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.