Green synthesize of nano-MOF-ethylcellulose composite fibers for efficient adsorption of Congo red from water.

Two novel MOF- ethyl cellulose (EC)- based nanocomposites have been designed and synthesized in water by electrospinning and applied for adsorption of congo red (CR) in water. Nano- Zeolitic Imidazolate Framework-67 (ZIF-67), and Materials of Institute Lavoisier (MIL-88A) were synthesized in aqueous solutions by a green method. To enhance the dye adsorption capacity and stability of MOFs, they have been incorporated into EC nanofiber to prepare composite adsorbents. The performance of both composites in the absorption of CR, a common pollutant in some industrial wastewaters, has then been investigated. Various parameters including initial dye concentration, the dosage of the adsorbent, pH, temperature and contact time were optimized. The results indicated 99.8 and 90.9% adsorption of CR by EC/ZIF-67 and EC/MIL-88A, respectively at pH = 7 and temperature at 25 °C after 50 min. Furthermore, the synthesized composites were separated conveniently and successfully reused five times without significant loss of their adsorption activity. For both composites, the adsorption behavior can be explained by pseudo-second-order kinetics, Intraparticular diffiusion and Elovich models demonstrated that the experimental data well matched to the pseudo-second-order kinetics. Intraparticular diffiusion model showed that the adsorption of CR on EC/ZIF-67 and EC/MIL-88a took place in one and two steps, respectively. Freundlich isotherm models and thermodynamic analysis indicated exothermic and spontaneous adsorption.

Carbonic Anhydrase-Embedded ZIF-8 Electrospun PVA Fibers as an Excellent Biocatalyst Candidate.

There is a growing concern that the increasing concentration of CO2 in the atmosphere contributes to a potential negative impact on global climate change. To deal with this problem, developing a set of innovative, practical technologies is essential. In the present study, maximizing the CO2 utilization and precipitation as CaCO3 was evaluated. In this manner, bovine carbonic anhydrase (BCA) was embedded into the microporous zeolite imidazolate framework, ZIF-8, via physical absorption and encapsulation. Running as crystal seeds, these nanocomposites (enzyme-embedded MOFs) were in situ grown on the cross-linked electrospun polyvinyl alcohol (CPVA). The prepared composites displayed much higher stability against denaturants, high temperatures, and acidic media than free BCA, and BCA immobilized into or on ZIF-8. During 37 days of storage period study, BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA maintained more than 99 and 75% of their initial activity, respectively. The composition of BCA@ZIF-8 and BCA/ZIF-8 with CPVA improved stability for consecutive usage in recovery reactions, recycling easiness, and greater control over the catalytic process. The amounts of calcium carbonate obtained by one mg each of fresh BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA were 55.45 and 49.15 mg, respectively. The precipitated calcium carbonate by BCA@ZIF-8/CPVA reached 64.8% of the initial run, while this amount was 43.6% for BCA/ZIF-8/CPVA after eight cycles. These results indicated that the BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA fibers could be efficiently applied to CO2 sequestration.

Novel bovine carbonic anhydrase encapsulated in a metal-organic framework: a new platform for biomimetic sequestration of CO2.

In this work, maximizing the utilization of CO2 and its precipitation as CaCO3 by using immobilized bovine carbonic anhydrase (BCA) was evaluated. In this way, selection of suitable carriers which have a gas adsorption function would enhance the CO2 sequestration efficiency of the carbonic anhydrase (CA). So a metal-organic framework (MOF), an excellent material for gas adsorption and enzyme immobilization was used. In this manner, BCA was encapsulated into the microporous zeolite imidazolate framework, ZIF-8, for the first time, using a bottle-around-a-ship method. Systematic characterization including powder X-ray diffraction (PXRD), UV-vis, and Fourier transform infrared (FT-IR) spectroscopies, BET, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) confirmed that the entrapment of BCA molecules was successfully achieved during the crystal growth of ZIF-8 with an enzyme loading of ca. 100 ± 1.2 mg g-1 of BCA-ZIF-8. Optimization of the matrix for increasing the stability of the enzyme in an encapsulated form is the main aim of the present study. The de novo approach was proposed because this method provides better enzyme protection from degradation, minimizes enzyme leaching and enables multiple reuse. Then, the influence of different parameters, including pH, temperature, storage and reusability, was evaluated for enzyme@MOF composites versus free enzymes. The prepared biocatalyst exhibited outstanding activity in a wide pH and temperature range and demonstrates high storage stability up to 37 days. This efficient and simple association procedure seems well-adapted to produce an enzymatic bio-catalyst for biocatalytic hydration of CO2. The FT-IR analysis revealed that the structure of BCA was well maintained during the encapsulation process. The thermal stability and reusability of the BCA-ZIF-8 increased noticeably due to the structural rigidity and confinement of the ZIF-8 scaffolds. These two parameters are very important for practical applications.