Trends in Siting of Metals in Heterometallic Nd-Yb Metal-Organic Frameworks and Molecular Crystals

Several studies suggest that metal ordering within metal-organic frameworks (MOFs) is important for understanding how MOFs behave in relevant applications; however, these siting trends can be difficult to determine experimentally. To garner insight into the energetic driving forces that may lead to nonrandom ordering within heterometallic MOFs, we employ density functional theory (DFT) calculations on several bimetallic metal-organic crystals composed of Nd and Yb metal atoms. We also investigate the metal siting trends for a newly synthesized MOF. Our DFT-based energy of mixing results suggest that Nd will likely occupy sites with greater access to electronegative atoms and that local homometallic domains within a mixed-metal Nd-Yb system are favored. We also explore the use of less computationally extensive methods such as classical force fields and cluster expansion models to understand their feasibility for large system sizes. This study highlights the impact of metal ordering on the energetic stability of heterometallic MOFs and crystal structures.

Automated summary

Several studies suggest that metal ordering within metal-organic frameworks (MOFs) is important for understanding the behavior of MOFs in applications. This study used density functional theory (DFT) calculations to investigate metal siting trends in bimetallic MOFs composed of Nd and Yb metal atoms. The results suggest that Nd tends to occupy sites with greater access to electronegative atoms, and local homometallic domains within a mixed-metal Nd-Yb system are favored. The study also explored the feasibility of using less computationally extensive methods for large system sizes.