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

Abstract

We report the scale-up of a batch solid synthesis of zeolitic imidazolate framework-8 (ZIF-8) for reactive extrusion. The crystalline product forms in the extruder directly under the mixture of solid 2-methylimidazole and basic zinc carbonate in the presence of a catalytic amount of liquid. The process parameters such as temperature, liquid type, feeding rate, and linker excess were optimized using the setup specifically designed for in situ Raman spectroscopy. Highly crystalline ZIF-8 with a Brunauer–Emmett–Teller (BET) surface area of 1816 m2 g–1 was quantitatively prepared at mild temperature using a catalytic amount of ethanol and a small excess of the linker. Finally, we developed a simple and comprehensive approach to evaluating the environmental friendliness and scalability of metal–organic framework (MOF) syntheses in view of their large-scale production.

Emerging transmission electron microscopy solutions for electrocatalysts: from synthesis to deactivation

“…Understanding the growth mechanism of MOFs is hence interesting in the design of catalysts for various applications. A series of in situ studies such as in situ FTIR, 71,72 in situ NMR, 73,74 in situ Raman, 75 and in situ XRD 76,77 have provided useful knowledge on the nucleation of MOFs, while LC-TEM provides the most direct evidence. 78–82 Unlike the nucleation of metal nanoparticles, MOFs are formed by connecting metal ions with organic ligands.…”

Continuous Fluid Catalytic Reactor Constructed Based on In Situ Growth of MOF Immobilized Enzyme on Ordered Silk Fabric

“…Recently, metal–organic frameworks (MOFs) have been widely used as protective shells for enzymes. − Research has shown that MOF shells can enhance their biochemical properties such as thermal stability, reusability, organic solvent resistance, and the stability of encapsulated enzymes through structural constraints. , In addition, the strong interaction between metal ions and imidazole esters enables ZIF-8 to maintain structural integrity in common solvents, including water . Moreover, the synthetic conditions of MOF immobilized enzymes are “green”, without heating, pressure, or organic solvents, which has a positive impact on green chemistry. − However, MOFs are crystalline powders with practical limitations such as easy aggregation and recycling difficulties. In addition, they can only be used in stirred reactions and not in continuous fluid catalytic reactions, resulting in low reaction efficiencies. ,− Therefore, the application of enzyme immobilization in continuous microfluidic reactors has aroused great interest.…”

“…In addition, they can only be used in stirred reactions and not in continuous fluid catalytic reactions, resulting in low reaction efficiencies. ,− Therefore, the application of enzyme immobilization in continuous microfluidic reactors has aroused great interest. For example, wall-coated reactors and packed-bed reactors that can achieve continuous production and long-term reuse have been successfully developed, but they still have some limitations: low amount of fixed catalyst, high cost, cumbersome packaging operations, and low mass transfer efficiency. − Using monolithic materials may be a good choice.…”