Regulating Steric Hindrance in Redox-Active Porous Organic Frameworks Achieves Enhanced Sodium Storage Performance.

The development of novel redox-active polymers for sustainable sodium ion batteries (SIBs) has captured growing attention, but battery performance has been significantly limited by poor reversible specific capacities, where the majority of aromatic C6-benzene linkages are redox inactive. Here, a simple, yet efficient approach to improve sodium (Na) storage on these C6-benzene rings within a porous polymeric framework by rationally regulating their steric hindrance is reported. Decreasing intrinsic hindrance affords a significant improvement in redox reaction kinetics within the porous architecture, thereby facilitating the acceptance of Na ions on these functionalized benzene rings and boosting the SIB performance. As a result, the modulate porous framework exhibits an exceptional battery capacity of 376 mAh g-1 after 1000 cycles at 1.0 A g-1 , which is ≈1.5 times larger than that of the pristine framework. Furthermore, the performance can reach as high as 510 mAh g-1 at 0.1 A g-1 , comparable to that of the best-performing polymeric electrodes. The simple modulation approach not only enables Na storage modulation on functionalized C6-benzene rings, but also simultaneously provides a means to extend the understanding of the structure-property relationship and facilitate new possibilities for organic SIBs.