Conjugated Microporous Polymer with Matched Energy Band Structure As Photocatalyst for Simultaneous Removal of Heavy Metal Ion and Organic Pollutant

The use of efficient photocatalysts to remove mixed pollutants from wastewater is of significance for environmental remediation. In this work, a novel conjugated microporous polymer (TAPP-PD-CMP) was synthesized and applied as a visible light driven photocatalyst to simultaneously remove a heavy metal ion and an organic pollutant. TAPP-PD-CMP possesses a large specific surface area (375 m2 g-1), narrow band gap (1.76 eV) and good chemical and thermal (similar to 450 degrees C) stabilities. More importantly, the energy band structure of TAPP-PD-CMP (ELUMO = 0.23 eV and EHOMO = 1.99 eV) enables adequate band edge potentials for photoreduction of a heavy metal ion (Cr(vi)) and photooxidation of an organic pollutant (RhB). Experimental results demonstrate that TAPP-PD-CMP has excellent adsorption-photocatalytic performance towards Cr(vi) (90%, 3 h) and RhB (94%, 3 h) from mixed contaminant wastewater at the same time. Additionally, TAPP-PD-CMP, as an environmentally-friendly photocatalyst, exhibits recyclability and sustainability. Radical trapping experiments reveal a synergistic photocatalytic mechanism, and the excellent photocatalytic activity is ascribed to continuous consumption of electrons and holes, reducing the recombination of photo-generated electron-holes. This work provides a promising CMP photocatalyst and an idea based on energy band engineering to design suitable photocatalysts for mixed pollutant treatment. A novel conjugated microporous polymer (TAPP-PD-CMP) with adequate band-edge position for photo-reduction and photo-oxidation reaction was synthesized. The cooperative photocatalytic mechanism was elucidated.