## 3 Metal-Organic Frameworks
### MOFs by Bionic Mineralization  
Unlike the method involving the addition of co-precipitation agents, the biomimetic mineralization method involves the direct mixing of biomacromolecules with the organic ligands of MOFs. In this process, biomacromolecules act as the basic building blocks of MOFs, aiding in the nucleation of porous crystals and resulting in rapid crystallization around enzyme molecules. Hydrogen bonding and hydrophobic interactions between the organic ligands and enzyme molecules contribute to retaining the enzyme molecules within the MOF. The biomimetic mineralization method makes it possible for biomacromolecules to be fixed in situ during the synthesis process. This method does not require the addition of co-precipitation agents [108; 119], and its preparation conditions are mild, making the process economically efficient. Enzymes are uniformly distributed throughout the entire MOF crystal [120]. As it avoids the use of co-precipitation agents, the biomimetic mineralization method for preparing enzyme-MOF biohybrids eliminates the risk of co-precipitation agents damaging enzymes at high temperatures. Therefore, materials prepared through biomineralization exhibit enhanced stability over a broader temperature range [107; 121]. [PERSON] et al. reported the first example of biomimetic mineralization of MOFs by mixing a zinc acetate solution with a solution containing mIM and enzymes at room temperature, resulting in a ZIF-8-based biohybrid material. This method demonstrated that PVP and alcohol were not necessary. Similar to co-precipitation, this process encapsulates the target biomolecules and preserves their biological activity by imparting high biotic, thermal, and chemical stability. Moreover, this method can be applied to other MOFs (HKUST-1, Eu/Tb-BDC, and MIL-88A), highlighting the versatility of this biomimetic mineralization approach [106]. [PERSON] et al. prepared Lipase@Bio-MOF by mixing zinc acetate, adenine (an organic ligand), and enzymes in an aqueous solution [122]. Lipase@Bio-MOF exhibited good catalytic activity and stability under high temperatures, alkaline conditions, and in the presence of metal ions. Additionally, it demonstrated excellent recyclability in the biodiesel production process, with no changes in morphology or crystal structure after three cycles. Furthermore, [PERSON] et al. utilized the biomimetic mineralization method to prepare Laccase@HKUST-1 biohybrids [123]. In terms of the catalytic efficiency, \(\mathrm{K_{cat}/K_{m}}\) for laccase@HKUST-1 improved by nearly four times that for the laccase. Research by [PERSON] et al. indicated that the surface charge and chemical properties of proteins determine their ability to grow MOFs. Converting the basic residues on the protein surface into acidic or non-ionizable parts under standard conditions is a convenient strategy for promoting protein biomimetic mineralization [119]. The biomimetic mineralization process for preparing MOFs typically involves directly adding enzyme solutions to the encapsulation system. During this process, enzymes are usually stored in a solution containing various small molecules (such as NaCl, Tris, etc. ), and these small molecules may impact the rate and morphology of MOF formation [124]. [PERSON] and his team reported a method to prepare (\(R\))-PEDH@ZIF-8 by mixing ultrasonically activated (\(R\))-1-phenylethylal dehydrogenase ((\(R\))-PEDH), zinc nitrate, mIM, and NaCl. They investigated the influence of NaCl on the preparation of enzyme-MOF and its catalytic performance. The \(\mathrm{k_{cat}/K_{m}}\) of the (\(R\))-PEDH@ZIF-8 to (\(R\))-1-phenylethylal was 1935 mM\(\cdot\)s\({}^{-1}\), while the \(\mathrm{k_{cat}/K_{m}}\) of the free (\(R\))-PEDH was 158 mM\(\cdot\)s\({}^{-1}\), indicating that the (\(R\))-PEDH@ZIF-8 (prepared with 0.1 M NaCl) has better substrate affinity than the free (\(R\))-PEDH [125]. Mechanochemical processes, proven to be environmentally friendly alternatives to traditional solution-based processes, have been employed in the preparation of various MOFs [126].