Enhancing Photocatalytic Performance of NH₂-UIO66 by Defective Structural Engineering

Abstract

NH₂-UIO66 (NU) is a promising photocatalyst for the reduction of Cr(VI) to low-toxic Cr(III) driven by visible light under ambient conditions. However, the main limitation in this process is the inefficient ligand to metal charge transfer (LMCT) of photo-excited electrons, which is caused by inherent energy gap (ΔE _LMCT). This study synthesized the defective NU (NUX-H, where X is the molar equivalent of the modulator) with reduced ΔE _LMCT through linkers removal via acid treatment. The electronic structure of NUX-H was systematically investigated, and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms. Furthermore, they substantially lowered the energy of the unoccupied d orbitals (LUMO), which was beneficial to efficient LMCT, resulting in an improved photocatalytic activity of NUX-H toward high-concentration (100 mg/L) Cr(VI) reduction. Compared to NU with defect-free structure, the reducing rate of Cr(VI) was increased by 47 times. This work introduced an alternative strategy in terms of designing efficient photocatalysts for reducing Cr(VI) under ambient conditions.

Keywords

NH₂-UIO66 / Defective structure / Efficient LMCT / Photocatalysis / Cr(VI) reduction

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