Accurate Computation of Gas Uptake in Microporous Organic Molecular Crystals

Microporous organic molecular crystals (MOMCs) are materials composed of discrete organic molecules interacting noncovalently. The gas uptake of CO2, CH4, N-2, and Xe in one of the most widely investigated MOMCs, trispiro(benzodioxole[2'.2:2 ''.4:2 '''.6]1,3,5,2,4,6-triazatriphosphinine) (1), was computed by grand canonical Monte Carlo (GCMC) simulations based on our lately developed force field method vdW3, which is fitted to accurate ab initio potentials (double hybrid functional B2PLYP with a D3 dispersion correction using def2-TZVPP basis sets). The B2PLYP-D3 results compare very well with CCSD(T)/CBS interaction energies for benzene-gas model complexes. Our multiscale modeling approach to accurate interaction potentials is found to be essential in order to obtain reasonable adsorption isotherms and heats of adsorption. The good agreement between the simulation results and experimental data in all cases gives us the opportunity to design novel complex materials for gas adsorption based solely on first-principles calculations.