Interaction between Single Metal Atoms and UiO-66 Framework Revealed by Low-Dose Imaging
Boyang Liu, Xiao Chen, Ning Huang, Shaoxiong Liu, Boyuan Shen, Fei Wei, Tiefeng Wang
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 1 @UiO-66 and Pd 1 @UiO-66-NH 2 are revealed using low-dose integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM). Single Pt atoms locate on the benzene ring of p -benzenedicarboxylic acid (BDC) linkers in Pt@UiO-66, while single Pd atoms are adsorbed by the amino groups in Pd@UiO-66-NH 2 . However, Pt@UiO-66-NH 2 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.