title: 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.
authors.affiliation: Hydrogen and Energy Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology; nicholas.stadie@empa.ch.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Stadie
authors.affiliation: Hydrogen and Energy Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology.
authors.forename: Elsa
authors.initials: E
authors.lastname: Callini
authors.affiliation: Hydrogen and Energy Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology.
authors.forename: Philippe
authors.initials: P
authors.lastname: Mauron
authors.affiliation: Hydrogen and Energy Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology.
authors.forename: Andreas
authors.initials: A
authors.lastname: Borgschulte
authors.affiliation: Hydrogen and Energy Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology.
authors.forename: Andreas
authors.initials: A
authors.lastname: Züttel
mesh_terms: D001894:Borohydrides / Q000737:chemistry / Q000302:isolation & purification; D002245:Carbon Dioxide / Q000737:chemistry; D025924:Chromatography, Supercritical Fluid / Q000295:instrumentation / Q000379:methods*; D008274:Magnesium / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D011312:Pressure; D013696:Temperature
chemical_list: D001894:Borohydrides; D002245:Carbon Dioxide; D008274:Magnesium; D009584:Nitrogen