Precisely tuning the electronic states of organic polymer electrocatalysts via thiophene-based moieties for enhanced oxygen reduction reaction

Optimizing molecular structures in oxygen reduction reaction (ORR) is crucial for enhancing catalytic efficiency and stability, particularly with respect to the effective adsorption and conversion of reaction intermediates. Sulfur-containing heterocyclic compound thiophene can precisely modulate the electronic states and local charge densities, thereby fine-tuning the adsorption and reactivity of microporous polymers, yet, it remains a largely unexplored area. Herein, thiophene-based building blocks featuring diversified linkers into a phenyl-containing model Ph-CMP are developed, affording the thiophene-fused BPT-CMP and the thiophene-linked BCT-CMP. The electron density and adsorption capacity of the frameworks are well regulated through condensation and connecting modification, showing excellent half-wave potentials compared to the reversible hydrogen electrode, surpassing even most metal-free polymer electrocatalysts. Through theoretical calculations and experimental results, we have validated that the thiophene-fused skeleton (BPT-CMP) triggers the activation of thiophene units, with the exposed pentatomic heterocyclic carbon atom (site-3) serving as the catalytic active site.