Imidazolium-Based Porous Organic Polymers: Anion Exchange Driven Capture and Luminescent Probe of Cr2O72-

A series of imidazolium-based porous organic polymers (POP-Ims) was synthesized through Yamamoto reaction of 1,3-bis(4-bromophenyl)imidazolium bromide and tetrakis(4-bromophenyl)ethylene. Porosities and hydrophilicity of such polymers may be well tuned by varying the ratios of two monomers. POP-Im with the highest density of imidazolium moiety (POP-Im1) exhibits the best dispersity in water and the highest efficiency in removing Cr2O72-. The capture capacity of 171.99 mg g(-1) and the removal efficiency of 87.9% were achieved using an equivalent amount of POP-Im1 within 5 min. However, no Cr2O72- capture was observed using nonionic analogue despite its large surface area and abundant pores, suggesting that anion exchange is the driving force for the removal of Cr2O72-. POP-Im1 also displays excellent enrichment ability and remarkable selectivity in capturing Cr2O72-. Cr(VI) in acid electroplating wastewater can be removed completely using excess POP-Im1. In addition, POP-Im1 can serve as a luminescent probe for Cr2O72- due to the incorporation of luminescent tetraphenylethene moiety.