family of SO2F-functionalized ionic liquids.

We developed lipid-like ionic liquids, containing 2mercaptoimidazolium and 2-mercaptothiazolinium headgroups tethered to two long saturated alkyl chains, as carriers for in vitro delivery of plasmid HEK DNA into 293T cells. We employed a combination of modular design, synthesis, X-ray analysis, and computational modeling to rationalize the self-assembly and desired physicochemical and biological properties. The results suggest that thioamide-derived ionic liquids may serve as a modular platform for lipid-mediated gene delivery. This work represents a step toward understanding the structure−function relationships of these amphiphiles with long-range ordering and offering insight into design principles for synthetic vectors based on self-assembly behavior.

A fundamental challenge underlying the design principles of ionic liquids (ILs) entails a lack of understanding into how tailored properties arise from the molecular framework of the constituent ions. Herein, we present detailed analyses of novel functional ILs containing a triarylmethyl (trityl) motif. Combining an empirically driven molecular design, thermophysical analysis, X-ray crystallography, and computational modeling, we achieved an in-depth understanding of structure–property relationships, establishing a coherent correlation with distinct trends between the thermophysical properties and functional diversity of the compound library. We observe a coherent relationship between melting (T m) and glass transition (T g) temperatures and the location and type of chemical modification of the cation. Furthermore, there is an inverse correlation between the simulated dipole moment and the T m/T g of the salts. Specifically, chlorination of the ILs both reduces and reorients the dipole moment, a key property controlling intermolecular interactions, thus allowing for control over T m/T g values. The observed trends are particularly apparent when comparing the phase transitions and dipole moments, allowing for the development of predictive models. Ultimately, trends in structural features and characterized properties align with established studies in physicochemical relationships for ILs, underpinning the formation and stability of these new lipophilic, low-melting salts.

In this work, we investigated the effects of a single covalent link between hydrogen bond donor species on the behavior of deep eutectic solvents (DESs) and shed light on the resulting interactions at molecular scale that influence the overall physical nature of the DES system. We have compared sugar-based DES mixtures, 1:2 choline chloride/glucose [DES(g)] and 1:1 choline chloride/trehalose [DES(t)]. Trehalose is a disaccharide composed of two glucose units that are connected by an α-1,4-glycosidic bond, thus making it an ideal candidate for comparison with glucose containing DES(g). The differential scanning calorimetric analysis of these chemically close DES systems revealed significant difference in their phase transition behavior. The DES(g) exhibited a glass transition temperature of −58 °C and behaved like a fluid at higher temperatures, whereas DES(t) exhibited marginal phase change behavior at −11 °C and no change in the phase behavior at higher temperatures. The simulations revealed that the presence of the glycosidic bond between sugar units in DES(t) hindered free movement of sugar units in trehalose, thus reducing the number of interactions with choline chloride compared to free glucose molecules in DES(g). This was further confirmed using quantum theory of atoms in molecule analysis that involved determination of bond critical points (BCPs) using Laplacian of electron density. The analysis revealed a significantly higher number of BCPs between choline chloride and sugar in DES(g) compared to DES(t). The DES(g) exhibited a higher amount of charge transfer between the choline cation and sugar, and better interaction energy and enthalpy of formation compared to DES(t). This is a result of the ability of free glucose molecules to completely surround choline chloride in DES(g) and form a higher number of interactions. The entropy of formation for DES(t) was slightly higher than that for DES(g), which is a result of fewer interactions between trehalose and choline chloride. In summary, the presence of the glycosidic bond between the sugar units in trehalose limited their movement, thus resulting in fewer interactions with choline chloride. This limited movement in turn diminishes the ability of the hydrogen bond donor to disrupt the molecular packing within the lattice structure of the hydrogen bond acceptor (and vice versa), a crucial factor that lowers the melting point of DES mixtures. This inability to move due to the presence of the glycosidic bond in trehalose significantly influences the physical state of the DES(t) system, making it behave like a semi-solid material, whereas DES(g) behaves like a liquid material at room temperature.