In situ growth of UIO-66-NH2 on thermally stabilized electrospun polyacrylonitrile nanofibers for visible-light driven Cr (VI) photocatalytic reduction

UIO-66-NH2 was successfully deposited on electrospun polyacrylonitrile (PAN) nanofibers treated by thermal oxidative stabilization (TOS) via a simple and effective in situ growth method. Owing to the formation of acridone rings, naphthyridinering rings and hydronaphthyridine rings during the TOS process, the thermally stabilized electrospun PAN (TSPAN) nanofibers were greatly improved in stability and heat resistance and could provide adequate nucleation points for MOFs growth, indicating an ideal MOFs deposition support without additional surface modifications. The results demonstrated that UIO-66-NH2 crystals distributed relatively uniform and dense on the TSPAN nanofibers with mass loading up to 28.1 wt%. Compared with powdered UIO-66-NH2, the formed UIO-66-NH2@TSPAN nanofibers showed enhanced visible light driven photocatalytic activity towards reduction of Cr(VI) due to the improvement of visible light response, more excellent photothermal conversion ability and the increase of exposed active sites. The photocatalytic reduction rate of Cr(VI) over UIO-66-NH2@TSPAN was up to 93% within 180 min and the rate constant (k = 0.1362) was 2.3 times that of powdered UIO-66-NH2 (k = 0.00576). Significantly, the mechanical flexibility and structural stability endowed the nanofibrous photocatalyst easy operation and outstanding reusable capability. The photocatalytic activity for Cr(VI) reduction still preserved 90% after five cycles. This work proposes a facile strategy for preparation of free-standing MOFs nanofibers and provides MOFs-based photocatalysts a new opportunitie for broad applications in water treatment.