Realization of stable and industrial-level H₂O₂ electroproduction still faces great challenge due large partly to the easy decomposition of H₂O₂. Herein, a two-dimensional dithiine-linked phthalocyaninato cobalt (CoPc)-based covalent organic framework (COF), CoPc-S-COF, was afforded from the reaction of hexadecafluorophthalocyaninato cobalt (II) with 1,2,4,5-benzenetetrathiol. Introduction of the sulfur atoms with large atomic radius and two lone-pairs of electrons in the C-S-C linking unit leads to an undulated layered structure and an increased electron density of the Co center for CoPc-S-COF according to a series of experiments in combination with theoretical calculations. The former structural effect allows the exposition of more Co sites to enhance the COF catalytic performance, while the latter electronic effect activates the 2e⁻ oxygen reduction reaction (2e⁻ ORR) but deactivates the H₂O₂ decomposition capability of the same Co center, as a total result enabling CoPc-S-COF to display good electrocatalytic H₂O₂ production performance with a remarkable H₂O₂ selectivity of >95% and a stable H₂O₂ production with a concentration of 0.48 wt% under a high current density of 125 mA cm⁻² at an applied potential of ca. 0.67 V versus RHE for 20 h in a flow cell, representing the thus far reported best H₂O₂ synthesis COFs electrocatalysts.

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.

It is a significant challenge to develop a high-efficiency synthetic methodology to access fully conjugated 2D conjugated polymer (CP)/covalent organic framework (COF) nanosheets (NSs) that have great application potential for electronics and energy. Herein, we report the exfoliation of a series of amorphous ethynyl-linked phthalocyanine (Pc) CPs (MPc-CPs, M = Fe, Co, Fe_0.5Co_0.5) into ultrathin MPc-CP NSs. Random coupling between the four regioisomers (with D_4h, D_2h, C_2v and C_s symmetry) of the two tetra-β-substituted phthalocyanine precursors endows the resulting phthalocyanine conjugated polymers MPc-CPs with intrinsic structural defects and a disordered framework on individual layers. This in turn induces a diminished interlayer overlapping and a weakened interlayer π–π stacking interaction, facilitating the possible exfoliation of MPc-CPs into ultrathin 2D NSs with a yield of over 50%. The direction observation by transmission electron microscopy (TEM) and atomic force microscopy (AFM) demonstrates that the ultrathin MPc-CP NSs possess a smooth surface with a uniform thickness of 1–3 nm and a lateral size of hundreds of nanometers. The as-prepared bimetallic Fe_0.5Co_0.5Pc-CP NSs were further used to fabricate a heterostructure Fe_0.5Co_0.5Pc-CP NS@G with graphene NSs as an oxygen reduction reaction (ORR) catalyst, which exhibits an onset potential of 1006 mV and a half-wave potential of 927 mV in 0.1 M KOH, representing one of the best values in an alkaline medium. Moreover, the excellent ORR activity of the exfoliated tetrapyrrole-based conjugated NSs hybridized with graphene has also been demonstrated by a Zn–air battery device, showing an open circuit voltage of 1.34 V and a peak power density of ca. 180 mW cm⁻².