ZIF-8 modified by Pluronic P123 copolymer with enlarged pores and enhanced textural properties for CO2/CH4 and CO2/N2 separations

Biodiesel Production from Transesterification with Lipase from Pseudomonas cepacia Immobilized on Modified Structured Metal Organic Materials

This research presents the modification of MOF-199 and ZIF-8 using furfuryl alcohol (FA) as a carbon source to subsequently fix lipase from Pseudomonas cepacia and use these biocatalysts in the transesterification of African palm oil (APO). The need to overcome the disadvantages of free lipases in the biodiesel production process led to the use of metal organic framework (MOF)-type supports because they provide greater thermal stability and separation of the catalytic phase, thus improving the activity and efficiency in relation to the use of free lipase, disadvantages that could not be overcome with the use of other types of catalysts used in transesterification/esterification reactions for the production of biodiesel. The modification of MOFs ZIF-8 and MOF-199 with FA increases the pore volume which allows better immobilization of Pseudomonas cepacia lipase (PCL). The results show that these biocatalysts undergo transesterification with biodiesel yields above 90%. Additionally, studies were carried out on the effect of (1) enzyme loading, 2) enzyme immobilization time, (3) enzyme immobilization temperature, and (4) pH on the % immobilization of the enzyme and the specific activity. The results show that the highest immobilization efficiency for the FA@ZIF-8 support has a value of 91.2% when the load of this support was 3.5 mg/mg and has a specific activity of 142.5 U/g protein. The FA@MOF-199 support presented 80.3% enzyme immobilization and 125% U/g specific activity protein. We established that the specific activity increases in the period from 0.5 to 5.0 h for the systems under investigation. After this time, both the specific activity and the % efficiency of enzyme immobilization decrease. Therefore, 5.0 h (immobilization efficiency of 95 and 85% for FA@MOF-199, respectively) was chosen as the most appropriate time for PCL immobilization. Methods of adding methanol, with three and four steps, were tested, where biodiesel yields greater than 90% were obtained for the biocatalysts synthesized in this work (FA@ZIF-8-PCL and FA@MOF-199-PCL) and above 70% for free PCL, and the maximum yield was reached at a molar ratio between methanol and APO of 4:1 when using the one-step method under the same reaction conditions (as mentioned above). Only the results of FA@ZIF-8-PCL are presented here; however, it should be noted that the results for biocatalyst FA@MOF-199-PCL and lipase-free PCL presented the same behavior. The order of biocatalyst performance was FA@ZIF-8-PCL > FA@MOF-199-PCL > PCL-Free, which demonstrates that the use of FA as a modifier is a novel aspect in the conversion of palm oil into biodiesel components.

Different Agglomeration Processes Induced by the Varied Interaction of Fe-Fe Analogues with Differently Charged Surfactants

The catalytic activity of Prussian blue analogues (PBAs) is mainly tuned via the control of material sizes and morphologies. However, the shapes and sizes of many PBAs are difficult to control. In this work, a facile approach is demonstrated using differently charged surfactants to tune the catalytic activity of PBAs. Fe-Fe PBAs prepared with non-ionic P123, cationic cetyltrimethylammonium bromide, and anionic sodium dodecyl sulfate are chosen to study the effect of surfactant charges on the catalytic activity. The transesterification of propylene carbonate to dimethyl carbonate by methanol is selected as a model reaction. Owing to the different agglomeration processes of PB particles after modified with differently charged surfactants, significantly varied shapes and sizes were observed. Accordingly, the catalytic activity is greatly varied by adding surfactants. The different catalytic activities may arise from the different behaviors of agglomeration of PB particles after surfactant modification as well as the material size and shape changes. Besides, apparent activation energies for PBs adding different surfactants were derived. Finally, the agglomeration mechanism of PB particles in the presence of differently charged surfactants was proposed.

A simple and versatile synthesis strategy of hollow MOFs for CO2 separation and catalysis

A novel single-solvent-interfacial strategy is proposed to synthesize hollow MOFs, fabricated at the two-phase interface originated from the self-deliquescence of hydration water in the metallic precursors and the solvents with low water solubility. The as-fabricated HMOFs with hierarchically porous structures exhibit significant enhancement in CO₂ separation and catalysis.