17Mixed Matrix Membranes (MMMs) for gas separation applications, have enhanced selectivity when 18 compared with the pure polymer matrix, but are commonly reported with low intrinsic permeability, 30The current default technology for large scale CO 2 capture and storage (CCS) is based on liquid 31 phase absorption towers; whilst many projects of this sort are proposed, few reach completion as 32 costs become prohibitive 3 . Therefore, it is imperative to offer more cost-effective technological 33 solutions. Membrane separation is often considered; however, current commercial membrane 34 technologies are virtually as expensive as adsorption technologies. This is because gas fluxes 35 through selective membranes are so low that hundreds of millions of m 2 of commercial membranes 36 are required even for a single 1000MW power station 5 . When combined with membrane costs of 37 ~$50/m 2 , the capital cost for commercial membrane based solutions to CCS is not that different 38 from the unpalatably high costs of adsorption towers for CCS. The key to a future membrane based 39 2 CCS solution lies in significantly reducing the total membrane areas required, which in turn 40 requires cheap, higher permeability membrane materials that retain a high selectivity. New research 41 is aimed at developing better performance polymers (in selectivity and permeability); however the 42 timelines for reducing costs of such polymers may not be compatible with needs to find immediate 43 candidate materials for large scale membrane based CCS solutions. 44Typically, commercial membrane materials have low permeability of a few tens of Barrers 45(1 Barrer = 10 10 cm 3 (STP) cm cm 2 s 1 cmHg 1 ), but have acceptable selectivity for CO 2 removal 46 from flue-stack or natural gas sources. Merkel and co-workers 5 have shown it is imperative to 47 generate materials with orders-of-magnitude enhanced permeability whilst maintaining such 48 selectivity, to cost-effectively process the massive volumes of flue gas in power plants. 49 Microporous materials used for membrane technology potentially include inorganic and organic 50 frameworks, such as zeolites 7 , metal-organic frameworks (MOFs) 8 and covalent organic 51 frameworks 9 . However, commercial membranes units contain thin films of the selective material 52 where practical processability and physical durability requirements tend to favor the use of tough 53 polymeric thin films. Gas transport in most polymers can be explained with the solution diffusion 54 model, where the permeability coefficient (P) is a product of solubility (S) and diffusion coefficient 5510 . Polymers of Intrinsic Microporosity (PIMs) 11,12 , are a sub-class of microporous polymers 56 with a rigid, contorted backbone structure (for example, PIM-1 in Figure 1) and high intrinsic 57 permeabilities (e.g. P CO2 ~ 3000 Barrer), but with low selectivity compared to commercial polymers 58 (30-50 for CO 2 /N 2 separations) 13 . Thermal and other post-processing of PIM-1 and other polymers 59 such as TR-polymers 14 leads ...

Confinement of polymers in nano-spaces can induce unique molecular dynamics and properties. Here we show molecular weight fractionation by the confinement of single polymer chains of poly(ethylene oxide) (PEO) in the one-dimensional (1D) channels of crystalline pillar[5]arene. Pillar[5]arene crystals are activated by heating under reduced pressure. The activated crystals are immersed in melted PEO, causing the crystals to selectively take up PEO with high mass fraction. The high mass fractionation is caused by the greater number of attractive CH/π interactions between PEO C-H groups and the π-electron-rich 1D channel of the pillar[5]arene with increasing PEO chain length. The molecular motion of the confined PEO (PEO chain thickness of ~3.7 Å) in the 1D channel of pillar[5]arenes (diameter of ~4.7 Å) is highly restricted compared with that of neat PEO.

Inactivation of diol dehydratase during the glycerol dehydration reaction is studied on the basis of quantum mechanical/molecular mechanical calculations. Glycerol is not a chiral compound but contains a prochiral carbon atom. Once it is bound to the active site, the enzyme adopts two binding conformations. One is predominantly responsible for the product-forming reaction (G(R) conformation), and the other primarily contributes to inactivation (G(S) conformation). Reactant radical is converted into a product and byproduct in the product-forming reaction and inactivation, respectively. The OH group migrates from C2 to C1 in the product-forming reaction, whereas the transfer of a hydrogen from the 3-OH group of glycerol to C1 takes place during the inactivation. The activation barrier of the hydrogen transfer does not depend on the substrate-binding conformation. On the other hand, the activation barrier of OH group migration is sensitive to conformation and is 4.5 kcal/mol lower in the G(R) conformation than in the G(S) conformation. In the OH group migration, Glu170 plays a critical role in stabilizing the reactant radical in the G(S) conformation. Moreover, the hydrogen bonding interaction between Ser301 and the 3-OH group of glycerol lowers the activation barrier in G(R)-TS2. As a result, the difference in energy between the hydrogen transfer and the OH group migration is reduced in the G(S) conformation, which shows that the inactivation is favored in the G(S) conformation.