Comparison Between Conventional Solvothermal and Aqueous Solution-based Production of UiO-66-NH2: Life Cycle Assessment, Techno-economic Assessment, and Implications for CO2 Capture and Storage

Abstract

Metal-organic frameworks (MOFs) are a new class of materials that has shown great potential in catalysis, sensing, separations, and carbon capture and storage. Conventionally, MOFs are synthesized at lab-scale using organic solvent-based systems, leading to high environmental burdens and high operating costs, which ultimately hinders the large-scale production and application of MOFs. Aqueous synthesis of MOFs overcomes such difficulty by eliminating the organic solvent, which makes it an environmentalfriendlier and economically-favorable alternative to the current production method. However, further quantitative analysis is required to compare the environmental and economic performances of the two methods. Here, we used life cycle assessment (LCA) coupled with techno-economic analysis (TEA) to evaluate the environmental and economic performances of different UiO-66-NH2 production methods. When the solvothermal method was replaced by the aqueous solution-based method, the LCA and TEA results suggest the environmental burdens and cost of UiO-66-NH2 production were reduced by up to 91% and 84%, respectively. By using aqueous solution-based method, the cradle to gate carbon footprint and production cost of UiO-66-NH2 were estimated to be 43 kg CO2 eq/kg and $15.8/kg, respectively. We further applied our LCA results to reassess the role of UiO-66-NH2 in carbon capture and storage (CCS) and compare its environmental performance with current benchmark (amine-based solvent). Our results show that UiO-66-NH2 could potentially have better environmental performance than the amine-based solvent if the number of regeneration cycles is greater than 1513. This work is the first comprehensive LCA-TEA study that quantifies the substantial environmental and economic benefits of using the aqueous solution-based systems to produce UiO-66-NH2, and the analysis in this work is intended to be a starting point for further systematic studies on the full life-cycle impacts of MOFs.