ChE Pirkey Seminar – “Recent Adventures with Porous Materials: Triggered Release and Anti-aging Membranes” by Dr. Matthew Hill (Monash University)
Metal Organic Frameworks (MOFs) show unprecedented capacity to store small molecules, however, the proposed methods to release these molecules are not yet feasible at a meaningful scale, largely due to the strong binding of stored molecules and the thermally insulating nature of the adsorbent. For example, carbon capture (and release and subsequent storage) from coal-fired power plants has been estimated to require between 25 and 40% of the energy output of the power plant though a more recent estimate was even higher. Whilst desorption from insulators such as zeolites has been overcome by the passing of hot gas through the bed, this is at an efficiency cost, and lowers the versatility of use. This problem is even more acute given the potential platform applications of MOFs where large flows of hot gas are often not at all possible. This presentation will describe the incorporation of metal nanoparticles within MOFs and the use of magnetic induction heating to release a series of stored molecules with unprecedented efficiency, known as magnetic induction swing adsorption (MISA). Magnetic induction is the most energy efficient means of heating, hence its widespread usage in domestic cooking. Its use within Metal Organic Frameworks, where we have been able to show they act as ‘nanoheaters’, overcomes the inherently thermally insulating nature and we have been able to release 100% of stored molecules. Further research has shown combination with light responsive moieties further increases the energy efficiency (MaLISA), and recently their energy efficiency record was broken with these materials.
Aging in super-glassy polymers such as poly(trimethylsilylpropyne) (PTMSP) prohibits it from being used in polymer membranes for separating gas mixtures. While these polymers are initially very porous and large amounts of gas can selectively pass through them, they quickly pack into a denser phase becoming much less porous and permeable. This age-old problem has been solved by the use of an ultraporous additive that allows PTMSP to maintain its low-density, porous initial state by absorbing a portion of the polymer chains within its pores, and holding them in position. This is the first time that this aging process has been stopped in PTMSP without diminishing its properties when prepared as a gas separation membrane. In fact, the membrane properties are enhanced with an additive, and over approximately one year of long-term measurements show that the performance is maintained.
The addition of a very specific porous microparticle forms an interwoven nanocomposite with PTMSP, freezing the structure and hence stopping the aging process, but doing so whilst increasing the permeability and maintaining the selectivity. Porous Aromatic Frameworks (PAFs) are carbon-based structures formed by the self-condensation of tetrahedral monomer nodes to establish an ultraporous array. The regular nanopores of around 1.2 nm diameter are attractive for the intercalation of polymer side-chain components when incorporated within the PTMSP matrix, thereby freezing the as-cast lower-density polymer structure in place and stopping the aging process. This mechanism is distinct from the enhanced permeability effect of non-porous nanoparticle and porous nanoparticle additions to PTMSP that prop open the polymer chains at the nanoparticle/polymer boundary but do not prevent aging.
Associate Professor Matthew Hill is an Australian Research Council Future Fellow and the Winner of a 2014 Australian Prime Minister’s Prize for Science. Matthew leads an interdisciplinary team of researchers that are actively involved with industry partners to bring exciting discoveries in the laboratory to market. He has 17 patents and more than 100 publications. He graduated from UNSW chemistry in 2006 with a PhD under Prof Robert Lamb and presently holds a joint position between Monash University and CSIRO.