Efficient Photocatalytic Synthesis of Hydrogen Peroxide Facilitated by Triptycene-Based 3D Covalent Organic...

Covalent organic frameworks (COFs) are widely studied for hydrogen peroxide (H₂O₂) photosynthesis, with 3D COFs standing out for their porous structures and chemical stability. However, the difficult preparation of 3D COFs and the low efficiency in separating photo-generated electrons and holes (e^- and h⁺) limits the efficient production of H₂O₂. In this study, two kinds of [6+3] 3D COFs (XJU-1, XJU-2) with significant charge separation, achieving record-breaking H₂O₂ photocatalysis rates of 34 777 and 11 922 µmol g⁻¹ h⁻¹, respectively. XJU-1's superior efficiency stems from its larger pores, enhancing material transport and oxygen (O₂) activation. Experimental and theoretical studies have demonstrated that triptycene monomers achieve significant charge separation toward triazine via imine bonds. Moreover, the dimer's smaller singlet-triplet energy gap (∆E_S-T) and triptycene's orthogonal configuration enhance singlet oxygen (¹O₂) production, enabling multiple H₂O₂ generation pathways. Ultimately, through the oxygen reduction reaction (ORR) pathway, rapid generation of H₂O₂ can be achieved at multiple catalytic sites. XJU-1 mainly follows a mixed pathway involving 1e^--ORR and 2e^--ORR, and XJU-2 primarily follows the 2e^--ORR pathway, respectively. These open the door of triptycene-based 3D COFs applied in continuous, efficient, and stable photosynthesis of H₂O₂.