Location determination of metal nanoparticles relative to a metal-organic framework

Yu-Zhen Chen,Takeyuki Uchida,Qiang Xu,Jiandang Liu,Bang-Jiao Ye,Xianchun Liu,Hai-Long Jiang,Bingchuan Gu

doi:10.1038/s41467-019-11449-6

Abstract

Metal nanoparticles (NPs) stabilized by metal-organic frameworks (MOFs) have been intensively studied in recent decades, while investigations on the location of guest metal NPs relative to host MOF particles remain challenging and very rare. In this work, we have developed several characterization techniques, including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography, hyperpolarized 129Xe NMR spectroscopy and positron annihilation spectroscopy (PAS), which are able to determine the specific location of metal NPs relative to the MOF particle. The fine PdCu NPs confined inside MIL-101 exhibit excellent catalytic activity, absolute selectivity and satisfied recyclability in the aerobic oxidation of benzyl alcohol in pure water. As far as we know, the determination for the location of metal NPs relative to MOF particles and pore structure information of metal NPs/MOF composites by 129Xe NMR and PAS techniques has not yet been reported.

Highlights

Metal nanoparticles (NPs) stabilized by metal-organic frameworks (MOFs) have been intensively studied in recent decades, while investigations on the location of guest metal NPs relative to host MOF particles remain challenging and very rare
The assertion for MNP location relative to MOF particles are mostly based on the sizes between MNPs and MOF pores, where smaller sizes of MNPs than MOF cavities are deemed to be embedded inside MOFs
Size-selective catalysis has been employed as an important evidence to distinguish whether or not MNPs are encapsulated into MOF pores: small substrate has high conversion while large substrate cannot be accessible to MNPs inside a MOF not be reacted[34,35,36]

Summary

Introduction

Metal nanoparticles (NPs) stabilized by metal-organic frameworks (MOFs) have been intensively studied in recent decades, while investigations on the location of guest metal NPs relative to host MOF particles remain challenging and very rare. As far as we know, the determination for the location of metal NPs relative to MOF particles and pore structure information of metal NPs/MOF composites by 129Xe NMR and PAS techniques has not yet been reported. The well-known size effect of metal nanoparticles (NPs) strongly affects their catalytic performance: small MNPs with large surface area are highly desirable. These small MNPs with high surface energies readily aggregate to form larger MNPs with deteriorated catalytic activity[15,16,17]. The nondestructive and auto detective property makes it an effective method to study metals, semiconductors, and other porous materials[60], PAS should be suitable to characterize the location of MNPs relative to MOF particle

Methods

Results

Conclusion