Theoretical calculations and photodegradation of methylene blue for three isostructural transition M2+ compounds expanded by 1,10-phenanthroline and SCN- under hydrothermal in situ reaction

Three isostructural transition M2+ compounds containing SCN- and 1,10-phenantroline (phen), [M(SCN)2(phen)2] (M2+ = Cd2+ 1, Mn2+ 2, Zn2+ 3), were synthesized under hydrothermal conditions. Noteworthily, the SCN- in the compounds were all originated from the in situ reaction of ligand. Although they were only mononuclear structure, they all further self-assemble into interesting supramolecular networks via π···π stacking of aromatic rings. The different interaction contacts of the molecule and the molecular packing strength in the compounds were investigated using Hirshfeld surface. The energy composition of these compounds was studied by energy framework. Meanwhile, the UV visible diffuse reflection of compounds 1-3 was also investigated. The photocatalytic activity toward methylene blue (MB) showed that the highest degradation efficiency reached 92.2% for 1, 86.3% for 2 and 93.7% for 3 at pH = 10, respectively. The photocatalytic stability of compound 1-3 was confirmed by cyclic experiments and PXRD analysis. The possible reaction mechanism was inferred based on the Radical trapping experiments and Mott–Schottky curve. Radical trapping experiments was conducted to determine the active species involved in the catalytic reaction.