Poly(1-vinylbenzyl trimethylammonium) Tetrafluoroborate Functionalized Graphene in Low Pressure CO2 Adsorption

Surface modification by functional moieties tunes the properties of carbon nanostructures and makes them suitable for specific applications. This study demonstrates the influence of poly(1-vinylbenzyl trimethylammonium) tetrafluoroborae (P[VBTMA][BF4]) functionalization on CO2 adsorption properties of graphene. The surface of graphene was non-covalently functionalized by P[VBTMA][BF4] and the carbon dioxide adsorption-desorption properties were determined at multiple sub-ambient pressures and temperatures. Polymerized ionic liquid (PIL) moieties form highly porous layer on graphene surface, which increases 14-28% of CO2 adsorption capacity of graphene. Adsorption isotherm models indicate that PIL functionalization increases the density of adsorption sites, which has relatively low adsorption energy compared to native adsorption sites. It is observed that PIL functionalization increases the adsorbate retention. However, isosteric heats of adsorption are calculated to be in physisorption range, suggesting ease of adsorbent regeneration. The change in entropy of the system indicates the reversible adsorption of CO2 on heterogeneous surface.