Synthesis and Temperature-Induced Morphological Control in a Hybrid Porous Iron-Phosphonate Nanomaterial and Its Excellent Catalytic Activity in the Synthesis of Benzimidazoles

A new organicinorganic hybrid porous ironphosphonate material, HPFP-1, has been synthesized under hydrothermal conditions by using hexamethylenediamine-N,N,N',N'-tetrakis-(methylphosphonic acid) (HDTMP) as the organophosphorus precursor. The morphology of this material was found to be different at three different temperatures. The material that was synthesized at 453 K showed a flake-like particle morphology and the material was highly crystalline. Whereas, the materials that were synthesized at 443 K and 423 K were semi-crystalline and showed rod-like- and spherical morphological features, respectively. SEM and TEM were employed to understand this change in particle morphology depending on the reaction temperature. Powder XRD analysis suggested the formation of a new tetragonal phase in HPFP-1 (a=11.313, c=15.825 angstrom; V=2025.659 angstrom 3). N2-sorption analysis suggested the existence of supermicropores and interparticle mesopores in these materials. Elemental- and thermal analyses, as well as FTIR spectroscopy, were employed to verify the composition and framework bonding of the material. The HPFP-1 material showed excellent catalytic activity for the synthesis of benzimidazole derivatives under mild liquid-phase reaction conditions.