Recent trends in the application of metal-organic frameworks (MOFs) for the removal of toxic dyes and their removal mechanism-a review

Nowadays, water pollution is considered as a global concern and is rapidly increasing due to industrialization and other human activities. Unused dyes discharged from different industries without proper treatments are the major sources of water pollution. Thus, the removal of these dyes from wastewater has highly attracted scientific community to solve such environmental problems. To date, various adsorbents were synthesized and analyzed for the removal of dyes. Among the adsorbents, metal-organic frameworks (MOFs) are very promising as they possess a very high surface area with internal porous structures and hence, the dye removal efficiency is very high. The main objective of the review is to present a complete survey on the recently synthesized MOFs and their hybrid systems for dye removal. The removal efficiency of dye has been discussed in light of the surface areas and surface charges of MOFs. As per the literature, surface properties of MOFs strongly depend on the synthetic routes, and the composites of MOFs show a fast and higher dye removal efficiency. In addition, the maximum adsorption capacities of bare and hybrid MOFs have been critically discussed. Also, the adsorption mechanism of both cationic and anionic dyes on MOFs have been elucidated. Further, the reusability of the composite MOFs have been identified and discussed. Additionally, the present and future perspectives of MOFs in dye removal have been presented. Overall, MOFs can act as a promising and potential adsorbent for rapid and efficient removal of various dyes from wastewater.