Coordination Engineering of Iron‐Polyphthalocyanines with H‐Substituted Graphdiyne for the Tandem Catalysis of Nitrate to Hydroxylamine

Abstract Hydroxylamine (NH 2 OH) can be generated by controlling the nitrate electroreduction process, the key of which lies in the hydrogenation of *NO. In this study, hydrogen‐substituted graphdiyne (HsGDY) is developed to engineer the growth of iron‐polyphthalocyanine (FePPc) with four Fe‐N 4 centers around the diacetylene linkages via d–π interactions, where numerous isolated electrochemical interfaces with high degrees of site exposure are achieved. Density functional theory results indicate electron transfer from Fe‐N 4 sites to diacetylene linkages, which prevents the hydrogenation of *NH 2 OH. In such a hybrid, a relay process occurs between HsGDY and FePPc, where the diacetylene linkages work as the transfer stations of NO 3 − to NO 2 − , whereas the isolated Fe‐N 4 sites further help manage NO 2 − to NH 2 OH. In addition, the well‐aligned nanoarrays along with the extended conjugated structure of HsGDY make it effective in directing both electron and mass transfer around FePPc. Thus, HsGDY@FePPc achieves a NH 2 OH yield rate of 52.3 µmol h −1 cm −2 with a Faradic efficiency (FE) of 34.0% at − 0.7 V vs RHE. When further applied in the electrosynthesis of cyclohexanone oxime, a FE of 51.0% is achieved. This work reports a coordination method for engineering both the structure and performance of a molecular catalyst via the diacetylene linkages of HsGDY.