A Friedel−Crafts reaction was used to obtain covalent aromatic networks with high surface area and microporosity suited for CO2 and CH4 adsorption, even at low pressures. Starting from tetraphenylmethane and formaldehyde dimethyl acetal in different concentrations, the reaction yields porous polymers which were characterized with a wealth of experimental and computational methods. Thermogravimetry, infrared spectroscopy, and solid-state NMR were used to study the material structure. The pore distributions were measured by applying nonlocal density functional theory analysis to the adsorption isotherms of N2 at 77 K and Ar at 87 K (the latter being more suited for pore widths less than 10 Å). Carbon dioxide and methane were adsorbed at 273 and 298 K to evaluate the performance of these systems in gas capture, separation, and storage. A theoretical model of the porous network was defined to describe the ordered fraction of the material, with particular attention to ultramicropores. Ar, CO2, and CH4 adsorption in this model material was simulated by Monte Carlo techniques with a purposely optimized force field

The energy of three crystallographic faces of the PbSe lattice, with Miller indices (100), (110), and (111), is computed at the density functional theory level with a double-ζ polarized basis set. The addition energy of different organic ligands on the three faces is computed at the same level both in periodic infinite slabs and in finite clusters to explore the relative affinities and the possible modifications of the stability order of the faces. Neutral ligands are found to have the greatest affinity for (110), while propionate anion binds most strongly to (111) face: in the last case the stability order of the pure surfaces can be reversed by the presence of ligands. The prevalence of different faces is related to the shape of PbSe nanoclusters, and a model is proposed to explain the excess of Pb atoms found in nonstoichiometric clusters by some experiments.

A number of 2D layered perovskites A2PbI4 and BPbI4, with A and B mono- and divalent ammonium and imidazolium cations, have been modeled with different theoretical methods. The periodic structures have been optimized (both in monoclinic and in triclinic systems, corresponding to eclipsed and staggered arrangements of the inorganic layers) at the DFT level, with hybrid functionals, Gaussian-type orbitals and dispersion energy corrections. With the same methods, the various contributions to the solid stabilization energy have been discussed, separating electrostatic and dispersion energies, organic-organic intralayer interactions and H-bonding effects, when applicable. Then the electronic band gaps have been computed with plane waves, at the DFT level with scalar and full relativistic potentials, and including the correlation energy through the GW approximation. Spin orbit coupling and GW effects have been combined in an additive scheme, validated by comparing the computed gap with well known experimental and theoretical results for a model system. Finally, various contributions to the computed band gaps have been discussed on some of the studied systems, by varying some geometrical parameters and by substituting one cation in another's place.

Molecular crystals of dipeptides containing open channels can selectively absorb CO 2 over N 2 and CH 4 , as shown by experimental and simulated isotherms. The efficient CO 2 capture enabled separation from methane and allowed the direct observation by 2D MAS NMR of CO 2 sequestered in the peptide-based biozeolites.