Nanometric Metal−Organic Framework of Ln[Fe(CN)6]: Morphological Analysis and Thermal Conversion Dynamics by Direct TEM Observation

Abstract

Metal−organic frameworks (MOFs) can possess various crystal structures due to the combination of metal ions and organic bridging ligands, resulting in versatile electronic and optical characteristics. The architecture of nanometer-sized MOFs is one of the prime areas of study in producing novel nanomaterials. However, the methodology is still in progress, as relevant research reports remain scarce. In this Article, we report the synthesis of cyano bridged MOFs comprising iron and lanthanide ions (Fe−CN−Ln, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), generally formulated as Ln[Fe(CN)6] in a water/alcohol dilute solution system containing acetic acid as an additive. Specific morphologies of Fe−CN−Ln such as hexagons, asterisks, and rods with a size of approximately 200−600 nm were observed depending on the particular Ln ions introduced. Specifically, the formation mechanism of nanoasterisks of Fe−CN−Sm was precisely investigated by high-resolution transmission microscopy (HRTEM), which rev...