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 (Zn 2+ ), 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@ZIF-8@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

Design and preparation of high-performance immobilized biocatalysts with exquisite structures and elucidation of their profound structure-performance relationship are highly desired for green and sustainable biotransformation processes. Learning from nature has been recognized as a shortcut to achieve such an impressive goal. Loose connective tissue, which is composed of hierarchically organized cells by extracellular matrix (ECM) and is recognized as an efficient catalytic system to ensure the ordered proceeding of metabolism, may offer an ideal prototype for preparing immobilized biocatalysts with high catalytic activity, recyclability, and stability. Inspired by the hierarchical structure of loose connective tissue, we prepared an immobilized biocatalyst enabled by microcapsules-in-hydrogel (MCH) scaffolds via biomimetic mineralization in agarose hydrogel. In brief, the in situ synthesized hybrid microcapsules encapsulated with glucose oxidase (GOD) are hierarchically organized by the fibrous framework of agarose hydrogel, where the fibers are intercalated into the capsule wall. The as-prepared immobilized biocatalyst shows structure-dependent catalytic performance. The porous hydrogel permits free diffusion of glucose molecules (diffusion coefficient: ∼6 × 10(-6) cm(2) s(-1), close to that in water) and retains the enzyme activity as much as possible after immobilization (initial reaction rate: 1.5 × 10(-2) mM min(-1)). The monolithic macroscale of agarose hydrogel facilitates the easy recycling of the immobilized biocatalyst (only by using tweezers), which contributes to the nonactivity decline during the recycling test. The fiber-intercalating structure elevates the mechanical stability of the in situ synthesized hybrid microcapsules, which inhibits the leaching and enhances the stability of the encapsulated GOD, achieving immobilization efficiency of ∼95%. This study will, therefore, provide a generic method for the hierarchical organization of (bio)active materials and the rational design of novel (bio)catalysts.

Herein, a facile and generic method is developed to prepare ultrathin, robust nanohybrid capsules by manipulating the dynamic structure of supramolecular nanocoatings on CaCO sacrificial templates by incorporating a multivalent-anion substitution process into biomineralization. Above the biomineralization level, multivalent anions, for example, phosphate, sulfate, or citrate, are used to initiate the assembly of polyamine into continuous (nonsegregated) polyamine-anion supramolecular nanocoatings on CaCO sacrificial templates. When contacting with the sodium silicate solution, the multivalent anions in the supramolecular nanocoatings are substituted by silicate because of the difference in dissociation behavior, facilitating the structure-reconstruction of supramolecular nanocoatings. At the biomineralization level, the substituted silicate can not only bind to the polyamine through electrostatic and hydrogen bonding interactions but also undergo silicification to generate an interpenetrating silica framework. After dissolution of CaCO, polyamine-silica nanohybrid capsules bearing an ultrathin wall of ∼10-17 nm in thickness are formed, which exhibit a super-high mechanical strength of ∼2337 MPa in elasticity modulus. The capsules are then utilized for bioreactor construction by encapsulating glucose oxidase. The ultrathin capsule wall facilitates the diffusion of substrates/products and elevates the conversion efficiency, whereas the high mechanical strength ensures the structural integrity of the capsules during multiple-cycle reactions. This method can also be applied for the preparation of ultrathin films on planar substrates, which would open a feasible way to prepare nanohybrid materials with different compositions and shapes.

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