Protein-metal-organic frameworks (p-MOFs) offer a diverse platform for immobilization of biomolecules to enhance their stability and enzymatic activity. In a process analogous to biomineralization, biomolecules can induce the crystallization of p-MOF structures. However, the nucleation and growth mechanisms of these biomimetic crystallizations have not been well investigated. By gaining a better understanding of the parameters that govern nucleation and growth of MOF systems, their properties can be tuned for various applications such as encapsulation of biomolecules and sensing capabilities. Herein we studied the formation of a model zeolitic imidazole framework (ZIF-8) and the factors that lead to the formation of different polymorphs such as ligand to metal ratio, the introduction of a biomolecule, and solution pH. To understand the mechanism and factors that affect ZIF-8 polymorph formation, studies were performed using time resolved in-situ small and wide X-ray scattering (SAXS/WAXS), cryo-electron microscopy, micro-electron diffraction (microED) and electrospray ionization MS (ESI-MS). These data allow us to determine the influence of prenucleation clusters on final polymorph formation. Understanding polymorph control in p-MOF systems will lead to a better understanding of the structure function relationship and tighter control in the development of new MOFs.

Polymorph control in protein-metal-organic framework

ACS Spring 2022

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