Computational Investigation of Molecular Stabilization Mechanisms of in-plane fractal patterns in two-dimensional Organic Frameworks*

Metal Organic Frameworks (MOFs) have emerged as important candidates for a diverse set of chemical applications such as catalysis and ion conduction. With sophisticated synthesis, MOFs can be structured into 2D configurations to create unique materials with intriguing properties. In this study, we detail the molecular mechanisms underpinning the etching of a 2D-MOF5 nanocrystal. Using Molecular Dynamics (MD) and Density Functional Theory (DFT), we investigate a crystal lattice-guided wet-chemical etching of a 2D MOF-5 nanocrystal, which resulted in two distinct anisotropic pore patterns: plus(+)-shaped and fractal-patterned pores via <100> and <110> directional etching, respectively. We identify two-step mechanism - the exchange of metal-coordinating solvent molecule with EtOH, and then the dissolution of EtOH-bound Zn-nodes. The thermodynamically preferred pathway proceeded through dissociation of Zn node in <100>-direction, while slow-diffusion limited kinetic pathway was induced by faster solvent exchange in <110>-direction. Based on this mechanism, the etching process has been optimized to yield superb catalytic activity with long-term stability, offering strategies for the creation of custom patterns on 2D nanomaterials to address new scientific challenges.