From Reticular Chemistry Design to Density Functional Theory Modeling for New Zeolitic Imidazolate Framework Topologies: Mechanical Stability, Electronic Structure, and CO₂ Selectivity

Adopting the knowledge and resource of reticular chemistry, we introduce a series of new zeolitic imidazolate framework (ZIF) structures within three topological categories, pth, pts, and ast, constructed by the square-planar and tetrahedral building blocks. Systematic metalation is considered with various cations (i.e., Ni2+, Cu2+, Mn2+, Co2+, Zn2+). Utilizing the advantage of density functional theory (DFT) calculations, we observe that the imidazole linking units suffer severe deformation in the ast and pts networks, as pointed out by the negative phonon modes. The mechanical stability is then verified by analyzing the elastic tensors (Cij), and we conclude four structures to acquire mechanical stability: pth-1 (NiMn), pth-2 (NiCo), pth-3 (NiZn), and pth-6 (CuZn). Electronic structure analysis suggests the first two structures to exhibit strong magnetism, whereas the latter are weakly or even nonpolarized, which establishes good agreement with the ligand-field theory prediction. The band gaps of those structures fall in the range of 0.74 to 1.78 eV, as estimated by conventional DFT calculations. Finally, we investigate the CO2 selectivity over N2 within pth-1 and pth-3 by conducting grand canonical Monte Carlo simulations for gas adsorption. For the pth-1 (NiMn) and pth-3 (NiZn) cases, the load of CO2 dominantly exceeds the uptake of N2 at the pressure up to 1 bar, indicating those structure to be promising in CO2 capture and selectivity