Charge-Tunable Bismuth-Hydroxamate\nMetal–Organic\nFrameworks for Photocatalytic Cr(VI) Mitigation

This study presents three bismuth-hydroxamate metal–organic\nframeworks (MOFs), namely, SUM-90A/B/C (SUM = Sichuan University Materials),\nprepared from Bi<sup>3+</sup> and the same bridging ligand (1,4-benzenedihydroxamic\nacid). By varying the synthetic conditions, the charge states of the\nframework backbones and the coordination environments of the Bi<sup>3+</sup> centers were finetuned, resulting in distinct structures\nand properties. The performances of MOFs as heterogeneous photocatalysts\nfor Cr(VI) mitigation were comparatively studied, using both theoretical\nand experimental methods, and they exhibited remarkable kinetic stability\nin aqueous media and varied electronic structures. Specifically, SUM-90C,\nwith an experimental band gap of 1.92 eV, was identified as a promising\nphotocatalyst that could effectively convert Cr(VI) within 4 h and\nretain 96% of its capability over 3 cycles.