Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

Abstract

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml -1, modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 Å. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride. Video LinkThe video component of this article can be found at

HPM Live μ for a full CLEM workflow

“…With this proprietary technology we reach LN2 temperature and 2000bars in only 2ms, making our HPF system the fastest available up to date. We note that while the theoretical value for LN2 at 2000 bar is 113K, the LN2 working temperatures of HPMs in fact can reach 133K, the difference being attributed to the high density of LN2 and friction during application of the high-speed LN2 jet (Shimoni & Müller, 1998;Stadie, Callini, Mauron, Borgschulte, & Züttel, 2015;Studer, Michel, Wohlwend, Hunziker, & Buschmann, 1995).…”

Kinetic Barriers and Microscopic Mechanisms of Noble Gas Adsorption by Nanoporous γ‐Mg(BH4)2 Obtained by Means of Sub‐Second X‐Ray Diffraction

“…Communications of these particles belongs to the porous g-Mg(BH 4 ) 2 and another one apparently is the amorphous polymorph of Mg(BH 4 ) 2 , suggested by the Refs. [41,44] and our volumetric data. This makes impossible to get the correlations between particle size of g-Mg(BH 4 ) 2 and Kr uptake time and requires additional studies for the conditions of its shape/size and yield control.…”

Kinetic Barriers and Microscopic Mechanisms of Noble Gas Adsorption by Nanoporous γ‐Mg(BH4)2 Obtained by Means of Sub‐Second X‐Ray Diffraction

“…Zuschriften of these particles belongs to the porous g-Mg(BH 4 ) 2 and another one apparently is the amorphous polymorph of Mg(BH 4 ) 2 , suggested by the Refs. [41,44] and our volumetric data. This makes impossible to get the correlations between particle size of g-Mg(BH 4 ) 2 and Kr uptake time and requires additional studies for the conditions of its shape/size and yield control.…”