Assessing Structural, Thermal, and Mechanical Properties of Zirconium-Based Metal-Organic Frameworks via DFTB3/3OB MD Simulations: A Benchmark Beyond UiO Frameworks

The exceptional stability and broad application potential of zirconium-based metal-organic frameworks call for reliable atomistic methods capable of describing their structural, thermal, and mechanical properties. In this work, we benchmark the recently introduced extension of the DFTB3/3OB parameter set for the transition metal zirconium by evaluating a representative set of Zr-containing metal-organic frameworks spanning different secondary building units and topologies, namely UiO-66, UiO-67, MOF-801, MIL-140A, and MIL-163. Equilibrium lattice parameters, X-ray diffraction patterns, thermal expansion coefficients, and volumetric stiffness measures have been computed from DFTB3/3OB molecular dynamics simulations and compared to literature reference data. The results have been further assessed using hybrid DFT (HSEsol) reference calculations and contextualized through an independent comparison with neural-network-based MACE-DAC-1 simulations. Across the benchmark set, DFTB3/3OB provides a consistent structural description and reproduces the dominant experimental diffraction features, while the deviations of the lattice parameters remain small. DFTB3/3OB correctly reproduces the negative thermal expansion behavior of the UiO frameworks and predicts positive thermal expansion for MOF-801; for the investigated MIL-type systems, the observed anisotropic expansion highlights a stronger method dependence. For the cubic frameworks UiO-66 and UiO-67, the bulk moduli obtained via DFTB3/3OB fall within reported reference ranges and generally indicate intermediate stiffness relative to MACE-DAC-1 and HSEsol. For the non-cubic MIL-140A and MIL-163, the corresponding MD-derived fixed-shape isotropic volumetric moduli provide a consistent basis for comparison between DFTB3/3OB and MACE-DAC-1. Overall, the presented results support the applicability and transferability of DFTB3/3OB to molecular dynamics simulations of zirconium-based MOFs beyond the prototypical UiO frameworks.