Hierarchically porous amino-functionalized nanoMOF network anchored phosphomolybdic acid for oxidative desulfurization and shaping application

Abstract

The applications of hierarchically porous metal–organic frameworks (HP-MOFs) against traditional microporous counterparts for oxidative desulfurization (ODS) have triggered wide research interests due to their highly exposed accessible active sites and fast mass transfer of substrate molecules, particularly for the large-sized refractory sulfur compounds. Herein, a series of hierarchically porous amino-functionalized Zr-MOFs (HP-UiO-66-NH2-X) network with controllable mesopore sizes (3.5–9.2 nm) were firstly prepared through a template-free method, which were further utilized as anchoring support to bind the active phosphomolybdic acid (PMA) via the strong host–guest interaction to catalyze the ODS reaction. Benefitting from the hierarchically porous structure, accessible active sites and the strong host–guest interaction, the resultant PMA/HP-UiO-66-NH2-X exhibited excellent ODS performance, of which, the PMA/HP-UiO-66-NH2-9 with an appropriate mesopore size (4.0 nm) showed the highest catalytic activity, achieving a 99.9% removal of dibenzothiophene (DBT) within 60 min at 50 °C, far exceeding the microporous sample and PMA/HP-UiO-66. Furthermore, the scavenger experiments confirmed that •OH radical was the main reactive species and the density functional theory (DFT) calculations revealed that electron transfer (from amino group to PMA) made PMA react more easily with oxidant, thereby generating more •OH radical to promote the ODS reaction. Finally, from the industrial point of view, the powdered MOF nanoparticles (NPs) were in situ grown on the carboxymethyl cellulose (CMC) substrates and shaped into monolithic MOF-based catalysts, which still exhibited satisfying ODS performance in the case of model real fuel with good reusability, indicating its potential industrial application prospect.