Recent advances on application of Metal-Organic framework based catalysts in biodiesel production Process: A review of catalyst types and Activity, challenges and opportunities

Metal-organic frameworks (MOFs), as a class of crystalline porous coordinated materials, have become significant candidates in various applications through their outstanding characteristics such as high surface area, large pore size, tunable porosity, and high thermal stability. Therefore, MOFs are capable of being used as heterogeneous catalysts directly, or as carriers for homogenous catalysts to enhance their surface area, stability, and recovery. One of the fields of catalytic activities of MOFs is accelerating the rate of biodiesel production. Biodiesel is a clean and renewable fuel made by esterification of free fatty acids (FFAs) or transesterification of triglycerides. FFAs and triglycerides can be provided from different sources; edible oils, non-edible oils, algal lipids, etc. To carry out esterification/transesterification reactions, a decent catalyst with proper acidic or basic properties is required. The catalyst is mostly preferred to be heterogenous to overcome separation challenges. Here, a comprehensive review has been conducted on studies from 2014 onwards that focus on using different types of MOFs as heterogeneous catalysts or as supports for immobilizing other species such as heteropoly acids, ionic liquids, and enzymes for biodiesel production process. Most of the studies have exhibited satisfying results, with biodiesel yield exceeding 90%, and having excellent catalyst’s reusability with nearly the same functionality as the first cycle. Different methods of MOFs synthesis, their characterization by using different techniques and other applications of MOFs have been discussed as well. Consequently, a brief conclusion about the most favored MOFs in biodiesel production and their future perspective is presented.