MOFs in carbon capture-past, present and future

Abstract

• Microwave assisted solvo-thermal synthesis was found promising.· • Cu-BTC gave the highest CO 2 uptake was 9.59 mmol/g among various MOFs.· • Adsorption of CO 2 by MOFs mostly followed Pseudo second order kinetics along with Toth or modified Langmuir isotherm.· • Fixed and fluid bed type of contactors were the best suited for MOF based Carbon capture· • Photo-responsive MOFs have a great potential in future that could give a CO 2 uptake of 89 cc/g. Metal Organic Frame works (MOFs) are being widely used in carbon capture through adsorption and membrane techniques, which are yet to be commercialized. This is due to their high affinity towards acidic gases and exceptional characteristics such as crystallinity, structural stability, high surface area and flexible pore dimensions. In this review, wide range of topics viz., synthesis protocols, modifications employed to further improve their attributes, comprehensive comparison of different MOFs used in carbon capture, thermo-kinetics modelling studies, contactors and material screening. Every section has been discussed in detail in terms of developmental trends, future challenges and prospects besides summarizing in the form of comprehensive tables at a glance for the benefit of the readers. Solvo-thermal method was found to be the most effective synthesis method besides ultra-sonication and microwave assisted methods, which also gave very good crystalline structures. The copper ligand based unmodified Cu-BTC MOF gave the maximum CO 2 uptake value of 9.59 mmol/g at 273 K and 1 atm. Zn(Bmic)(AT) MOF was the only species to be tested at 353 K. Alternatively, a photo-responsive MOF, Mg-IRMOF-74-III functionalized with azopyridine gave a CO 2 uptake of 89 cc/g which is comparable to many of the conventional MOFs. Kinetics indicate MOF adsorption mostly follows pseudo second order reactions either along with Toth isotherms or modified Langmuir isotherms. Fixed and fluidized bed reactors perform the best in terms of carbon capture studies. Moisture affinity, active sites and crystallinity were found to be the best factors considered whilst screening of proper MOFs.