Metal-organic frameworks and metal-organic framework-derived materials for denitrogenation of liquid fuel via adsorption and catalysis

The elimination of contaminants such as nitrogen-containing compounds (NCCs) from fuels is crucial because these impurities can cause several problems, including inactivating catalysts during fuel processing and decreasing fuel stability. The shortcomings of conventional hydrotreating procedures for NCC removal require new and advanced materials and methods. Adsorptive denitrogenation (ADN) and oxidative denitrogenation (ODN) are the two promising alternatives in terms of moderate operating conditions and the efficiency of creating clean fuels. In this review, the development of both the ADN and ODN processes are summarized in the view of the preparation methods and performances of the developed materials (particularly metal-organic frameworks (MOFs) and MOF-derived materials) and mechanisms (both adsorption and oxidation) in the removal of NCCs from fuels. The adsorption of NCCs over the MOFs could be interpreted via several mechanisms such as van der Waals force, 7C-7C interaction, H-bonding, and acid-base interaction. In addition, the oxidation of NCCs can be mainly attributed to the nucleophilic attack of an active oxygen species (which is produced by the interaction of the oxidant and the active site of a catalyst) onto the N of the NCCs. This review will encourage the scientific community to understand the importance and current state of the ADN/ODN processes, particularly by utilizing MOF/MOF-derived materials, and the strategies for developing more cost-effective and energy-efficient approaches for the denitrogenation of fuels.