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1. Rapid mechanochemical encapsulation of biocatalysts into robust metal–organic frameworks

   https://doi.org/10.1038/s41467-019-12966-0  

   Wei, Tz-Han ; Wu, Shi-Hong ; Huang, Yi-Da ; Lo, Wei-Shang ; Williams, Benjamin P. ; Chen, Sheng-Yu ; Yang, Hsun-Chih ; Hsu, Yu-Shen ; Lin, Zih-Yin ; Chen, Xin-Hua ; et al ( November 2019 , Nature Communications)

   Metal–organic frameworks (MOFs) have recently garnered consideration as an attractive solid substrate because the highly tunable MOF framework can not only serve as an inert host but also enhance the selectivity, stability, and/or activity of the enzymes. Herein, we demonstrate the advantages of using a mechanochemical strategy to encapsulate enzymes into robust MOFs. A range of enzymes, namely β-glucosidase, invertase, β-galactosidase, and catalase, are encapsulated in ZIF-8, UiO-66-NH₂, or Zn-MOF-74 via a ball milling process. The solid-state mechanochemical strategy is rapid and minimizes the use of organic solvents and strong acids during synthesis, allowing the encapsulation of enzymes intomore »three prototypical robust MOFs while maintaining enzymatic biological activity. The activity of encapsulated enzyme is demonstrated and shows increased resistance to proteases, even under acidic conditions. This work represents a step toward the creation of a suite of biomolecule-in-MOF composites for application in a variety of industrial processes.

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2. Synopsis of Factors Affecting Hydrogen Storage in Biomass-Derived Activated Carbons

   https://doi.org/10.3390/su13041947  

   Sultana, Al Ibtida ; Saha, Nepu ; Reza, M. Toufiq ( February 2021 , Sustainability)

   Hydrogen (H2) is largely regarded as a potential cost-efficient clean fuel primarily due to its beneficial properties, such as its high energy content and sustainability. With the rising demand for H2 in the past decades and its favorable characteristics as an energy carrier, the escalating USA consumption of pure H2 can be projected to reach 63 million tons by 2050. Despite the tremendous potential of H2 generation and its widespread application, transportation and storage of H2 have remained the major challenges of a sustainable H2 economy. Various efforts have been undertaken by storing H2 in activated carbons, metal organic frameworksmore »(MOFs), covalent organic frameworks (COFs), etc. Recently, the literature has been stressing the need to develop biomass-based activated carbons as an effective H2 storage material, as these are inexpensive adsorbents with tunable chemical, mechanical, and morphological properties. This article reviews the current research trends and perspectives on the role of various properties of biomass-based activated carbons on its H2 uptake capacity. The critical aspects of the governing factors of H2 storage, namely, the surface morphology (specific surface area, pore volume, and pore size distribution), surface functionality (heteroatom and functional groups), physical condition of H2 storage (temperature and pressure), and thermodynamic properties (heat of adsorption and desorption), are discussed. A comprehensive survey of the literature showed that an “ideal” biomass-based activated carbon sorbent with a micropore size typically below 10 Å, micropore volume greater than 1.5 cm3/g, and high surface area of 4000 m2/g or more may help in substantial gravimetric H2 uptake of >10 wt% at cryogenic conditions (−196 °C), as smaller pores benefit by stronger physisorption due to the high heat of adsorption.« less
3. One-pot synthesis of enzyme@metal–organic material (MOM) biocomposites for enzyme biocatalysis

   https://doi.org/DOI https://doi.org/10.1039/D1GC00775K  

   Pan, Y. ; Li, H. ; Lenertz, M. ; Han, Y. ; Ugrinov, A. ; Kilin, D. ; Chen, B. ; Yang, Z. ( March 2021 , Green chemistry)

   Metal–organic frameworks/materials (MOFs/MOMs) are advanced enzyme immobilization platforms that improve biocatalysis, materials science, and protein biophysics. A unique way to immobilize enzymes is co-crystallization/co-precipitation, which removes the limitation on enzyme/substrate size. Thus far, most enzyme@MOF composites rely on the use of non-sustainable chemicals and, in certain cases, heavy metals, which not only creates concerns regarding environmental conservation but also limits their applications in nutrition and biomedicine. Here, we show that a dimeric compound derived from lignin, 5,5′-dehydrodivanillate (DDVA), co-precipitates with enzymes and low-toxicity metals, Ca2+ and Zn2+, and forms stable enzyme@Ca/Zn–MOM composites. We demonstrated this strategy on four enzymes withmore »different isoelectric points (IEPs), molecular weights, and substrate sizes. Furthermore, we found that all enzymes displayed slightly different but reasonable catalytic efficiencies upon immobilization in the Ca–DDVA and Zn–DDVA MOMs, as well as reasonable reusability in both composites. We then probed the structural basis of such differences using a representative enzyme and found enhanced restriction of enzymes in Zn–DDVA than in Ca–DDVA, which might have caused the activity difference. To the best of our knowledge, this is the first aqueous-phase, one-pot synthesis of a lignin-derived “green” enzyme@MOF/MOM platform that can host enzymes without any limitations on enzyme IEP, molecular weight, and substrate size. The different morphologies and crystallinities of the composites formed by Ca–DDVA and Zn–DDVA MOMs broaden their applications depending on the problem of interest. Our approach of enzyme immobilization not only improves the sustainability/reusability of almost all enzymes but also reduces/eliminates the use of non-sustainable resources. This synthesis method has a negligible environmental impact while the products are non-toxic to living things and the environment. The biocompatibility also makes it possible to carry out enzyme delivery/release for nutritional or biomedical applications via our “green” biocomposites.« less
4. Synthesis, Postsynthetic Modifications, and Applications of the First Quinoxaline-Based Covalent Organic Framework

   https://doi.org/https://doi.org/10.1021/acsami.1c08854  

   Valerie A. Kuehl, Phuoc H. ( January 2021 , ACS applied materials interfaces)

   We report a new synthetic protocol for preparing highly ordered two-dimensional nanoporous covalent organic frameworks (2D-COFs) based on a quinoxaline backbone. The quinoxaline framework represents a new type of COF that enables postsynthetic modification by placing two different chemical functionalities within the nanopores including layer-to-layer cross-linking. We also demonstrate that membranes fabricated using this new 2D-COF perform highly selective separations resulting in dramatic performance enhancement post cross-linking.
5. Nanozymes—Hitting the Biosensing “Target”

   https://doi.org/10.3390/s21155201  

   Wu, Yingfen ; Darland, Diane C. ; Zhao, Julia Xiaojun ( August 2021 , Sensors)

   Nanozymes are a class of artificial enzymes that have dimensions in the nanometer range and can be composed of simple metal and metal oxide nanoparticles, metal nanoclusters, dots (both quantum and carbon), nanotubes, nanowires, or multiple metal-organic frameworks (MOFs). They exhibit excellent catalytic activities with low cost, high operational robustness, and a stable shelf-life. More importantly, they are amenable to modifications that can change their surface structures and increase the range of their applications. There are three main classes of nanozymes including the peroxidase-like, the oxidase-like, and the antioxidant nanozymes. Each of these classes catalyzes a specific group of reactions.more »With the development of nanoscience and nanotechnology, the variety of applications for nanozymes in diverse fields has expanded dramatically, with the most popular applications in biosensing. Nanozyme-based novel biosensors have been designed to detect ions, small molecules, nucleic acids, proteins, and cancer cells. The current review focuses on the catalytic mechanism of nanozymes, their application in biosensing, and the identification of future directions for the field.« less