Internal hydrogen-bond enhanced two-electron oxygen reduction reaction for π-d conjugated metal-organic framework to HO synthesis.

Tailoring the electronic structure of electrocatalysts for oxygen reduction reaction (ORR) has been widely adopted to optimize their performance. However, the steric effect originating from the layered or crystal structure of a catalyst is often neglected. Herein, we demonstrate the importance of such steric effect in a one-dimensional π-d conjugated metal-organic framework with Ni-(NH) nodes (Ni-BTA) for optimizing its electrocatalytic performance, where the activity and selectivity towards two-electron ORR for HO production are largely enhanced. Theoretical simulation and in-situ characterization demonstrate the formation of inter-layer H-bonds between *OOH intermediates and -N-H groups in the adjacent top layers of the Ni-sites, enhancing the *OOH binding energy to an optimum value. Thus, the as-prepared Ni-BTA catalyst exhibits an outstanding electrocatalytic 2e-ORR performances under neutral and alkaline conditions (e.g., >85% HO selectivity from -0.1-0.4 V vs. RHE and >13.5 mol g h HO yield in neutral electrolytes), also showing great potential on water treatment and disinfection. Here, we highlight the alternative avenues for utilizing the non-coordinated structure to regulate the catalytic performance, thus providing opportunities for the design of catalysts and beyond.