Unraveling the transition of ZIF-67-on-ZIF-8 core-shell structured dodecahedron formed by an oriented attachment mechanism from type II to step-scheme for enhanced photocatalytic degradation of oxytetracycline hydrochloride

A composite photocatalyst comprising ZIF-67 and ZIF-8 was synthesized using a hydrothermal method. The process entailed the crystallization of ZIF-67 on the ZIF-8 dodecahedron backbone, eschewing the utilization of ligands. The photocatalytic efficiency of the composite ZIF-67-on-ZIF-8 was evaluated through the degradation of oxytetracycline hydrochloride (OTC) under visible and UV light. The results indicated superior OTC degradation compared to pure ZIF-8 and ZIF-67, which might be attributed to the energy level and lattice alignment between ZIF-8 and ZIF-67. This facilitated the separation and transfer of photogenerated electron-hole pairs, thereby suppressing electron-hole complexation. The activation of ZIF-67-on-ZIF-8 with peroxymonosulfate (PMS) resulted in a further enhancement in the degradation efficiency of OTC under both visible and UV light conditions. The optimal effect was observed with the addition of 0.6 mmol of PMS, which resulted in a degradation rate of 95.7 % at 60 min under visible light and 97.01 % at 30 min under UV light. The acceleration of the degradation process and the reduction in the required time were the result of a change in configuration. The study's originality led to the transformation of the conventional type II heterojunction model into the S-scheme heterojunction model through the modification of the light source, thereby offering a novel perspective for heterojunction design.