AbstractWe have adopted the concept of “cage to frameworks” to successfully produce a Na–N connected coordination networked cage Na-NC1 by using a [3+6] porous imine-linked organic cage NC1 (Nanjing Cage 1) as the precursor. It is found that Na-NC1 exhibits hierarchical porosity (inherent permanent voids and interconnected channel) and gas sorption measurements reveal a significantly enhanced CO2 uptake (1093 cm3 g−1 at 23 bar and 273 K) than that of NC1 (162 cm3 g−1 under the same conditions). In addition, Na-NC1 exhibits very low CO2 adsorption enthalpy making it a good candidate for porous materials with both high CO2 storage and low adsorption enthalpy.

AbstractWe have adopted the concept of “cage to frameworks” to successfully produce a Na–N connected coordination networked cage Na-NC1 by using a [3+6] porous imine-linked organic cage NC1 (Nanjing Cage 1) as the precursor. It is found that Na-NC1 exhibits hierarchical porosity (inherent permanent voids and interconnected channel) and gas sorption measurements reveal a significantly enhanced CO2 uptake (1093 cm3 g−1 at 23 bar and 273 K) than that of NC1 (162 cm3 g−1 under the same conditions). In addition, Na-NC1 exhibits very low CO2 adsorption enthalpy making it a good candidate for porous materials with both high CO2 storage and low adsorption enthalpy.

Highly permeable and selective, as well as plasticization-resistant membranes are desired as promising alternatives for cost- and energy-effective CO2 separation. Here, robust mixed-matrix membranes based on an amino-functionalized zeolitic imidazolate framework ZIF-7 (ZIF-7-NH2) and crosslinked poly(ethylene oxide) rubbery polymer are successfully fabricated with filler loadings up to 36 wt%. The ZIF-7-NH2 materials synthesized from in situ substitution of 2-aminobenzimidazole into the ZIF-7 structure exhibit enlarged aperture size compared with monoligand ZIF-7. The intrinsic separation ability for CO2/CH4 on ZIF-7-NH2 is remarkably enhanced as a result of improved CO2 uptake capacity and diffusion selectivity. The incorporation of ZIF-7-NH2 fillers simultaneously makes the neat polymer more permeable and more selective, surpassing the state-of-the-art 2008 Robeson upper bound. The chelating effect between metal (zinc) nodes of fillers and ester groups of a polymer provides good bonding, enhancing the mechanical strength and plasticization resistance of the neat polymer membrane. The developed novel ZIF-7 structure with amino-function and the resulting nanocomposite membranes are very attractive for applications like natural-gas sweetening or biogas purification.

•The hydrothermal stability of ZIF-8 strongly depends on the zinc salts variations.•Samples synthesized from zinc acetate exhibit the highest hydrothermal stability.•ZIF-8 membrane is suitable for the separation of humidified C3H6/C3H8 mixtures.Zeolitic-imidazolate framework-8 (ZIF-8), a representative member of the ZIF class, have attracted extensive application in gas adsorption, membrane separation and catalysis. Since the discovery of ZIF-8, they are always synthesized from zinc nitrate. In this work, we evaluate the hydrothermal stability of ZIF-8 nanocrystals and polycrystalline membranes synthesized from four kinds of common zinc salts. Several physical techniques (X-ray diffraction, scanning electron microscope, and nitrogen adsorption) indicate that ZIF-8 nanocrystals derived from zinc acetate, rather than zinc nitrate, exhibit the highest hydrothermal stability. After immersed in water (∼3 wt%) at 80 °C for 10 days, nanocrystals derived from zinc acetate still could sustain ∼45% relative crystallinity, whereas those from zinc nitrate were transformed to amorphous products. The polycrystalline membrane derived from zinc acetate also exhibits the highest dynamic hydrothermal stability. This work is benefit to the synthesis of ZIF-8 materials for application in water-sensitive systems.

The polydimethylsiloxane (PDMS) coating penetrated into the underneath ZIF-8 polycrystalline membrane not only blocking the inter-crystalline defects but also hindering the flexibility of the ZIF-8 framework, resulting in an unusual and highly desired increase in the separation selectivity of the C3H6/C3H8 mixture under high feeding pressures.

•Thin ATP-Pebax film (~700 nm) composite membranes were successfully fabricated.•The CO2 permeance was 40-fold improved from the reduction of membrane thickness.•The gas permeability in ATP fillers were first achieved from adsorptive tests.•Optimized permeating parameters in mixed-gas permeation were also evaluated.Composite membrane with a thin selective layer on porous polymer substrate is more attractive than the asymmetric polymer membrane. In this study, a thin layer of attapulgite-poly(ether-block-amide) (ATP-Pebax) hybrid material was successfully deposited on a porous polyacrylonitrile (PAN) support to form a composite membrane. The poly[1-(trimethylsilyl)-1-propyne] (PTMSP) gutter layer plays the crucial role in decreasing the thickness of ATP-Pebax selective layer due to its superior hydrophobicity. A contact 2 wt% ATP-Pebax selective layer (~700 nm) was successfully deposited on the PAN support. The CO2 permeance on the composite membrane was significantly improved from 2.6 to 108 GPU, compared with the 2 wt% ATP-Pebax freestanding membrane. The ideal selectivity for CO2/N2 and CO2/CH4 were also enhanced by 35% and 16%, respectively. The gas permeability in ATP fillers were achieved by adsorptive measurements and validated by the generalized Maxwell model for ATP-Pebax hybrid materials. The effect of the feeding pressure and permeating temperature on both single and mixed gas permeation were examined. The separation performance on the composite membranes under dry and humidified-state feeding were also compared. The optimized separating performance of the thin ATP-Pebax composite membrane are attractive for potential applications like natural gas sweetening or biogas purification.

•DGC is developed to synthesize magnetically responsive MOF/Fe3O4 composites.•DGC simplifies synthetic procedures and minimizes solvent consumption.•The composites are used for adsorption desulfurization and denitrogenation.•The composites can be recycled efficiently by an external magnetic field.Selective adsorption by use of metal-organic frameworks (MOFs) is an effective method for purification of hydrocarbon fuels. In consideration that the adsorption processes proceed in liquid phases, separation and recycling of adsorbents should be greatly facilitated if MOFs were endowed with magnetism. In the present study, we reported for the first time a dry gel conversion (DGC) strategy to fabricate magnetically responsive MOFs as adsorbents for deep desulfurization and denitrogenation. The solvent is separated from the solid materials in the DGC strategy, and vapor is generated at elevated temperatures to induce the growth of MOFs around magnetic Fe3O4 nanoparticles. This strategy can greatly simplify the complicated procedures of the well-known layer-by-layer method and avoid the blockage of pores confronted by introducing magnetic Fe3O4 nanoparticles to the pores of MOFs. Our results show that the adsorbents are capable of efficiently removing aromatic sulfur and nitrogen compounds from model fuels, for example removing 0.62 mmol g−1 S and 0.89 mmol g−1 N of thiophene and indole, respectively. In addition, the adsorbents are facile to separate from liquid phases by use of an external field. After 6 cycles, the adsorbents still show a good adsorption capacity that is comparable to the fresh one.

The polydimethylsiloxane (PDMS) coating penetrated into the underneath ZIF-8 polycrystalline membrane not only blocking the inter-crystalline defects but also hindering the flexibility of the ZIF-8 framework, resulting in an unusual and highly desired increase in the separation selectivity of the C3H6/C3H8 mixture under high feeding pressures.

Continuous ZIF-67 polycrystalline membranes with effective propylene/propane separation performances were successfully fabricated through the incorporation of zinc ions into the ZIF-67 framework. The separation factor increases from 1.4 for the pure ZIF-67 membrane to 50.5 for the 90% zinc-substituted ZIF-67 membrane.