O–Zn–N-Bonded and Zn Vacancy-Rich ZnO/ZIF-8@CoPc Heterojunction for Photocatalytic N ₂ Reduction

In this work, a novel ternary heterojunction consisting of Zn vacancy-rich zinc oxide (Zn 1– x O), a zeolitic imidazolate framework-8 (ZIF-8), and cobalt phthalocyanine (CoPc) was fabricated for photocatalytic N 2 fixation. The Zn 1– x O/ZIF-8 composite with bridged O–Zn–N bonding was synthesized via in situ growth of ZIF-8 on Zn 1– x O, and it possessed a large surface area favorable for N 2 adsorption. The incorporation of CoPc with dispersed Co–N 4 (II) sites enhanced light harvesting and N 2 activation. Zn vacancies and coupled type II/Z-scheme charge transfer pathways in the heterojunction accelerated the separation of photogenerated charge carriers. As a result, the optimized catalyst exhibited superior and stable photocatalytic N 2 reduction performance via an alternating pathway in water, with an NH 4 + production rate of 65.2 μmol g –1 h –1, which is 17.0 times higher than that of ZnO. This study develops a novel ZnO-based heterojunction that simultaneously optimizes multiple key factors for efficient photocatalytic N 2 fixation.