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.

Defect-Rich La2O3 Nanoparticles with Antioxidant Activity for Human Keratinocytes

“…It has shown promising ROS scavenging properties due to its redox cycling between the Ce 3+ /Ce 4+ oxidation states. The redox efficiency of cerium depends upon the ratio of Ce 4+ and Ce 3+ ions and is controlled through oxygen deficiencies and defects in the structure. ,− The introduction of oxygen vacancies and other defects into nanostructures are vital to attain the desired oxidation states for achieving optimum catalytic antioxidant performance.…”

Globular pattern formation of hierarchical ceria nanoarchitecture

“…4) indicate non-negligible amounts of oxygen vacancies compared to those within CeO2 powder. [37][38][39] These trends are especially remarkable in the batches containing the primary clusters. Conversely, at the relatively high concentrations of 1.00 and 0.50 M, the Raman signals are more distinct than those in the spectra of the secondary clusters.…”

Recent Progresses in Metal–Organic Frameworks Based Core–shell Composites

“…[52] Metal oxide/ Metal(0) nanoparticles have also been used as sacrificing agents to form core-shell architectures. [53,54] For example, Che et al synthesized nanostructures of the octahedron and flower Pt-Cu@HKUST-1, where Pt-Cu alloys acted as a template for the subsequent MOF shell growth in-situ via the consumption of Cu(0). In a typical synthesis, Pt-Cu alloy with various morphologies were pre-synthesized (Figure 3D, schematic illustration) and PVP was used as capping agent for protecting active Pt-Cu alloy while Fe(III) was used in order to oxidize Cu(0) in Cu(II).…”

“…Core-shell structures can solve this issue by embedding the NPs within the MOF particles. Apart from the confinement of active particles in core-shell composites, remarkable synergetic effects led to promising catalytic performances (e.g., Ref 29,66,67,53) such as enhancement of the selectivity and/or conversion. Indeed, the in-situ growth of shell on the surface of the core objects allows a close packing between NPs and MOFs, which enables efficient energy/charge transfer between the MOF and the active NPs, similar to Schottky junctions observed in the metal-semiconductor materials.…”