An Amine‐Functionalized Iron(III) Metal–Organic Framework as Efficient Visible‐Light Photocatalyst for Cr(VI) Reduction

The photocatalytic reduction of Cr(VI) is investigated over iron(III)‐based metal–organic frameworks (MOFs) structured as MIL‐88B. It is found that MIL‐88B (Fe) MOFs, containing Fe(3)‐μ(3)‐oxo clusters, can be used as photocatalyst for the reduction of Cr(VI) under visible light irradiation, which is due to the direct excitation of Fe(3)‐μ(3)‐oxo clusters. The amine‐functionalized MIL‐88B (Fe) MOFs (denoted as NH(2)–MIL‐88B (Fe)) shows much higher efficiency for the photocatalytic Cr(VI) reduction under visible‐light irradiation compared with MIL‐88B (Fe). It is revealed that in addition to the direct excitation of Fe(3)‐μ(3)‐oxo clusters, the amine functionality in NH(2)–MIL‐88B (Fe) can also be excited and then transferred an electron to Fe(3)‐μ(3)‐oxo clusters, which is responsible for the enhanced photocatalytic activity for Cr(VI) reduction. The enhanced photocatalytic activity for Cr(VI) reduction is also achieved for other two amine‐functionalized iron(III)‐based MOFs (NH(2)–MIL‐53 (Fe) and NH(2)–MIL‐101 (Fe)).