Thiol-functionalized PIM-1 for removal and sensing for mercury (II)

Polymers of intrinsic microporosity (PIMs) are a class of microporous polymers with rigid and contorted molecular structures. The special structures lead to incomplete space occupation, and the pores of PIMs originate from the formed void. In this work, we made attempts to expand the applications of PIMs to the aspect of heavy metal removal. First, PIM-1 was synthesized using tetrafluoroterephthalonitrile (TFTPN) and 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI) as precursors. The primary PIM-1 was quite hydrophobic, and thus could not be evenly dispersed in water, resulting in low adsorption capacity for mercury ions (Hg2+). A conversion of nitrile group in PIM-1 to thiol group was then carried out by two steps, namely carboxylation and introduction of thiol groups. The carboxylation made the polymers more active, and the final thiol-functionalization provided the polymers with hydrophilicity and affinity for Hg2+. The thiolethyl modified PIM-1 (assigned as PIM-G) and thiophenyl modified (assigned as PIM-B) possessed maximum Hg2+ adsorption capacity of 136 mg g(-1) and 127 mg g(-1) at pH 5, respectively. Besides, the thiol-functionalized PIMs had fluorescence property and showed potential in sensing for Hg2+.