A remarkable adsorbent for denitrogenation of liquid fuel: Ethylenediaminetetraacetic acid-grafted metal–organic framework, MOF-808

Removal of nitrogen-containing compounds (NCCs) from the fuel is essential for clean energy. An efficient adsorbent with ample active sites was obtained via grafting ethylenediaminetetraacetic acid (EDTA) onto a metal–organic framework (MOF808). The obtained MOF808_EDTA was firstly applied in adsorptive removal of organics like NCCs from liquid; showed remarkable performances in NCCs removal. For example, MOF808_EDTA showed the maximum adsorption capacity (Q0) of 667 and 625 mg/g, respectively, in indole (IND) and quinoline (QUIN) removal from fuel. These Q0 values for QUIN and IND adsorption are the highest and third position, respectively, compared with reported results. Additionally, the Q0 values for IND and QUIN are > 10 times those of activated carbon. Importantly, the Q0 value, in volume/weight (0.57 cm3/g), is very close to the total pore volume (0.59 cm3/g) of MOF808_EDTA, suggesting very effective utilization of pores of the MOF in the adsorption. The adsorption of IND and QUIN over MOF808_EDTA could be interpreted with H-bonding and acid-base interactions, respectively, based on properties of adsorbates and functional groups on MOF808_EDTA and MOF808_EDTA-Na (where hydrogen in EDTA was replaced with Na). The new adsorbent MOF808_EDTA, which is highly reusable, is being suggested as a prominent adsorbent to remove NCCs, especially basic QUIN, from fuel. This work will pave the way to modify MOFs to introduce ample functional groups that will be effective in adsorption.