Porous Materials as a Platform for Highly Uniform Single-Atom Catalysts: Tuning the Electronic Structure for the Low-Temperature Oxidation of Carbon Monoxide

Abstract

The selective oxidation of carbon monoxide (CO) remains a challenge in many research areas. Here we propose using porous hybrid organic–inorganic frameworks as tunable single-metal site catalysts which can be utilized for the oxidation reaction. Low-valent zinc ions were embedded on ZSM-5 zeolite and metal organic framework (MOF) supports to be used as nonprecious metal catalysts. Unlike the case with ionic compensation between the metal and zeolite, linker-functionalized MOFs exhibit a delocalized electron of the metal residing on both the organic linker and the metal atom. This electron delocalization plays a crucial role in the catalytic activity by assisting charge transfer of the metal site to break the O–O bond. By adding electron-donating groups to the linker, we found the activation energy to be dramatically decreased to ∼4 kcal/mol compared with 18 kcal/mol for the zeolite. This is essential for oxidation at low temperature. Moreover, the donating groups result in a more stable Zn active site on ...