Magnetic induction swing adsorption: an energy efficient route to porous adsorbent regeneration

Abstract

Metal−organic frameworks (MOFs) are promising nanomaterials with unprecedented capacity to store small molecules. Despite this huge capacity, proposed methods for releasing these molecules are not yet feasible at a meaningful scale, largely because of the strong binding of the molecules and the thermally insulating nature of the adsorbent. It is likely that large amounts of energy would be required for operation at scale. Furthermore, the high adsorption capacity of MOFs is not typically matched by a high working capacity; adsorbed molecules are not readily retrieved. Here we show a series of magnetic framework composites (MFCs) synthesized from ferri-magnetic MgFe2O4 nanoparticles and the Zr-based MOF UiO-66 can be deployed in a magnetic induction swing adsorption process for CO2 capture and release. Exposure of the MFCs to an alternating current magnetic field resulted in the generation of heat by the embedded magnetic nanoparticle and fast release of CO2 from the MOF, with an unprecedented 100% of adsorbed CO2 released under a 42 mT field. This was achieved at a regeneration time of 240 s. The efficiency of the MISA process was shown to be dependent on the amount of MFC used, with efficiencies reaching 60% at just a gram scale. These local “nanoheaters” overcome the thermally insulating nature of the adsorbent, which has promising implications for use at scale. Additionally, the ability to access 100% of the adsorption capacity permits the use of strongly adsorbing, high-capacity MOFs that were previously discarded.