Ammonium-Ion Induced Redox Charge Storage of Porous Organic Polymer

By the virtue of rigid structures owing to covalent bonding, conjugated porous polymers (CPPs) exhibit fascinating physicochemical properties with a wide spectrum of applications. Despite chemical robustness, the electrochemistry of CPPs in various electrolytes of different pH is underexplored. Herein, we report a porous organic polymer- benzoperylene anhydride based conjugated porous polymer (BPA-CPP) with a rare combination of porosity and redox functionality, as a robust charge storage host for various charge carriers starting from hydronium ions, metal-ions to ammonium-ions. Owing to unusual redox charge storage in 1 M ammonium acetate (NH 4 OAc), BPA-CPP exhibits 5-fold superior charge storage capacity with remarkable cycling stability for more than 6000 cycles over the capacitive type of charge storage exhibited in the case of hydronium and hydrated metal ions. As a proof of concept, redox∥redox, redox∥capacitive type full-cell devices are also demonstrated based on BPA-CPP as a positive electrode, paired with the layered Ti 3 C 2 T x MXene as a negative electrode in different electrolytes, representing different charge storage mechanisms. This study provides avenues for developing conjugated porous polymers for sustainable ammonium-ion based energy storage devices.