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.贵金属的可持续回收对于保障战略资源供给、降低采矿行业环境足迹均至关重要。其中，从电子废弃物中选择性回收金是一项兼具应用吸引力与技术挑战的目标。本研究报道了基于吩嗪的多孔四氧杂[8]环烯（PpTOC）的合成，该材料引入杂环冠醚官能团以实现高效金捕集。该PpTOC兼具超过1200 m²·g⁻¹的高比表面积、类氮杂冠醚空腔结构与高杂原子含量，在酸性条件下可实现高达860 mg·g⁻¹的金吸附容量。值得注意的是，即便在铜等高浓度竞争金属离子共存的体系中，该聚合物仍可从电子废弃物中选择性回收金。回收得到的负载有Au(III)、Au(I)与Au(0)混合物种的材料，可直接作为多相催化剂应用于串联烷基化-环化反应。尤为关键的是，仅通过更换溶剂，将非质子溶剂甲苯替换为质子溶剂乙醇，即可改变该多相催化剂的反应路径，使反应产物从烷基化产物转向环化产物，实现同一多相催化剂下的差异化产物选择性。