Ordered Macro–Microporous ZIF-8 with Different Macropore Sizes and Their Stable Derivatives for Lipase Immobilization in Biodiesel Production

Abstract

Enzyme immobilization in hierarchical macro–microporous metal–organic frameworks (MOFs) is greatly desirable but challenging due to the poor stability of MOFs in a practical biocatalysis process. Herein, we prepared a series of single-crystalline ordered macro–microporous zeolitic imidazolate framework-8 (SOM-ZIF-8) with different macropore sizes of 180, 270, and 360 nm for lipase immobilization and investigated their performance in a practical biodiesel production process. Under an ethanol-assisted infiltration strategy, the potential of SOM-ZIF-8 for enzyme immobilization was unleashed from the nonwettability arising from its exceptional surface hydrophobicity, with a significant increase by 123.8% in the loading capacity. However, a fatty acid-induced complete decomposition of ZIF-8 in a nonaqueous system of biodiesel production was observed. To address this challenge, a degradation mechanism coupling the intermolecular autoionization of carboxylic acid was proposed, and a template-assisted pyrolysis approach was adopted to prepare the SOM-ZIF-8-derived carbon material that not only well preserved the 3D-ordered structure of the precursor but also exhibited enhanced chemical stability. Moreover, the carbon derivative exhibited great potential for enzyme immobilization, with a 22.9% increase in loading capacity, a 35.9% increase in specific activity, and a 12.7% increase in activity recovery, compared with SOM-ZIF-8. It is anticipated that this study will shed new light on the realistic design and modification of MOFs for the immobilization of enzymes in biocatalysis and extensive applications.

Synthesis of l-aspartic acid-based bimetallic hybrid nanoflowers to immobilize snailase for the production of rare ginsenoside compound K

“…Zeolitic imidazoles (ZIFs) are common materials for immobilizing enzymes because of their simple synthesis, high specific surface area, and good biocompatibility. 6 Cheng et al 7 prepared a nanoscale MAC-ZIF-8-based immobilized nanolipase with a hierarchical microporous structure, which was almost eight times more active than the free lipase. Pei et al 8 encapsulated recombinant cobalt-based nitrile hydrolases by biomimetic mineralization in ZIF-67-containing mesoporous ZIF-67, which has good stability; thus, it is a potential nanocatalyst for the large-scale industrial preparation of nicotinamide.…”

“…Zeolitic imidazoles (ZIFs) are common materials for immobilizing enzymes because of their simple synthesis, high specific surface area, and good biocompatibility. 6 Cheng et al 7 prepared a nanoscale MAC-ZIF-8-based immobilized nanolipase with a hierarchical microporous structure, which was almost eight times more active than the free lipase. Pei et al 8…”

Enhanced Stability and Performance of Immobilized Lipase Using Hydrophobically Modified Single-Crystalline Ordered Macro–Microporous CuBTC as a Carrier Material

“…Moreover, the selection of ligands with hydrophobic units and postsynthesis hydrophobic modification are effective strategies to improve the water stability of MOFs. , In nonaqueous systems, the tolerability of MOF to long-chain fatty acids also deserves attention, as fatty acids are a common component in lipase-catalyzed reactions and have been reported to pose a risk of damaging the structure of MOFs . For example, ZIF-8, which was previously considered an inert carrier in lipase immobilization due to its good chemical stability, was found to undergo irreversible structural breakdown in the presence of fatty acids, as reported by Zhou et al This breakdown was thought to be induced by the stronger affinity of the azole linkage with a proton released by the ionization of fatty acids compared to a metal ion. Generally, the p K a of carboxylate-based ligands is lower than that of azolate ligands, suggesting that they are more difficult to bind to protons released by the ionization of fatty acids.…”

Optimizing the Green Synthesis of ZIF-8 by Reactive Extrusion Using In Situ Raman Spectroscopy

“…6 ZIF-8 or Zn(meIm) 2 (meIm = deprotonated 2-methylimidazole) is a prototypical member of the zeolitic imidazolate framework (ZIF) subfamily of MOFs, which stands out due to its high porous properties compared to zeolites and exceptional thermal, chemical, and mechanical stability compared to other MOFs. 7,8 Due to various potential applications (e.g., in drug delivery, 9 wastewater treatment, 10 biodiesel production, 11 or hydrogen storage), 12 large quantities of ZIF-8 may be needed, which is why numerous synthetic routes have been explored so far (Figure 1). 13 Chen et al were the first to synthesize ZIF-8 in 2006 by a liquid-phase diffusion method.…”