Database for CO2 separation performances of MOFs based on computational materials screening

Metal-organic frameworks (MOFs) are potential adsorbents for CO2 capture. Because thousands of MOFs exist, computational studies become very useful in identifying the top performing materials for target applications in a time-effective manner. In this study, molecular simulations were performed to screen the MOF database to identify the best materials for CO2 separation from flue gas (CO2/N-2) and landfill gas (CO2/CH4) under realistic operating conditions. We validated the accuracy of our computational approach by comparing the simulation results for the CO2 uptakes, CO2/N-2 and CO2/CH4 selectivities of various types of MOFs with the available experimental data. Binary CO2/N-2 and CO2/CH4 mixture adsorption data were then calculated for the entire MOF database. These data were then used to predict selectivity, working capacity, regenerability, and separation potential of MOFs. The top performing MOF adsorbents that can separate CO2/N-2 and CO2/CH4 with high performance were identified. Molecular simulations for the adsorption of a ternary CO2/N-2/CH4 mixture were performed for these top materials to provide a more realistic performance assessment of MOF adsorbents. The structure-performance analysis showed that MOFs with Delta Q(st)(0) > 30 kJ/mol, 3.8 angstrom 1 g/cm(3) are the best candidates for selective separation of CO2 from flue gas and landfill gas. This information will be very useful to design novel MOFs exhibiting high CO2 separation potentials. Finally, an online, freely accessible database https://cosmoserc.ku.edu.tr was established, for the first time in the literature, which reports all of the computed adsorbent metrics of 3816 MOFs for CO2/N-2, CO2/CH4, and CO2/N-2/CH4 separations in addition to various structural properties of MOFs.European Research Counci

Generalizations from Molecular Simulation of Polyimide and Copolyimide sub-structures for the Robeson Diagram

Separation of many commercially important gas pairs using membranes is a growing application in the separation industry due to the advantages of membrane processes over traditional ones, such as lower capital cost and energy consumption, smaller footprint, ease of process integration, and lower maintenance costs. Substantial efforts have been expended in the search for superior polymeric materials with high performance separation, and mechanical and thermal resistance. Mainly, aromatic polymers like polyimides have emerged as a prominent membrane material in the gas separation area. Due to their rigid structure, these polymers show outstanding physical properties and high separation performance close to the trade-off relationships for many gas pairs. The thermal, mechanical and separation properties of polyimides strongly depend on their chemical structure, specifically in that a slight modification in their chemical structure may often result in a significant change in properties. Thus the development of structure-property relationships for polyimides, i.e., the ability to predict permeability and selectivity from polymeric structural units, provides for guidelines for designing optimum membrane candidates with desirable end-use properties.MOE (Min. of Education, S’pore

Solvation of a cellulose microfibril in imidazolium acetate ionic liquids: Effect of a cosolvent.

International audienceThe solvation and the onset of dissolution of a cellulose Iβ microcrystal in ionic liquid media are studied by molecular simulation. Ionic liquids can dissolve large amounts of cellulose, which can later be regenerated from solution, but their high viscosity is an inconvenience. Hydrogen bonding between the anion of the ionic liquid and cellulose is the main aspect determining dissolution. Here we try to elucidate the role of a molecular cosolvent, dimethyl sulfoxide (DMSO), which is an aprotic polar compound, in the system composed of cellulose and the ionic liquid 1-butyl-3-methylimidazolium acetate. We calculated quantities related to specific interactions (mainly hydrogen bonds), conformations, and the structure of local solvation environments, both for a solvated oligomer chain of cellulose and for a model microfibril composed of 36 chains in the Iβ crystal structure. We compare two solvent systems: the pure ionic liquid and a mixed solvent with an equimolar composition in ionic liquid and DMSO. All entities are represented by detailed all-atom, fully flexible force fields. The main conclusions are that DMSO behaves as an “innocent” cosolvent, lowering the viscosity and accelerating mass transport in the system, but without interacting specifically with cellulose or disrupting the interactions between cellulose with the anions of the ionic liquid. An understanding of solvation in mixed solvents composed of ionic liquids and molecular compounds can enable the design of high-performance media for the use of biomass materials

Solvation of a Cellulose Microfibril in Imidazolium Acetate Ionic Liquids: Effect of a Cosolvent

The solvation and the onset of dissolution of a cellulose I_β microcrystal in ionic liquid media are studied by molecular simulation. Ionic liquids can dissolve large amounts of cellulose, which can later be regenerated from solution, but their high viscosity is an inconvenience. Hydrogen bonding between the anion of the ionic liquid and cellulose is the main aspect determining dissolution. Here we try to elucidate the role of a molecular cosolvent, dimethyl sulfoxide (DMSO), which is an aprotic polar compound, in the system composed of cellulose and the ionic liquid 1-butyl-3-methylimidazolium acetate. We calculated quantities related to specific interactions (mainly hydrogen bonds), conformations, and the structure of local solvation environments, both for a solvated oligomer chain of cellulose and for a model microfibril composed of 36 chains in the I_β crystal structure. We compare two solvent systems: the pure ionic liquid and a mixed solvent with an equimolar composition in ionic liquid and DMSO. All entities are represented by detailed all-atom, fully flexible force fields. The main conclusions are that DMSO behaves as an “innocent” cosolvent, lowering the viscosity and accelerating mass transport in the system, but without interacting specifically with cellulose or disrupting the interactions between cellulose with the anions of the ionic liquid. An understanding of solvation in mixed solvents composed of ionic liquids and molecular compounds can enable the design of high-performance media for the use of biomass materials

Thermochromic Ionogel: A New Class of Stimuli Responsive Materials with Super Cyclic Stability for Solar Modulation

In this work, a new class of polyurethane based ionogels that can respond to external stimulus, e.g., temperature, has been synthesized. The ionogels are mechanically robust and undergo an LCST-type phase transition with no volume change upon heating accompanied by a switching of optical transmittance. The optical switching temperature is tunable within a wide range between subzero to over 100 °C. Molecular dynamic simulation aided molecular design and provided further mechanistic understanding. Apart from the LCST-type transition, these ionogels are absent of freezing point and volatility and demonstrated unprecedented superhigh optical cyclic stability even after 5000 heating–cooling cycles with no detectable liquid leaching. In addition, these ionogels are chemically compatible with a range of additives such as organic dyes and photothermal plasmonic conducting nanoparticles which endow multifunctionality and versatility in terms of applications. A model mini-house affixed with the ionogel-incorporated glazing demonstrates a reduction of indoor temperature by up to 20 °C far superior to state-of-the-art tungstate coated glazing. This new class of ionogels marks an important milestone in smart materials development for a range of applications including autonomous and climate-adaptable solar modulation window