Porous Phenazine-bridged Tetraoxa[8]circulenes for Selective Gold Recovery and Heterogeneous Catalysis

The sustainable recovery of precious metals is critical for securing strategic resources while reducing the environmental footprint of mining. Among these, the selective recovery of gold from electronic waste represents a particularly attractive yet challenging target. Herein, we report the synthesis of phenazine-based porous tetraoxa[8]circulene, PpTOC, incorporating heterocyclic crown ether moieties for efficient gold capture. The PpTOC combines a high surface area over 1200 m² g⁻¹ with aza-crown ether-like cavities and high heteroatom content, enabling high gold uptake capacities of up to 860 mg g⁻¹ under acidic conditions. Importantly, the polymer demonstrates selective recovery of gold from electronic waste even in the presence of high concentrations of competing metal ions such as copper. The recovered material, containing a mixture of Au(III), Au(I), and Au(0) species, has been directly employed as a heterogeneous catalyst in a sequential alkylation-annulation reaction. Critically, switching from aprotic toluene to protic ethanol redirects the reaction outcome from alkylation to annulation, enabling divergent product selectivity using the same heterogeneous catalyst simply by changing the solvent.