Mesoporous Metal–Organic Framework with Well-Defined Cruciate Flower-Like Morphology for Enzyme Immobilization

Abstract

Metal-organic frameworks (MOFs) have recently emerged as a promising candidates for the immobilization of enzymes due to their diversified structures and porosity. However, a lack of good size and morphological control over the as-prepared MOFs has limited their practical applications in some cases. Herein, instead of zeolitic imidazolate framework-8 (ZIF-8) with the standard rhombic dodecahedral morphology, we successfully synthesize a novel mesoporous catalase@ZIF composite with cruciate flower-like morphology by embedding catalase molecules into uniformly sized ZIF crystals. With extraordinarily large mesopore size and high protein loading capacity, the catalase@ZIF composites with cruciate flower-like morphology exhibit 400% higher activity than that of catalase@ZIF composites with conventional rhombic dodecahedral morphology, and show higher reusability than conventional rhombic dodecahedral morphology. More importantly, we demonstrate for the first time that the biomacromolecules (proteins) can not directly regulate the crystal size, morphology, and crystallinity of ZIF-8. Moreover, the crystal morphology of ZIF has primary dependence on concentrations of 2-methylimidazole and Zn ions, and can be directly controlled by adjusting concentrations of Zn ions while keeping the high concentration of 2-methylimidazole.

X-Shaped ZIF-8 for Immobilization Rhizomucor miehei Lipase via Encapsulation and Its Application toward Biodiesel Production

“…Zif-8 encapsulated lipases were prepared according to a modified method [23]. Zn (NO3) 2 (0.148 g, 0.5 M) had been disbanding in 1 mL deionized (DI) water and dripped through a syringe into mixture solution of 25 mg of lipase and 2-methylimidazole (0.656 g, 0.8 M, 10 mL) under stirring at 200 rpm at 30 • C for 20 min.…”

Lipase Encapsulation onto ZIF‐8: A Comparison between Biocatalysts Obtained at Low and High Zinc/2‐Methylimidazole Molar Ratio in Aqueous Medium

“…Among these, water synthesis is facile, rapid, and low cost . Moreover, this is a very suitable way to obtain enzyme@ZIF conjugates . ZIF‐8 is a metal–organic framework where Zn 2+ ions are coordinated by 2‐methylimidazole (2‐MIM) to form rhombic dodecahedral structures .…”

“…These structures are often referred to as “SOD‐like” owing to their similarity to those of the natural zeolite “sodalite”. Although water synthesis is predominantly used for the immobilization of single enzymes or to obtain bienzymatic systems, some critical aspects of the mechanism of formation remain unknown. The mechanism of crystallization, porosity, and the surface area of pure ZIFs prepared in aqueous media are strongly influenced by the molar ratio between Zn 2+ ions and the alkyl‐imidazole ligand, as well as by the water content .…”

“…The mechanism of crystallization, porosity, and the surface area of pure ZIFs prepared in aqueous media are strongly influenced by the molar ratio between Zn 2+ ions and the alkyl‐imidazole ligand, as well as by the water content . Moreover, the addition of the enzyme to the reaction mixture during crystal nucleation can affect the crystal shape and morphology and, consequently, the activity of the obtained immobilized biocatalyst …”

Immobilization of laccase onto modified PU/RC nanofiber via atom transfer radical polymerization method and application in removal of bisphenol A

“…The characteristics of an ideal carrier for enzyme immobilization include inexpensive nature , being able to load a significant amount of enzyme per unit weight , low hydrophobicity , inertness after immobilization , microbial resistance , pH, thermal, and mechanical resistance . Conventionally, nanoparticles and microspheres have been used as carriers for immobilized enzymes because of their large specific surface area and porosity, resulting in higher enzyme loading of the immobilization process .…”