Remarkably Enhancing H₂O₂ Photogeneration by Modulating Pore-Microenvironment of a Photoactive Covalent Organic Framework.

Abstract

While research mainly focuses on enhancing photoelectric properties to improve photocatalytic efficiency, the influence of mass transfer has not yet been taken seriously. Herein, the pore microenvironment of an imidazole-linked photoactive covalent organic framework (COF), PyNTB-COF, is modulated by uniformly grafting sulfonates to study the influence of increasing the mass transfer capability on photocatalytic H₂O₂ generation. Experimental studies reveal that the sulfonated PyNTB-2SO₃ exhibits a remarkable H₂O₂ production rate of 15158 µmol g^-1 h^-1 in the presence of a sacrificial agent, which is 20.6 times higher than that of the pristine COF. Further investigations reveal that its remarkable increase in photocatalytic efficiency of sulfonated PyNTB-2SO₃ should be attributed to the enhanced mass transfer kinetics of reactants (e.g., ·O₂ ^- H₂O, H⁺) and products after modulating the pore microenvironment. Moreover, the introduced sulfonic acids can also simultaneously improve the intrinsic charge distribution of the framework and enhance the electron-hole separation and transfer capability. In outdoor water samples, the photocatalytic antimicrobial activity of PyNTB-2SO₃ achieves >99% bacterial inactivation within 15 min, whereas the pristine PyNTB-COF requires ≈6 h. This finding demonstrates that modulating the pore microenvironment to enhance mass transfer is a promising strategy for developing high-performance photocatalysts for practical applications.