Regulating Steric Hindrance in Difunctionalized PAFs for Selective Separation of Pb(II)

Abstract

Efficient and selective removal of Pb(II) from wastewater with complex matrix remains a challenging task. Porous aromatic frameworks (PAFs) with tailoring strategies of performance from predesigned functional building blocks provide a favorable platform for selective separation of Pb(II). Herein, the bifunctional SPAFs with introduction of -OH and -SO3H were synthesized through rationally optimizing the number of active sties and regulating their steric hindrance. As a result, the modulate SPAF-0.75 exhibits favorable adsorption capacity of Pb(II) (212.34 mg g-1), which is 22 times larger than pristine framework. Effects of various heavy metal ions are investigated for capture of Pb(II) onto as-prepared adsorbents, SPAF-0.75 achieve the maximum selectively adsorption capacity of Pb(II) with the coexisting of Cu(II), Co(II), Ni(II), Cd(II), Zn(II). SPAF-0.75 is regenerated by thiourea/nitric acid and the removal rate still retain at 100% after six successive cycles. Furthermore, the surface electrostatic potential distribution via DFT calculation and XPS were performed to indicate that -OH and -SO3H were co-participate in the process of capturing Pb(II) on SPAF-0.75, and reveal SPAF-0.75 preferred removal of Pb(II) owing to the lowest adsorption energy (ΔEab = –3.99 eV). This study extend the understanding of the structure-property relationship and facilitate new possibilities for PAFs.

Keywords: Pb(II), Selective separation, SPAF adsorbent, Bifunctions, Steric hindrance regulation