Cr-metal-organic framework coordination with ZnIn2S4 nanosheets for photocatalytic reduction of Cr(VI)

MIL-101(Cr)@ZnIn2S4 hierarchical heterojunction was delicately designed and fabricated through the in-situ growth of ZnIn2S4 on MIL-101 and electrostatic self-assembly. It is affirmed that the Cr-S interface bonding between MIL-101 and ZnIn2S4 in their composite was established based on the characterization results of X-ray photoelectron spectroscopy, Raman and zeta potential. Thus, a high-speed channel for charges transfer is offered due to the Cr-S bond, intimate interface contact and hierarchical structure of MIL-101@ZnIn2S4, which largely inhibits the recombination of photo-induced charge carriers and promises a remarkable photocatalytic activity. Choosing visible-light-driven reduction of Cr(VI) as a model, the optimal MIL-101@ZnIn2S4 sample can reduce 95% of Cr(VI) within 30 min, corresponding to a rate constant of 0.107 min(-1), which is 2.9-fold compared with blank ZnIn2S4 counterpart (MIL-101 has a negligible performance). Additionally, a conspicuous apparent quantum yield of 9.7% can be achieved at a wavelength of 420 nm. Eventually, to reinforce the practicability of MIL-101@ZnIn2S4, the composite powders were manufactured as aerogels utilizing bacterial cellulose as a substrate. The MIL-101@ZnIn2S4 aerogel still exerts an enviable performance for photocatalytic reduction of Cr (VI) and stability. This work could inspire the material design and environmental remediation based on MOFs.

Automated summary

MIL-101(Cr)@ZnIn2S4 hierarchical heterojunction was fabricated through in-situ growth of ZnIn2S4 on MIL-101 and electrostatic self-assembly. The hierarchical structure provides a high-speed channel for charge transfer, inhibiting the recombination of charge carriers and promoting remarkable photocatalytic activity.