Cerium Oxide Nanoparticles Stabilized within Metal–Organic Frameworks for the Degradation of Nerve Agents

Abstract

Ceria nanoparticles (CeNPs) are promising enzyme mimetic catalysts due to their mixed oxidation states Ce3+/Ce4+ accompanied by the presence of oxygen vacancies. While their properties have been widely recognized, control of their activity, modulation of the Ce3+/Ce4+ ratio, dispersity, and accessibility of the active sites continue to be a challenge. Herein, we report a technique to synthesize highly active, ultrasmall CeNPs dispersed within a cerium-based metal–organic framework (Ce-MOF) via in situ etching of the parent NPs. Etching and stabilization of CeNPs within the MOF significantly enhanced their activity, prevented aggregation, and provided high accessibility of the active sites for catalytic reactions through the open channels of the MOF. The resulting material showed an enhancement in the degradation kinetics of the nerve agent simulant dimethyl p-nitrophenylphosphate (DMNP) as compared to the parent CeNPs or the Ce-MOF. These properties, characterized by a combination of optical imaging and spectroscopic techniques, are due to increased oxygen vacancies, an enhanced Ce3+ content at the surface, and the formation of ultrasmall CeNPs (∼1–2 nm) highly dispersed within the MOF matrix. This technique offers a strategy for controlling the surface chemistry of CeNPs, making them significantly more active for use in catalysis, sensing, and environmental remediation.