Porous Polyisothiocyanurates for Selective Palladium Recovery and Heterogeneous Catalysis

Abstract

Palladium (Pd) is an indispensable metal due to its wide range of industrial applications. Pd refining, however, is an extremely energy intensive process with a serious environmental impact. Thus, the selective recovery of Pd from secondary sources i.e., spent automotive catalytic converters, is rather important. Heterogeneous sorbents are promising candidates primarily due to their reusability, however, the simultaneous realization of high adsorption capacity, fast adsorption kinetics, high selectivity still remain a critical challenge. Here, we report the synthesis of porous polyisothiocyanurates, named Covalent Isothiocyanurate Frameworks (CITCFs), bearing in-situ generated thiourea moieties as binding sites for Pd. High surface area of CITCFs, 1589 m2 g-1, along with the presence of abundant sulfur atoms within a hierarchically porous network enabled an exceptional Pd(II) uptake capacity of 909.1 mg g-1, fast kinetics, stable adsorption over a wide pH range and selective Pd(II) recovery from waste water conditions. Moreover, the reduction of recovered Pd(II) within CICTFs led to a highly efficient heterogeneous catalysts for the Suzuki-Miyaura crosscoupling reaction.