Bimetallic Metal-Acetylide Frameworks for Highly Selective and Durable H₂O₂ Electrosynthesis

Metal-acetylide frameworks (MAFs) feature tunable d-π orbital hybridization between transition metal centers and π-conjugated acetylide linkers. Here we report a two-dimensional (2D) MAF, ZnTTPP-Ni-AF, assembled from zinc-thienylporphyrin units (ZnTTPP) and nickel(II)-bis(acetylide) linkers (─C≡C─Ni(PBu₃)₂─C≡C─, Bu = ─CH₂CH₂CH₂CH₃), as a selective electrocatalyst for the two-electron oxygen reduction reaction (2e^- ORR) to H₂O₂. In alkaline electrolyte, ZnTTPP-Ni-AF achieves 94% H₂O₂ selectivity and >90% Faradaic efficiency (FE) in an H-cell, with excellent stability over 148 h. In a flow cell, it maintains >91% FE from 20 to 160 mA cm^-2, delivering an H₂O₂ yield rate of 13.68 mol g^-1 h^-1 at 160 mA cm^-2. Combined experimental and theoretical studies reveal that synergy between Zn-N₄ porphyrinic centers and Ni^II-bis(acetylide) motifs promotes O₂ activation and stabilizes the *OOH intermediate, steering the ORR toward the 2e^- pathway. Enhanced Ni-3 $d_{z^2}$ and O-2p orbital hybridization facilitates proton-coupled electron transfer to *OOH while suppressing O─O bond cleavage. This work demonstrates that engineering orbital hybridization and bimetallic cooperativity in MAFs provides an effective strategy to overcome the intrinsic activity-selectivity trade-off in electrocatalytic H₂O₂ synthesis.