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Creators/Authors contains: "Ma, Kaikai"

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  1. Abstract

    Metal–organic frameworks (MOFs) with Lewis acid catalytic sites, such as zirconium‐based MOFs (Zr‐MOFs), comprise a growing class of phosphatase‐like nanozymes that can degrade toxic organophosphate pesticides and nerve agents. Rationally engineering and shaping MOFs from as‐synthesized powders into hierarchically porous monoliths is essential for their use in emerging applications, such as filters for air and water purification and personal protection gear. However, several challenges still limit the production of practical MOF composites, including the need for sophisticated reaction conditions, low MOF catalyst loadings in the resulting composites, and poor accessibility to MOF‐based active sites. To overcome these limitations, a rapid synthesis method is developed to introduce Zr‐MOF nanozyme coating into cellulose nanofibers, resulting in the formation of processable monolithic aerogel composites with high MOF loadings. These composites contain Zr‐MOF nanozymes embedded in the structure, and hierarchical macro‐micro porosity enables excellent accessibility to catalytic active sites. This multifaceted rational design strategy, including the selection of a MOF with many catalytic sites, fine‐tuning the coating morphology, and the fabrication of a hierarchically structured monolithic aerogel, renders synergistic effects toward the efficient continuous hydrolytic detoxification of organophosphorus‐based nerve agent simulants and pesticides from contaminated water.

     
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  2. Abstract

    Proteins immobilized in metal–organic frameworks (MOFs) often show extraordinary stability. However, most efforts to immobilize proteins in MOFs have only been exploratory. Herein, we present the first systematic study on the thermodynamics of protein immobilization in MOFs. Using insulin as a probe, we leveraged isothermal titration calorimetry (ITC) to investigate how topology, pore size, and hydrophobicity of MOFs influence immobilization. ITC data obtained from the encapsulation of insulin in a series of Zr‐MOFs reveals that MOFs provide proteins with a hydrophobic stabilizing microenvironment, making the encapsulation entropically driven. In particular, the pyrene‐based NU‐1000 tightly encapsulates insulin in its ideally sized mesopores and stabilizes insulin through π‐π stacking interactions, resulting in the most enthalpically favored encapsulation process among this series. This study reveals critical insights into the structure–property relationships of protein immobilization.

     
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  3. Abstract

    Proteins immobilized in metal–organic frameworks (MOFs) often show extraordinary stability. However, most efforts to immobilize proteins in MOFs have only been exploratory. Herein, we present the first systematic study on the thermodynamics of protein immobilization in MOFs. Using insulin as a probe, we leveraged isothermal titration calorimetry (ITC) to investigate how topology, pore size, and hydrophobicity of MOFs influence immobilization. ITC data obtained from the encapsulation of insulin in a series of Zr‐MOFs reveals that MOFs provide proteins with a hydrophobic stabilizing microenvironment, making the encapsulation entropically driven. In particular, the pyrene‐based NU‐1000 tightly encapsulates insulin in its ideally sized mesopores and stabilizes insulin through π‐π stacking interactions, resulting in the most enthalpically favored encapsulation process among this series. This study reveals critical insights into the structure–property relationships of protein immobilization.

     
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  4. Abstract

    The fabrication of MOF polymer composite materials enables the practical applications of MOF‐based technology, in particular for protective suits and masks. However, traditional production methods typically require organic solvent for processing which leads to environmental pollution, low‐loading efficiency, poor accessibility, and loss of functionality due to poor solvent resistance properties. For the first time, we have developed a microbial synthesis strategy to prepare a MOF/bacterial cellulose nanofiber composite sponge. The prepared sponge exhibited a hierarchically porous structure, high MOF loading (up to ≈90 %), good solvent resistance, and high catalytic activity for the liquid‐ and solid‐state hydrolysis of nerve agent simulants. Moreover, the MOF/ bacterial cellulose composite sponge reported here showed a nearly 8‐fold enhancement in the protection against an ultra‐toxic nerve agent (GD) in permeability studies as compared to a commercialized adsorptive carbon cloth. The results shown here present an essential step toward the practical application of MOF‐based protective gear against nerve agents.

     
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  5. Abstract

    The fabrication of MOF polymer composite materials enables the practical applications of MOF‐based technology, in particular for protective suits and masks. However, traditional production methods typically require organic solvent for processing which leads to environmental pollution, low‐loading efficiency, poor accessibility, and loss of functionality due to poor solvent resistance properties. For the first time, we have developed a microbial synthesis strategy to prepare a MOF/bacterial cellulose nanofiber composite sponge. The prepared sponge exhibited a hierarchically porous structure, high MOF loading (up to ≈90 %), good solvent resistance, and high catalytic activity for the liquid‐ and solid‐state hydrolysis of nerve agent simulants. Moreover, the MOF/ bacterial cellulose composite sponge reported here showed a nearly 8‐fold enhancement in the protection against an ultra‐toxic nerve agent (GD) in permeability studies as compared to a commercialized adsorptive carbon cloth. The results shown here present an essential step toward the practical application of MOF‐based protective gear against nerve agents.

     
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  6. Abstract

    Polyethylene terephthalate (PET) is utilized as one of the most popular consumer plastics worldwide, but difficulties associated with recycling PET have generated a severe environmental crisis with most PET ending its lifecycle in landfills. We report that zirconium‐based metal–organic framework (Zr‐MOF) UiO‐66 deconstructs waste PET into the building blocks terephthalic acid (TA) and mono‐methyl terephthalate (MMT) within 24 hours at 260 °C (total yield of 98 % under 1 atm H2and 81 % under 1 atm Ar). Extensive structural characterization studies reveal that during the degradation process, UiO‐66 undergoes an intriguing transformation into MIL‐140A, which is another Zr‐MOF that shows good catalytic activity toward PET degradation under similar reaction conditions. These results illustrate the diversity of applications for Zr‐MOFs and establish MOFs as a new class of polymer degradation catalysts with the potential to address long‐standing challenges associated with plastic waste.

     
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  7. Abstract

    Polyethylene terephthalate (PET) is utilized as one of the most popular consumer plastics worldwide, but difficulties associated with recycling PET have generated a severe environmental crisis with most PET ending its lifecycle in landfills. We report that zirconium‐based metal–organic framework (Zr‐MOF) UiO‐66 deconstructs waste PET into the building blocks terephthalic acid (TA) and mono‐methyl terephthalate (MMT) within 24 hours at 260 °C (total yield of 98 % under 1 atm H2and 81 % under 1 atm Ar). Extensive structural characterization studies reveal that during the degradation process, UiO‐66 undergoes an intriguing transformation into MIL‐140A, which is another Zr‐MOF that shows good catalytic activity toward PET degradation under similar reaction conditions. These results illustrate the diversity of applications for Zr‐MOFs and establish MOFs as a new class of polymer degradation catalysts with the potential to address long‐standing challenges associated with plastic waste.

     
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  8. Abstract

    Wearable personal protective equipment that is decorated with photoactive self‐cleaning materials capable of actively neutralizing biological pathogens is in high demand. Here, we developed a series of solution‐processable, crystalline porous materials capable of addressing this challenge. Textiles coated with these materials exhibit a broad range of functionalities, including spontaneous reactive oxygen species (ROS) generation upon absorption of daylight, and long‐term ROS storage in dark conditions. The ROS generation and storage abilities of these materials can be further improved through chemical engineering of the precursors without altering the three‐dimensional assembled superstructures. In comparison with traditional TiO2or C3N4self‐cleaning materials, the fluorinated molecular coating material HOF‐101‐F shows a 10‐ to 60‐fold enhancement of ROS generation and 10‐ to 20‐fold greater ROS storage ability. Our results pave the way for further developing self‐cleaning textile coatings for the rapid deactivation of highly infectious pathogenic bacteria under both daylight and light‐free conditions.

     
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