Interaction between Single Metal Atoms and UiO-66 Framework Revealed by Low-Dose Imaging.

Liu, Boyang; Chen, Xiao; Huang, Ning; Liu, Shaoxiong; Shen, Boyuan; Wei, Fei; Wang, Tiefeng · Nano Lett · 2023

basic_science · Level V

Where this comes from

Abstract

Atomically dispersed metals encapsulated in metal-organic frameworks (MOFs) have attracted extensive attention in catalysis and energy fields. Amino groups were considered conducive to the formation of single atom catalysts (SACs) due to the strong metal-linker interactions. Here, atomic details of Pt<sub>1</sub>@UiO-66 and Pd<sub>1</sub>@UiO-66-NH<sub>2</sub> are revealed using low-dose integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM). Single Pt atoms locate on the benzene ring of <i>p</i>-benzenedicarboxylic acid (BDC) linkers in Pt@UiO-66, while single Pd atoms are adsorbed by the amino groups in Pd@UiO-66-NH<sub>2</sub>. However, Pt@UiO-66-NH<sub>2</sub> and Pd@UiO-66 show obvious clusters. Therefore, amino groups do not always favor the formation of SACs, and density functional theory (DFT) calculations indicate that a moderate binding strength between metals and MOFs is preferred. These results directly reveal the adsorption sites of single metal atoms in UiO-66 family, paving the way for understanding the interaction between single metal atoms and the MOFs.