Dual-strategy enabled Bi-doped MOF-derived In2S3 hollow nanotubes for high-performance photocatalytic reduction of Cr(VI).

With the accelerated development of industry, the contamination of Cr(VI)-containing wastewater has attracted increasing attention. Photocatalytic technology was recognized as a promising candidate for sorting out this problem. This work introduced an innovative approach involving the doping of bismuth (Bi) into the NH2-MIL-68(In) crystal framework, followed by sulfidation to fabricate a series of Bi-doped MOF-derived In2S3 hollow nanotubes for photocatalytic Cr(VI) reduction. Under the dual strategy of metal doping and morphology control, 4 % Bi-In2S3 exhibited exceptional Cr(VI) reduction activities, achieving a 96.2 % reduction rate rapidly within 25 min. Meanwhile, the apparent kinetic constant of the optimized sample toward Cr(VI) photoreduction was 2.87 times higher than that of In2S3. The morphological properties and mechanism behind this were explored through detailed characterization and DFT (Density functional theory) calculations, indicating that Bi doping narrowed the bandgap and improved light utilization, and both the electrons and the ·O2- radicals were involved in the photocatalytic reaction, which led to the efficient conversion of Cr(VI) to Cr(III).