Construction of UiO-66-NH decorated by MoS QDs as photocatalyst for rapid and effective visible-light driven Cr(VI) reduction.

The photoactive metal-organic frameworks (MOFs) are good candidates for photocatalysts, but the quick electron-hole pairs recombination has greatly restricted the photocatalytic ability of MOFs. To improve the photoactivity of MOFs, MOFs-based composite materials have been extensively studied. Here, we successfully integrated MoS quantum dots (QDs) with UiO-66-NH for the first time under hydrothermal conditions. The as-prepared MoS QDs/UiO-66-NH (MS-U) had good visible light response ability (absorption edge at 445 nm), and charge separation and transfer ability, which lays the foundation for the photocatalytic Cr(VI) reduction. Photocatalytic studies revealed that MoS QDs-5/UiO-66-NH (MS-U-5) had superior Cr(VI) reduction activity than pure MoS QDs and UiO-66-NH. MS-U-5 could remove 98% Cr(VI) at pH= 2 with visible light irradiation for 20 min, which is the fastest visible light driven Cr(VI) reduction rate among the reported MOFs-based composite photocatalysts without the presence of any cocatalysts or scavengers as far as we know. Importantly, MS-U-5 could be reused at least three times. In the end, the possible electron transfer path and mechanism of Cr(VI) reduction was also investigated.