Abstract
Schwarzites, due to their high porosity, are among prospective materials for the sorption of different gases, including hydrogen. Their surface possesses negative Gaussian curvature that intimately determines how many carbon atoms each hydrogen molecule will interact with, which, in turn, defines the fraction of hydrogen that would be sorbed in the schwarzite. The critical question about contributions to the sorption of the surface topology and electronic effects is solved here. Within the framework of the QTAIM theory, the topological parameters of the electron density distribution function at the bond critical points characterizing the dispersion interaction of the H2 molecule with the carbon surface are estimated. On the example of molecules [6]circulene and [7]circulene, it was shown that, despite the electronic effects arising from the bending of this surface, on average, the energy of physical sorption of hydrogen obtained using MP2 calculations changes insignificantly - by about 0.1 kJ/mol in the case of, for example, vertical orientation of the molecule. By calculating the thermochemical properties by the PM6-D3 method, the dependence of the weight fraction of hydrogen sorbed in P216-schwarzite on the external gas pressure and the temperature has been established. In particular, it was shown that at 300 K and 10 MPa, this value is 4.6%, slightly higher than other carbon nanostructures with similar density, porosity, and accessible surface area values.
NSTL
Elsevier