Induced‐Fit for Oxygen Adsorption: Flexible Conjugated Microporous Polymers With Self‐Adaptive Active Sites for H ₂ O ₂ Photosynthesis

Abstract

ABSTRACT Photocatalytic hydrogen peroxide (H 2 O 2 ) synthesis via oxygen reduction reaction (ORR) offers a sustainable alternative to energy‐intensive anthraquinone processes. However, its efficiency is hindered by poor selectivity and instability stemming from reactive superoxide intermediates through the two‐step two‐electron (2e − ) route. Herein, inspired by the “induced‐fit” mechanism of enzymes, a strategy of self‐adaptive active sites modulation using flexible conjugated polymers engineered with nonplanar linking units was proposed. The flexible conjugated microporous polymers facilitated a transition of O 2 adsorption from Pauling‐type to Yeager‐type. Among the designed polymers, CMP‐B4, which was constructed from 4,4′‐position‐coupled bipyridine units, exhibited optimal geometric matching capability for O 2 activation. Specifically, upon the approach of O 2 , the interaction between the lone‐pair electrons of nitrogen atoms in flexible bipyridine unit and π* orbitals of O 2 induced a dihedral rotation (e.g., approximately 10° in CMP‐B4), playing a key role in promoting the one‐step 2e − ORR pathway, thus overcoming the limitations of poor adaptability to diverse O 2 adsorption modes and restricted versatility of dual‐nitrogen units in the rigid nitrogen‐rich polymers. Such configuration of CMP‐B4 suppressed the formation of *OOH intermediates and achieved an excellent photocatalytic H 2 O 2 production rate of 6.21 mmol g −1 h −1 under continuous‐flow photocatalytic conditions over 24 h.