The Sonogashira–Hagihara coupling reaction is utilized to fabricate ethynyl-linked phthalocyanine (Pc) 2D conjugated polymers (CPs), affording the unprecedented heterometallic compound Fe_0.5Co_0.5Pc-CP and homometallic analogues MPc-CPs (M = Fe, Co) for comparison. It is confirmed that Fe and Co ions are well-defined/distributed with one metal ion encircled by four neighboring ions of the second metal in close proximity in the heterometallic conjugated polymer. Compared to the homometallic analogues, the bimetallic polymer Fe_0.5Co_0.5Pc-CP is more highly efficient for the oxygen reduction reaction (ORR), indicating that the interaction of Fe and Co ions may provide a synergistic effect on the activity. Fe_0.5Co_0.5Pc-CP exhibits similar ORR catalytic activity and superior stability compared to commercial Pt/C in alkaline media. Density functional theory calculations reveal that a fast 2 × 2e⁻ synergistic catalytic reaction pathway is essential for the excellent ORR in Fe_0.5Co_0.5Pc-CP.

Mixed phthalocyanine-porphyrin-based conjugated microporous polymers with Fe–N₄ active sites were fabricated with the origin of their ORR catalytic activity clarified.

Artificial photosynthesis of urea from NH₃ and CO₂ seems to remain still essentially unexplored. Herein, three isomorphic three-dimensional covalent organic frameworks with twofold interpenetrated ffc topology are functionalized by benzene, pyrazine, and tetrazine active moieties, respectively. A series of experiment results disclose the gradually enhanced conductivity, light-harvesting capacity, photogenerated carrier separation efficiency, and co-adsorption capacity towards NH₃ and CO₂ in the order of benzene-, pyrazine-, and tetrazine-containing framework. This in turn endows tetrazine-containing framework with superior photocatalytic activity towards urea production from NH₃ and CO₂ with the yield of 523 μmol g⁻¹ h⁻¹, 40 and 4 times higher than that for benzene- and pyrazine-containing framework, respectively, indicating the heterocyclic N microenvironment-dependent catalytic performance for these three photocatalysts. This is further confirmed by in-situ spectroscopic characterization and density functional theory calculations. This work lays a way towards sustainable photosynthesis of urea.