3D-Printed COF/Zeolite Composites for Augmented Photocatalytic Hydrogen Peroxide Production

Covalent organic frameworks (COFs), characterized by high porosity and fine-tuned structures, are promising photocatalysts for hydrogen peroxide (H₂O₂) production. However, their hydrophobic nature restricts the mass transfer in water, presenting challenges in achieving high performance. Coupling COFs with hydrophilic zeolites can potentially advance H₂O₂ production, yet integrating these two distinct types of porous materials is challenging. Herein, we first applied 3D printing technology to fabricate COF/zeolite composite catalysts, which enabled superior photosynthesis of H₂O₂. By precisely optimizing binders and prepolymerization conditions, homogeneous inks composed of zeolite nanocrystals and initial polymeric precursors were prepared with appropriate rheology for 3D printing. The resultant monolith with honeycomb-like open-channels was favorable for the in-situ growth and crystallization of COF by facilitating the efficient molecular transfer of condensing agents and large covalent segments during solvothermal post-treatment. Mechanistic studies indicated that introducing zeolites enhanced the hydrophilicity and O₂ affinity within the composite, favoring the oxygen reduction reaction pathway. Consequently, the photosynthesis of H₂O₂ by the COF/zeolite composite was markedly improved by 52% compared to the bare COFs. This work provides a facile way to integrate COFs and zeolites by 3D printing, which may open diverse applications of such composites by taking advantage of both merits.