Green Synthesis of Zeolitic Imidazolate Frameworks: A Review of Their Characterization and Industrial and Medical Applications

Abstract

Metal organic frameworks (MOF) are a class of hybrid networks of supramolecular solid materials comprising a large number of inorganic and organic linkers, all bound to metal ions in a well-organized fashion. Zeolitic imidazolate frameworks (ZIFs) are a sub-group of MOFs with imidazole as an organic linker to metals; it is rich in carbon, nitrogen, and transition metals. ZIFs combine the classical zeolite characteristics of thermal and chemical stability with pore-size tunability and the rich topological diversity of MOFs. Due to the energy crisis and the existence of organic solvents that lead to environmental hazards, considerable research efforts have been devoted to devising clean and sustainable synthesis routes for ZIFs to reduce the environmental impact of their preparation. Green chemistry is the key to sustainable development, as it will lead to new solutions to existing problems. Moreover, it will present opportunities for new processes and products and, at its heart, is scientific and technological innovation. The green chemistry approach seeks to redesign the materials that make up the basis of our society and our economy, including the materials that generate, store, and transport our energy, in ways that are benign for humans and the environment and that possess intrinsic sustainability. This study covers the principles of green chemistry as used in designing strategies for synthesizing greener, less toxic ZIFs the consume less energy to produce. First, the necessity of green methods in today’s society, their replacement of the usual non-green methods and their benefits are discussed; then, various methods for the green synthesis of ZIF compounds, such as hydrothermally, ionothermally, and by the electrospray technique, are considered. These methods use the least harmful and toxic substances, especially concerning organic solvents, and are also more economical. When a compound is synthesized by a green method, a question arises as to whether these compounds can replace the same compounds as synthesized by non-green methods. For example, is the thermal stability of these compounds (which is one of the most important features of ZIFs) preserved? Therefore, after studying the methods of identifying these compounds, in the last part, there is an in-depth discussion on the various applications of these green-synthesized compounds.

Acoustomicrofluidic Defect Engineering and Ligand Exchange in ZIF‐8 Metal–Organic Frameworks

“…Given the well known structure of pristine ZIF-8, that is, C 8 H 10 N 4 Zn, where each Zn atom is coordinated with 2 mIm linkers, complete framework decomposition is expected to lead to the formation of ZnO. Therefore, TGA curves of as-prepared samples were normalized so that end weights (i.e., the weight percentage of ZnO) are equal to 100 wt%; the stoichiometric weight prior to the start of decomposition, that is, at 400 °C, is thus ≈280% (experimentally, a weight of 285% for ZIF-8, similar to that here, is common [43][44][45] ). In particular, it can be seen that this weight diminishes with increasing acoustic exposure duration over 1, 3, and 12 h, decreasing from 280% to 279% after 1 and 3 h, respectively, and subsequently to 270% after 12 h of SRBW exposure.…”

Historical and contemporary perspectives on metal–organic frameworks for gas sensing applications: a review

“…45 ZIFs have been synthesized either through solvent techniques ( i.e. , solvothermal, 45,46 hydrothermal, 47,48 microwave-assisted, 49,50 and sol–gel synthesis 51,52 ), solvent-free techniques ( i.e. , mechanochemical 53,54 and accelerate aging 55 ), all while using less-toxic solvent derivatives ( i.e.…”

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

“…Afterward, different small-scale batch syntheses were described including room temperature or hydrothermal approaches and those using supercritical carbon dioxide (scCO 2 ), ionic liquids, microwave irradiation, electric current, ultrasounds, and deprotonating agents or surfactants (Figure ). , Larger-scale batch syntheses have been implemented by BASF for their commercially available ZIF-8 (Basolite Z1200) by electrochemical anodic dissolution and by Li et al as a CO 2 -aided approach . The increased space-time yield (STY) and improved mixing efficiency, homogeneity, and quality control of the final product can be provided by continuous approaches, such as microreactors and spray drying. , For instance, microreactors can be used for continuous flow synthesis of ZIF-8 with STY reaching 210,000 kg m –3 d –1 but with a low production rate (Table S1).…”