In the context of Schiff base metal complexes within these catalytic resins, the ion-exchange mechanism plays a crucial role in modulating the HER process . For Ni (II) bidentate Schiff base complexes, the ion-exchange resin facilitates the rapid delivery of protons to the nickel active sites, where they are adsorbed and subsequently reduced via electron transfer. The flexibility of the bidentate ligand allows for transient coordination changes, aiding the stabilization of reactive intermediates during hydrogen evolution. Conversely, Co (II) tetradentate Schiff base complexes benefit from the rigid coordination geometry, which stabilizes higher-valent cobalt intermediates and promotes efficient proton-coupled electron transfer (PCET). The ion-exchange matrix around the tetradentate complex ensures a steady proton supply while preventing catalyst deactivation through ligand dissociation or metal leaching. This interplay between ion-exchange dynamics and the electronic and geometric properties of the Schiff base complexes underpins the high efficiency and robustness of these systems in HER catalysis.