Ab initio study: Investigating the adsorption behaviors of polarized greenhouse gas molecules on pillar[5]arenes

Supramolecular organic frameworks (SOFs) based on Pillar[5]arenes (P[5]A) have shown great potential in capturing and separating greenhouse gases. In this study, we investigate the adsorption behaviors of other environmentally harmful gas molecules, including NO, NH3, CO, and NO2 on pillar[5]arenes (P[5]A) using DFTB and DFT calculations. The P[5]A structures exhibit the capability to adsorb including NO, NH3, CO, and NO2 at both the cavity site and OH group, facilitated by π-π interactions and hydrogen bonding. CO exhibits the lowest binding energy among the studied gases, primarily due to its weak dipole moment. In contrast, the cavity-in positions for NO2 and NH3, characterized by high polarization, exhibit the highest adsorption energies. The adsorption energies at the top-out positions are relatively similar for all gases examined. These findings provide valuable insights for the targeted design and optimization of P[5]A, enabling its potential applications in effectively capturing toxic gases.