Charge-Distribution and Microenvironment Dual Regulation of Covalent Organic Frameworks for Enhancing Photocatalytic H2O2 and H2 Production.

Abstract

The proton-coupled electron transfer (PCET) process which related to charge-distribution and proton environment of photocatalysts play a key role in the photocatalytic activity. Nevertheless, there is short of systematic studies on the influences of photocatalytic PCET process by regarding the above two factors at the molecular level. Herein, a series of covalent organic framework (COFs) (Py-Bd COF, Py-Sa COF and Py-OH-Sa COF) were synthesized by co-controlling charge-distribution of skeletons and microenvironment of pores, and were used as photocatalysts for O2-to-H2O2 and H2O-to-H2 reaction. Particularly, the strong electron-withdrawing sulfone groups and strong electron-rich hydroxy groups in Py-OH-Sa COF boosted photo-generated charge separation, also triggered more hydrophilic pores, thus enabling efficient transfer of the photo-induced electrons and protons to catalytic sites. By the above dual regulation, Py-OH-Sa COF showed high photocatalytic H2O2 yield (4.78 mmol g-1 h-1) and H2 production (64.21 mmol g-1 h-1). Moreover, the Py-OH-Sa COF exhibits an extraordinary apparent quantum yield (AQY) of 6.52% and 8.25% at 380 nm for H2O2 and H2 production. This work develops an important strategy for precise regulating PECT by co-regulation of charge-distribution and microenvironment of photocatalyst to enhance catalytic activity, which also offers novel insights for the design anddevelopment of efficient photocatalysts.