Constructing Sari-Topology Covalent Organic Frameworks from Pseudo-C₅-Symmetric Core for Enhanced Oxygen Reduction...

Developing new topologies for two-dimensional covalent organic frameworks (2D COFs) remains challenging due to the scarcity of geometrically comparable building blocks. Herein, we report the construction of COFs exhibiting an unprecedented topology (named as sari) using a pseudo fivefold symmetric building block. The synthesized COFs, TTCD-DA-COFand TTCD-BA-COF, demonstrate high crystallinity, substantial surface areas, unique trapezoidal pores, and high electrocatalytic activity for the oxygen reduction reaction (ORR). Remarkably, without additional heteroatom doping or metal incorporation beyond the intrinsic imine nitrogen, both COFs exhibit favorable ORR performance.The TTCD-DA-COF (shorter linker) achieves superior ORR performance compared to TTCD-BA-COF (longer linker), featuring an onset potential (E_O) of 0.85 V, a half-wave potential (E_1/2) of 0.78 V, and a turnover frequency (TOF) value of 0.013 s^-1 at a potential of 0.75 V. Theoretical calculations attribute this enhanced activity to the easier formation of an OOH* intermediate on specific carbon atoms within the imine-linkages of TTCD-DA-COF. This work not only expands the COF structures but also establishes a novel strategy for designing highly efficient metal-free electrocatalysts through linker-modulated electronic control.