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Protein-Metal-Organic Frameworks (MOFs) present a diverse array of building blocks for designing high-performance materials with applications spanning numerous industries including drug delivery, catalysis, and gas storage. However, the intricate crystallization mechanisms involving various pathways and intermediates complicate their understanding, stalling the implementation of the materials. Fundamental crystallization studies have been pivotal in advancing both biological and synthetic systems, and MOFs are no exception. This dissertation delves into how proteins exert control over the nucleation and growth of MOFs, influencing final crystal properties such as topology, morphology, and encapsulation efficiency. Advanced microscopy and scattering techniques, such as cryogenic transmission electron microscopy (cryoTEM) and powder x-ray diffraction (PXRD), are employed to conduct these studies. The investigation commences with zeolitic imidazolate framework-8 (ZIF-8) as a model MOF system and bovine serum albumin (BSA) as a model protein. Synthetic protocols are established to explore the impact of BSA concentration and ligand-to-metal ratios on ZIF-8 formation. Notably, the use of cryoTEM allows for the direct observation of MOFs, uncovering the role of transient amorphous phases in ZIF-8 nucleation and growth. Furthermore, in a follow up study, it was discovered how protein folding influences the stability of these amorphous phases, enabling modulation of key physical properties such as crystal size, morphology, and encapsulation efficiency. Moving beyond BSA, subsequent investigations aim to connect nucleation and growth mechanisms to the final enzymatic performance of MOFs using catalytically active proteins, namely glucose oxidase (GOx) and catalase (CAT). The results underscore the significance of protein folding in the initial complexes with MOF precursors, pivotal in designing active materials. To further tailor the extent of enzyme activity, the accessibility of the enzyme to substrates and its diffusion barrier can be controlled through final crystal properties, including size, topology, defects, and porosity. Generalizing these findings, the dissertation introduces two novel, catalytically active proteins into ZIF-8 for the first time, main protease (Mpro) of SARS-CoV-2 and Nanoluciferase (NanoLuc). In summary, this work provides valuable insights into how protein folding influences MOF nucleation and growth mechanisms and, consequently, their final crystal properties. The research contributes to the broader understanding of MOFs as versatile materials and paves the way for high-performance hybrid materials.