Linker scissoring strategy enables precise shaping of Fe/Mn-MOF to construct an S-scheme heterojunction with Bi2S3 for enhanced photoexcitation under peroxymonosulfate activation

Abstract

Metal–organic frameworks (MOFs) with controllable shapes and sizes exhibit tremendous potential in environmental remediation. However, the synergistic effects between their shape and photocatalytic performance have not been fully established to date. Herein, a tailored strategy of ligand trimming through acetic acid-regulated solvothermal methods was successfully designed to develop controlled shapes of bimetallic Fe/Mn-MOF. This approach yielded hexagonal prismatic bipyramidal crystals (HPBC), quadratic bipyramidal crystals (QBC) and hexagonal platelet crystals (HPC). This work broke through the limitations of the traditional single-morphology regulation and effectively modulated the crystal growth rate, allowing for the formation of three MOF shapes. Nitrogen physisorption and photocatalytic experiments confirmed that QBC, with the smallest particle size, possessed the highest surface area and catalytic activity, indicating that a suitable particle size provided a higher number of active sites. Therefore, QBC with the optimal morphology was chosen for further study and integrated with Bi₂S₃ to construct an S-scheme heterojunction. This heterojunction facilitated efficient electron–hole separation and migration driven by the built-in electric field, significantly boosting the photocatalytic activity. Consequently, a superior 94.26% degradation efficiency for tetracycline was achieved within 40 min via photoexcitation. Based on both experimental results and DFT theoretical calculations, the non-radical oxidation (¹O₂) mechanism involved in the electrophilic attack toward peroxymonosulfate (PMS) activation was discovered. This study can guide the rational design of the structure–activity heterojunction catalysts.