Rational design of novel metal-organic framework/Bi4O7 S-scheme heterojunction photocatalyst for boosting carbamazepine degradation

Public health and ecosystems are at risk due to the overuse and large discharge of pharmaceutical and personal care products (PPCPs) (e.g. carbamazepine). Herein, a MIL-68(In)-NH2/Bi4O7 S-scheme heterojunction was first prepared through a two-step route for efficient and environmentally friendly photocatalytic carbamazepine degradation. 1.0-MIL-68(In)-NH2/Bi4O7 displayed efficient photocatalytic performance, and the removal rate of 50 mg/L carbamazepine could reach 92.7% at 120 min, which was 3.6 and 2.9 times that of Bi4O7 and MIL-68(In)-NH2, respectively, under visible light. Using LC-MS analysis and Gaussian software calculations, the degradation path of carbamazepine was explored in detail. A series of photoelectrochemical experiments revealed the efficient transfer of photogenerated charges in 1.0-MIL-68(In)-NH2/Bi4O7 photocatalyst. The radical trapping experiments and ESR characterization suggested a reasonable S-scheme photocatalytic mechanism. In this heterojunction material, the excellent photocatalytic performance was attributed to the large surface area and S-scheme mechanism, which provides more active sites and separates the photogenerated charges rapidly.