Ionic Liquid Templated Ordered Hexagonal Mesoporous Iron Phosphate Molecular Sieves: A Highly Effective Heterogeneous Catalysts with Remarkable Selectivity for Phenol Hydroxylation Reaction

A highly organized hexagonal mesoporous iron phosphate framework structure with the designation HMI‐41 was successfully synthesized for the first‐time in a reproducible way using imidazolium‐based ionic liquid as structure directing agent. The unique templating properties of ionic liquid generated a highly ordered well‐crystallized mesoporous matrix having high surface area (445 m2 g−1), thicker pore wall (2.1 nm) and narrow pore size distribution (3.1 nm). The presence of active sites within a tetrahedral framework structure made the novel HMI‐41 catalyst highly effective for phenol hydroxylation in an acidic medium with hydrogen peroxide as the oxidant. The catalyst exhibited outstanding performance, achieving an impressive 80% hydroquinone selectivity and 21% phenol conversion with a hydroquinone‐to‐catechol ratio of seven, which is the highest value ever reported. A novel and highly ordered hexagonal mesoporous iron phosphate, designated as HMI‐41, was synthesized using a long chain ionic liquid, HDmimCl, as structure‐directing agent. The presence of high crystallinity, large surface area, huge pore volume and thicker pore walls makes these materials an excellent catalyst for selective hydroxylation of phenol to hydroquinone with a quinone‐to‐catechol ratio as high as seven. The aromatic planar 2D‐head group of ionic liquid has a stronger tendency to form highly ordered micelles owing to their hydrogen bonding ability and polarizability, leading to a stable, well‐ordered mesostructured iron phosphate.