Influence of Different Solvents on the Structure of ZIF-67 for Enzyme Immobilization Matrices

Metal-organic framework (MOF) is a crystalline structure which has high porosity and surface area. MOFs’ design and functionality are versatile and stem from limitless combination of metals and organic linkers, which has proven stability in processes operated at high pH and temperature and resistant to various chemicals. These features are effective in biocatalysis as enzymes need protection from harsh environments. Nevertheless, during the synthesis of Enzyme-Metal organic complexes (E-MOF), the process must be designed in a delicate way such as avoiding harsh solvent (methanol) and room temperature synthesis, to preserve protein microenvironment. The study is aimed at analyzing the effect of different solvents; ultrapure water (which consists only H+ and OH- ions) and methanol towards ZIF-67 morphology. ZIF-67(W) shows leaf-like morphology with crystal size in the range of 10-16μm while ZIF-67(M) shows rhombic dodecahedron morphology with crystal size in the range of 200-400nm. It was found that ZIF-67(M) has better thermal stability compared to ZIF-67(W). The relationship between the different solvents used to synthesize ZIF-67 and in-situ enzyme encapsulation is discussed by considering the feasibility of ZIF-67 synthesis with water as an eco-friendly solvent with good characteristics. Preliminary result showed that more than 90% of methylene blue can be degraded by laccase@ZIF-67(W).