Meso‐Substituent Engineering Tunes Co‐OOH Binding in Cobalt Porphyrins for Selective H 2 O 2 Electrosynthesis

ABSTRACT Cobalt porphyrins are prototypical molecular catalysts for two‐electron oxygen reduction to H 2 O 2 because of their well‐defined CoN 4 active sites and synthetically tunable ligand frameworks. However, conventional phenyl‐substituted cobalt porphyrins generally exhibit limited H 2 O 2 selectivity due to excessively strong Co‐OOH chemisorption, which can favor O─O bond activation and the competing four‐electron oxygen reduction pathway. Herein, we establish a meso‐substituent engineering strategy to regulate Co‐OOH interaction in cobalt porphyrins without altering the primary CoN 4 coordination motif. By progressively replacing meso‐phenyl groups with thienyl and bithienyl substituents, the optimized CoT 2 TP catalyst achieves a H 2 O 2 Faradaic efficiency of 98.4% together with a H 2 O 2 production rate of 74.96 mg cm −2 h −1 at 120 mA cm −2 . In situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) reveals a continuous blue shift of the O─O stretching vibration of adsorbed *OOH with increasing thiophene incorporation, indicating weakened Co‐OOH chemisorption and facilitated Co─OOH bond cleavage. Density functional theory calculations further show that bithienyl substitution shifts the Co d‐band center away from the Fermi level and optimizes the *OOH adsorption strength. This work establishes remote meso‐substituent regulation of Co‐OOH binding as a molecular design strategy for selective H 2 O 2 electrosynthesis.