Constructing the o-FCMP adsorbent as a redox-reactor to implement in situ regeneration of binding sites for selective capture of precious metals

Abstract

The finitude availability of binding sites of adsorbents presents considerable challenges for precious metals (PMs) recovery. Immobilizing precious metal ions to metal clusters via redox reaction offers a prospect strategy for managing the pathway of adsorbents construction. Herein, o-fluorination conjugated microporous polymer (o-FCMP) with –CC– binding sites is introduced as a redox-reactor for recycling PMs, achieving maximum capacities of 793.5 mg g−1 for Au(III) and 447.7 mg g−1 for Pd(II), which are 10.0 and 5.6 times higher than that of Ag(I). Characterizations indicate o-FCMP in mediating the reduction of Pd(II) and Au(III), and standard Gibbs Energy calculations reveal preferred reduction of Au(III) owing to the lowest energy requirement for the rate-limiting step. In addition to the stronger πδ+–πδ− interactions between the electron-deficient π bond of –CC– in o-FCMP and electron-rich π48δ- of AuCl3 than π58δ- of PdCl42−, it seems more conducive to mediate the formation of Au(0) for achieving the in situ regeneration of –CC– active centers. Competition experiments demonstrate that o-FCMP is capable of targeting capture of Au(III) in bimetallic system containing Au(III) and Pd(II). These findings shed light on an innovative idea of in situ regenerativity for designing efficient adsorbents for selective recovery of Au(III) in one step.