Fast Photocatalytic Hydrogen Peroxide Generation by Singlet Oxygen-Engaged Sequential Excitation Energy and Electron-Transfer Process

Abstract

Sequential excitation energy and electron transfer (ET) are ubiquitous pathways for converting solar energy to chemical energy in photosynthesis. Mimicking this unique process for chemical synthesis is promising yet still a big challenge. Herein, taking photosynthesis as an inspiration, we demonstrate an interesting pathway for oxygen reduction to hydrogen peroxide (H2O2), an important and valuable commodity chemical. The proposed route was verified on a biomimetic photocatalyst, i.e., an aluminum porphyrin metal-organic framework nanosheet (Al-TCPP). Experimental investigations and theoretical calculations reveal that the dioxygen molecule is first converted to a highly active singlet oxygen intermediate through an excitation energy transfer (EET) and then reduced to H2O2 via the photogenerated electrons with a reduced barrier over Al-TCPP. Consequently, Al-TCPP shows a 32 times higher H2O2 evolution rate than that of the pristine TCPP counterpart, wherein excitation energy transfer mainly exists. This study presents a paradigm to mimic the photosynthetic sequential excitation energy and electron-transfer process for improved synthesis of valuable commodity chemicals.