To date, only several microporous, and even fewer nanoporous, glasses have been produced, always via post synthesis acid treatment of phase separated dense materials, e.g. Vycor glass. In comparison, high internal surface areas are readily achieved in crystalline materials, such as metal-organic frameworks (MOFs). It has recently been discovered that a new family of melt quenched glasses can be produced from MOFs, though they have thus far have lacked the accessible and intrinsic porosity of their crystalline precursors. Here, we report the first glasses that are permanently, and reversibly porous toward incoming gases, without post synthetic treatment. We characterized the structure of these glasses using a range of experimental techniques, and demonstrate pores in the 4-8 angstrom range. The discovery of MOF-glasses with permanent accessible porosity reveals a new category of porous glass materials, that are potentially elevated beyond conventional inorganic and organic porous glasses, by their diversity and tunability.
Lithium is mainly extracted from brine and ores; however, current lithium mining methods require large amounts of chemicals, discharge many wastes, and can have serious environmental repercussions. Metal–organic framework (MOF)‐based membranes have shown great potential in lithium extraction due to their uniform pore sizes, high porosities, and rich host–guest chemistry compared to other materials. In this review, the processes and disadvantages of current lithium extraction technologies are introduced. The structure features and corresponding design strategy of MOFs suitable for Li+ ion separations are presented. Following, recent advances of polycrystalline MOF membranes, mixed matrix membranes, and MOF channel membranes for lithium‐ion separation are discussed in detail. Finally, opportunities for future developments and challenges in this emerging research field are presented.
Porosity loss, also known as physical aging, in glassy polymers hampers their long term use in gas separations. Unprecedented interactions of porous aromatic frameworks (PAFs) with these polymers offer the potential to control and exploit physical aging for drastically enhanced separation efficiency. PAF-1 is used in the archetypal polymer of intrinsic microporosity (PIM), PIM-1, to achieve three significant outcomes. 1) hydrogen permeability is drastically enhanced by 375 % to 5500 Barrer. 2) Physical aging is controlled causing the selectivity for H 2 over N 2 to increase from 4.5 to 13 over 400 days of aging. 3) The improvement with age of the membrane is exploited to recover up to 98 % of H 2 from gas mixtures with N 2 . This process is critical for the use of ammonia as a H 2 storage medium. The tethering of polymer side chains within PAF-1 pores is responsible for maintaining H 2 transport pathways, whilst the larger N 2 pathways gradually collapse.
Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4‐methyl‐2‐pentyne) (PMP), and polymers with intrinsic microporosity (PIM‐1) reduces gas permeabilities and limits their application as gas‐separation membranes. While super glassy polymers are initially very porous, and ultra‐permeable, they quickly pack into a denser phase becoming less porous and permeable. This age‐old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.
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