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

ABSTRACT

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.