Life Cycle Assessment on Different Synthetic Routes of ZIF-8 Nanomaterials

Abstract

In the last twenty years, research activity around the environmental applications of metal–organic frameworks has bloomed due to their CO2 capture ability, tunable properties, porosity, and well-defined crystalline structure. Thus, hundreds of MOFs have been developed. However, the impact of their production on the environment has not been investigated as thoroughly as their potential applications. In this work, the environmental performance of various synthetic routes of MOF nanoparticles, in particular ZIF-8, is assessed through a life cycle assessment. For this purpose, five representative synthesis routes were considered, and synthesis data were obtained based on available literature. The synthesis included different solvents (de-ionized water, methanol, dimethylformamide) as well as different synthetic steps (i.e., hours of drying, stirring, precursor). The findings revealed that the main environmental weak points identified during production were: (a) the use of dimethylformamide (DMF) and methanol (MeOH) as substances impacting environmental sustainability, which accounted for more than 85% of the overall environmental impacts in those synthetic routes where they were utilized as solvents and as cleaning agents at the same time; (b) the electricity consumption, especially due to the Greek energy mix which is fossil-fuel dependent, and accounted for up to 13% of the overall environmental impacts in some synthetic routes. Nonetheless, for the optimization of the impacts provided by the energy use, suggestions are made based on the use of alternative, cleaner renewable energy sources, which (for the case of wind energy) will decrease the impacts by up to 2%.

A facile route for the recovery of the ligand of zeolitic imidazolate framework ZIF-94/SIM-1

“…3 In addition, the present study completes some of the recent attempts ( e.g. recycling solvents and reagents from the synthesis or spent mother liquors 12–17 in line with the high environmental impact of organic solvents in the MOF synthesis 18 ) to make the synthesis of MOFs more sustainable, none of them dealing with the dissolution of the MOF to purify and reuse its ligand. The reuse of this ligand from discarded ZIF-94/SIM-1 crystals would save an important part of the energy and resources needed to produce new ligand.…”

Research progress in metal–organic frameworks (MOFs) in CO2capture from post-combustion coal-fired flue gas: characteristics, preparation, modification and applications

“…They found that the solvents used in the cleaning and purification steps of MOF synthesis had an equal or greater impact on the environmental index, which should avoid the use or perform the reutilization of the solvent. Ntouros et al 130 adopted the LCA to investigate and evaluate the five synthetic routes for the production of ZIF-8 and found that deionized water as a solvent was more environmentally friendly than DMF and methanol. Hughes et al 131 investigated “basic” (no bed cooling during adsorption) and “modified” (bed cooling during adsorption) temperature swing adsorption (TSA) processes using dmpn-Mg 2 (dobpdc), respectively, and compared their process economics to the most advanced MEA capture systems.…”

Sustainable Production of Layered Bismuth Oxyhalides for Photocatalytic H2 Production

“…82−85 Ntouros et al explored five synthetic routes toward ZIF-8 nanomaterials. 82 They showed that the use of methanol as a solvent accounts for 35% of the mean environmental impact, while this metric increases to 58% using DMF as a solvent. The use of deionized water as a solvent resulted in only 2% of the mean environmental impact, showing the negative impact of nonaqueous solvents.…”

“…We can look to the literature for LCA analyses of synthetic methods of other materials. − Ntouros et al explored five synthetic routes toward ZIF-8 nanomaterials . They showed that the use of methanol as a solvent accounts for 35% of the mean environmental impact, while this metric increases to 58% using DMF as a solvent.…”