Today's paper summary
comes from Meijun Li.
Metal-organic frameworks (MOFs), which are constructed from transition metal ions and bridging organic ligands, are a new family of nanoporous molecular sieves. MOFs with different microstructures and morphologies such as 1D, 2D, 3D, core-shell MOFS, etc. have been attractive for CO2 capture and separation. New discoveries are still being made constantly as the field is growing quickly. Yang et al. recently reported the preparation of 1-nanometer-thick sheets (molecular sieve nanosheets, (MSNs)) with large lateral area and high crystallinity from layered MOFs (Yang et al. Science 346, 1356 (2014)). They demonstrate their use in fabricating ultrapermeable membranes that have excellent molecular sieving properties for H2/CO2 separation. The paper reported for the first time the synthesis of 1 nm thick MSNs from MOFs. Built upon the MSNs, 5-nm membranes exhibit an anomalous proportional relationship between the permeance and selectivity for H2/CO2. They achieved a simultaneous increase in both permeance and selectivity by suppressing lamellar stacking of the nanosheets. It is interesting that Lamellar ordering of nano-sheets would block the permeation pathway for H2, but have only a slight effect on CO2 leakage.
Metal-organic frameworks (MOFs), which are constructed from transition metal ions and bridging organic ligands, are a new family of nanoporous molecular sieves. MOFs with different microstructures and morphologies such as 1D, 2D, 3D, core-shell MOFS, etc. have been attractive for CO2 capture and separation. New discoveries are still being made constantly as the field is growing quickly. Yang et al. recently reported the preparation of 1-nanometer-thick sheets (molecular sieve nanosheets, (MSNs)) with large lateral area and high crystallinity from layered MOFs (Yang et al. Science 346, 1356 (2014)). They demonstrate their use in fabricating ultrapermeable membranes that have excellent molecular sieving properties for H2/CO2 separation. The paper reported for the first time the synthesis of 1 nm thick MSNs from MOFs. Built upon the MSNs, 5-nm membranes exhibit an anomalous proportional relationship between the permeance and selectivity for H2/CO2. They achieved a simultaneous increase in both permeance and selectivity by suppressing lamellar stacking of the nanosheets. It is interesting that Lamellar ordering of nano-sheets would block the permeation pathway for H2, but have only a slight effect on CO2 leakage.
Related to our EFRC
center, we may adapt/modify the synthesis method reported in this paper to make
2D MOFs that can be used as a model system in both Thrust 2 and Thrust 4 for
understanding how the novel 2D materials interact with acid gases. The rich
tunability of the pore structure and surface functionalities of the 2D MOFs
offers tremendous opportunities for future study in adsorption and separation areas.
Great read! I've never read anything about MSNs before, so this was somewhat of an eye-opening read for me. Is the GPU usually reported in units of cm^3 cm^(-2) s^(-1) cmHg^(-1)? This just simplifies to distance/(second*pressure), right? I guess I just kind of thought the units looked weird, but I am also not incredibly familiar with GPU.
ReplyDeleteI think one of the most impressive parts of the paper is that they see a direct correlation in permeability and selectivity. I don't quite understand how the disordered stacking facilitates this, but I guess I have an idea how. Does anyone have a direct answer as to why disordered stacking has this affect?
Figures 3a,b are really cool, by the way. It looks like a blanket was laid on top of the Al2O3 support, which is incredible! They mention this feature as well, "The texture of the underlying alpha phase Al2O3 support is distinguishable, indicating a very thin layer of Zn2(bim) MSNs on the support."