Dual-functional ionic porous organic framework for palladium scavenging and heterogeneous catalysis

Abstract

Porous organic frameworks (POFs) with predesigned structures and tunable porosities have been widely studied in adsorption and heterogeneous catalysis. Introducing ionic structure into the framework endows POFs with new functionalities that may extend their applications. Here, we report new applications for a guanidinium-based ionic POF (IPOF-Cl) in palladium scavenging and heterogeneous catalysis. Due to the ionic framework and the porous structure, the IPOF-Cl displays fast adsorption kinetics and high adsorption capacities (up to 754 mg g⁻¹) of Na₂PdCl₄ in aqueous solutions via a chemisorption (ion exchange) process. Significantly, it shows excellent scavenging activity towards trace amount of [PdCl₄]²⁻ in aqueous solution. More importantly, the loaded [PdCl₄]²⁻ species on the IPOF substrate are further reduced into ultrafine Pd nanoparticles with size of ∼2–5 nm. The obtained IPOF-Pd(0) nanocomposite containing uniformly distributed Pd nanoparticles and hierarchical porous structure demonstrates high activity in catalyzing a range of Suzuki coupling reactions. This study provides new routes for the development of ionic porous organic materials for applications in metal scavenging and catalysis.