Preparation and characterization of melamine-based porous Schiff base polymer networks for hydrogen storage

Based on Schiff base chemistry, crosslinked porous organic aminal networks were prepared using acetic acid as a catalyst. These Schiff base networks (SNWs) are polymeric materials based on melamine and 5,5'-methylene bissalicylaldehyde, with nitrogen contents as high as ca. 36 wt.%, which were characterized by FTIR spectroscopy, elemental analysis, and ¹³C and ¹⁵N solid-state NMR spectroscopies. A series of polymer networks with different monomeric molar ratios and different amounts of added catalyst were explored, in order to study their effect on the final polymer structure, porosity and H₂ storage capacity. These materials exhibit Brunauer-Emmett-Teller (BET) surface areas up to ca. 526 m²/g, as measured by N₂ adsorption at 77 K, and exhibit gravimetric storage capacities up to 2.57 wt.% at 20 bar and 77 K.