Improved thermal management in HKUST-1 composites upon graphite flakes incorporation: Hydrogen adsorption properties

Abstract

HKUST-1-based composites have been synthesized through the incorporation of synthetic graphite flakes in the MOF synthesis media. The presence of flakes gives rise to high quality HKUST-1 crystals, combining different morphologies (octahedral-shape crystals, cauliflower-shape crystals and truncated pyramids). The incorporation of graphite in the composites improves the structural stability of the embedded nanocrystals upon a conforming step at 377 kg/cm2 (0.5 tons), with limited structural damage (below 10% BET surface area reduction as compared to the 40% observed for pure HKUST-1). Furthermore, composites exhibit a significant improvement in thermal management, associated with the excellent thermal and electrical properties of the graphite microdomains incorporated. The improved stability of the composites is also reflected in the adsorption performance for hydrogen at atmospheric pressure and cryogenic temperatures, with a significant preservation of the adsorption properties (gravimetric capacity, <15% decrease vs powders) in the monoliths containing graphite. The best adsorption performance is achieved with sample HKUST-1@10GF, in monolithic form, with a volumetric excess uptake at 0.1 MPa and −195 °C close to 18.7 g/L. This value is among the best described in the literature for monolithic MOFs under similar adsorption conditions.