Modulating Local Electronegativity in Covalent Organic Frameworks for Host–Guest Oxygen Reduction

ABSTRACT Developing high‐performance metal‐free electrocatalysts for the oxygen reduction reaction remains a major challenge in sustainable energy conversion. Herein, we report a host–guest chemistry strategy based on metal‐free covalent organic frameworks (COFs) to significantly enhance the catalytic performance. Unlike conventional COFs that focus primarily on linkage chemistry or heteroatom doping, our approach explicitly leverages molecular‐level design to create tailored binding pockets within the COFs pores, enabling high selectivity and strong interactions with O 2 . A series of fluorene‐based COF hosts with systematically tuned electronegativity are designed and synthesized to strengthen molecular recognition and binding toward oxygen via tailored electronic and structural environments. The optimized material achieves a remarkable half‐wave potential ( E 1/2 , vs. RHE) of 0.78 V, among the highest reported metal‐free COF‐based catalysts. This exceptional performance originates from enhanced host–guest recognition, which effectively facilitates O 2 adsorption while optimizing the stabilization and subsequent dissociation of key reaction intermediates on the active site. Through a combination of in situ characterization and theoretical calculations, these host–guest interactions promote the optimized adsorption of intermediates and accelerate reaction kinetics. This study provides a new paradigm for the design of high‐efficiency metal‐free electrocatalysts through precise molecular recognition, opening avenues for advanced catalytic systems beyond conventional approaches.