The structural, electronic and optical properties of transition metal doped porphyrin (TM@P; TM = Mn, Co, Fe, Cu, Ni, Zn) as well as the effect of CO adsorption on TM@P properties have been investigated using the density functional theory (DFT). The presented results include adsorption energies, bond lengths, electronic configurations, magnetic moments, density of states, frontier molecular orbitals, and UV-Vis. spectra. Our calculation results show that, the CO molecule favors to be adsorbed on TM-doped Porphyrin with its carbon head. The most energetically stable adsorption of CO is reported for Fe doped Porphyrin. The interaction between CO molecules with TM@P is attributed to donation-back donation as well as charge transfer mechanisms. Mn, Co and Fe-doped porphyrins have visible active nature which may be affected by CO adsorption, whereas, Ni, Cu and Zn-doped porphyrins have UV active nature which not affected by CO adsorption. These results may be meaningful for CO removal and detection.

Theoretical calculations based on the Density Functional Theory (DFT) have been performed to investigate the interaction of H₂S as well SO₂ gaseous molecules at the surfaces of Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages. The results show that a Mg₁₂O₁₂ nano-cage is a better sorbent than a Be₁₂O₁₂ nano-cage for the considered gases. Moreover, the ability of SO₂ gas to be adsorbed is higher than that of H₂S gas. The HOMO–LUMO gap (E_g) of Be₁₂O₁₂ nano-cage is more sensitive to SO₂ than H₂S adsorption, while the E_g value of Mg₁₂O₁₂ nano-cage reveals higher sensitivity to H₂S than SO₂ adsorption. The molecular dynamic calculations show that the H₂S molecule cannot be retained at the surface of a Be₁₂O₁₂ nano-cage within 300–700 K and cannot be retained on a Mg₁₂O₁₂ nano-cage at 700 K, while the SO₂ molecule can be retained at the surfaces of Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages up to 700 K. Moreover, the thermodynamic calculations indicate that the reactions between H₂S as well SO₂ with Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages are exothermic. Our results suggest that we can use Be₁₂O₁₂ and Mg₁₂O₁₂ nano-cages as sorbents as well as sensors for H₂S and SO₂ gases.