Defect metal-organic frameworks (D-MOFs): An engineered nanomaterial for enzyme immobilization

The field of metal-organic frameworks (MOFs) for enzyme immobilization has gained significant traction due to their versatile structural properties and exceptional stability. There are certain constraints after enzyme-MOF composite formation, such as (i) reduction in enzyme activity , (ii) mass transfer limitation between substrate-enzyme, and (iii) unfavorable micro-environment for immobilized enzyme within MOF. Therefore, the defects in MOFs have emerged as a powerful tool to enhance the enzyme catalytic properties and their loading. This review delves into the recent advancements in defect engineering of MOFs, elucidating the role of structural defects in creating mesoporous environments that facilitate superior enzyme immobilization and activity. The synthesis strategies, such as post-synthetic and de-novo methods for controlled defect formation, are comprehensively discussed. Moreover, the integration of machine learning approaches for predicting and optimizing D-MOFs is highlighted, showcasing their transformative impact on biocatalytic applications. The challenges related to synthesis, characterization, enzyme microenvironment, separation, and recycling are critically examined, focusing on the future scope of defect MOFs in sustainable and scalable biocatalysis. This review underscores the untapped potential of defect engineering in MOFs to revolutionize enzyme immobilization, paving the way for innovative biocatalytic processes and applications. The defect-rich metal-organic frameworks coupled with enzymes significantly enhance the catalytic properties in terms of activity and stability. • The defect MOF can be synthesized by de novo and post-treatment synthetic methodologies. • The defect MOF-enzyme composite exhibits superior catalytic activity and conformational stability. • The defect MOF provides a carrier matrix and improves mass transfer between enzyme-substrate. • Understanding defective MOFs will open fresh discoveries that extend MOF applications.