Preparation of Size-Selective Nanoporous Polymer Networks of Aromatic Rings: Potential Adsorbents for Hydrogen Storage

The preparation of nanoporous size-selective hypercrosslinked polymer networks containing 37−92% of pores small enough for hydrogen adsorption but too small to allow penetration of nitrogen has been studied. Polyaniline and diaminobenzene were coupled with diiodobenzene and tribromobenzene using Ullman and Buchwald synthetic routes. The resulting porous polymer networks consist of aromatic rings linked through a trivalent nitrogen atom. The Buchwald reaction appears to be more effective than the Ullman synthesis for the production of such materials. The use of solvents with higher Hildebrand solubility coefficients during synthesis affords polymers with higher surface areas. The nanoporous polymers possess unusually high initial enthalpies of adsorption of hydrogen reaching values of up to −18 kJ/mol.