Predicting the Thermodynamic Limits of Metal-Organic Framework Metastability

The vast combinatorial space of metal-organic frameworks (MOFs) has led to their widespread consideration across diverse application areas. That said, much remains unknown about what factors govern their thermodynamic stability. Herein, we use density functional theory to compute the formation energy and construct convex hull phase diagrams for 20,000+ MOFs and coordination polymers. Using the energy above hull as a measure of stability with respect to decomposition and phase transitions, we validate and expand upon previous hypotheses that all MOFs are thermodynamically metastable and that there is an inherent energetic penalty associated with permanent porosity. We also describe how MOF composition and metal/linker identity influence the degree of metastability, in addition to demonstrating how the energy above hull can be used as a synthesizability metric for newly proposed MOFs. To democratize the knowledge gained from our study, we have released the QMOF-Thermo Database, which is the first database of energy above hull values for MOFs and coordination polymers. We conclude by using the QMOF-Thermo Database to benchmark the ability of pretrained machine learning interatomic potentials to predict the energy above hull of MOFs, and we identify opportunities to correct their performance.