Article pubs.acs.org/IECR
Cite This: Ind. Eng. Chem. Res. 2019, 58, 12835−12844
Hierarchically Porous and Water-Tolerant Metal−Organic Frameworks for Enzyme Encapsulation Yiying Sun,†,§ Jiafu Shi,*,‡,§ Shaohua Zhang,†,§ Yizhou Wu,†,§ Shuang Mei,†,§ Weilun Qian,† and Zhongyi Jiang†,§
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Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. China ‡ Tianjin Key Lab of Biomass/Wastes Utilization, School of Environmental Science & Engineering, Tianjin University, Tianjin 300072, P. R. China § Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, P. R. China S Supporting Information *
ABSTRACT: Metal−organic frameworks (MOFs) for in situ enzyme encapsulation commonly possess weak metal−ligand coordination bonds and rather small pores, which are instable in aqueous solution and present rather high diffusion resistance of reactants. Herein, we prepare a type of hierarchically porous and water-tolerant MOFs through a facile polyphenol treatment method for enzyme encapsulation. In brief, enzymes are first in situ encapsulated in a zeolitic imidazolate framework-8 (ZIF-8) through coprecipitation of enzymes, zinc ions (Zn2+), and 2-imidazole molecules (2-MI). Then, tannic acid (TA, a typical polyphenol) is introduced to functionalize the surface and etch the void of ZIF-8, acquiring the biocatalyst termed as E@ZIF8@ZnTA. The hierarchically porous structure would accelerate the diffusion process of reactants, whereas the Zn-O bond in a TA-Zn nanocoating would improve the structural stability against water corrosion compared to ZIF-8. Taking glucose oxidase (GOD) as a model enzyme for the catalytic conversion of β-D-glucose, the resultant GOD@ZIF-8@ZnTA exhibits the equilibrium conversion of 77.4%, which is comparable to GOD@ZIF-8 but much higher than GOD@ZIF-8@ZnTA without void etching. More importantly, the GOD@ZIF-8@ZnTA shows significantly enhanced recycling and storage stabilities compared to GOD@ZIF-8. It is expected that our study provides a facile and generic method to encapsulate a broad range of enzymes in MOFs with enhanced activity and stabilities.
1. INTRODUCTION Metal−organic frameworks (MOFs) are a class of porous materials based on coordination between metal nodes and organic ligands.1−5 The intrinsic properties of MOFs, such as high porosity/surface area, designable pore size, and adjustable metal nodes/organic ligands, make them superior candidates for diverse catalytic processes.6−8 Particularly, MOFs have gained numerous attention as the platform to encapsulate enzymes for expanding the application areas of enzyme catalysis.9−11 To our knowledge, a series of enzymes, including catalase, cytochrome c, horseradish peroxidase, etc., have been in situ encapsulated in MOFs.12−16 The micropores (normally
