Resin modified MIL-53 (Fe) MOF for improvement of photocatalytic performance

Metal organic frameworks (MOFs) are fascinating materials for diverse applications due to their adjustability of aperture and structure. Herein, a three-dimensional iron-based MOF with BDC linker (BDC = 1,4-benzenedicarboxylate), commonly known as MIL-53(Fe), has been synthesized and successfully composited with anionic resin (Amberlite IRA 200) and cationic resin (Amberlite IRA 900) resulting solid composite photocatalysts, AMIL-53 (Fe) and DMIL-53(Fe), respectively. In the novel composite photocatalysts, bulky MIL-53(Fe) MOF solids are used as both a support to anchor the finely ground Amberlite IRA resin powders and as a visible light active component for the degradation of organic pollutants in water. In addition to being a traditional support, the resins here were used as a co-catalyst (with loading ration of the resin to MIL-53(Fe) is controlled around 20 wt%) to capture and transfer pollutant molecule from bulk solution into the active centers of the composited catalysts. Such an immobilization of the resins significantly alters MIL-53 (Fe) activity and degradation selectivity of dye pollutants; after 120 min of visible light illumination (λ ≥ 420 nm) removal yield of SRB (24%) by the bare MIL-53 (Fe) was apparently improved to 96% after MIL-53 (Fe) was modified by Amberlite IRA 900, DMIL-53(Fe). The tunable degradation order was demonstrated by employing AMIL-53 (Fe) for the selective degradation of cationic dyes while DMIL-53 (Fe) for the degradation of anionic dyes. Furthermore, the composites activity was optimized by controlling resin to MOF ratio during immobilization. Immobilization also improves ease of separation and recyclability of the original MOF. Especially, AMIL-53 significantly reduces iron ion leaching resulting in an enhanced stability. The photocatalytic mechanism under visible-light irradiation is also discussed.