Ho‐Loaded ZIF‐L/COF Heterojunctions as Efficient Photocatalysts for H 2 O 2 Production

Covalent organic frameworks (COFs) exhibit considerable potential as photocatalysts for H 2 O 2 production through the oxygen reduction reaction (ORR) in water. However, their catalytic efficiency is often hindered by sluggish charge separation and a scarcity of sites for O 2 activation. Here, a heterojunction of Ho‐loaded ZIF‐L/triazine‐based COF (Ho‐ZIF‐L/TTA‐COF) is designed and synthesized through the electrostatically induced π–π assembly for efficient photocatalytic H 2 O 2 production. The optimized Ho‐ZIF‐L/TTA‐COF heterojunction achieves an impressive H 2 O 2 production rate of 7.19 mmol g −1 h −1 without any sacrificial agents under visible‐light irradiation, representing a 7.6‐fold enhancement compared to individual TTA‐COF. Based on the results of in situ X‐ray photoelectron spectroscopy and Kelvin probe force microscopy, the enhanced performance is mainly ascribed to the favorable electrons transfer from TTA‐COF to ZIF‐L then to the loaded Ho species for greatly enhancing charge separation. Noteworthily, Ho‐ZIF‐L possesses fully exposed Ho active sites and a large specific surface area, accounting for the efficient 2e − ORR dominated by the produced •O 2 − radicals for H 2 O 2 formation.