Self‐Assembled Hybrid Molybdenum Phosphonate Porous Nanomaterials and Their Catalytic Activity for the Synthesis of Benzimidazoles

Abstract

A new porous organic–inorganic hybrid molybdenum phosphonate nanomaterial (HMoP‐1) was synthesized through the reaction of benzene‐1,3,5‐triphosphonic acid and molybdenum(V) chloride under hydrothermal conditions in the absence of any structure‐directing agent. The morphology of the hybrid material was found to be different at different synthesis temperatures. The material synthesized at 423 K (HMoP‐1‐LT) has spherical particle morphology, and the material synthesized at 453 K (HMoP‐1‐HT) has self‐assembled flakelike morphology. Powder XRD, field‐emission SEM, high‐resolution TEM, N2 sorption, solid‐state 13C cross‐polarization magic‐angle spinning NMR and 31P magic‐angle spinning NMR analyses, X‐ray photoelectron spectroscopy, thermogravimetric differential thermal analysis, NH3 temperature‐programmed adsorption, and FTIR spectroscopic techniques were employed to characterize the samples and understand the morphological diversity. The orthorhombic crystal phase of the material was established through REFLEX and CELSIZ unit cell refinement programs. The calculated unit cell parameters of HMoP‐1‐HT are a=8.001(0.046) Å b=7.029 (0.039) Å, c=6.010 (0.036) Å; whereas HMoP‐1‐LT is amorphous in nature. HMoP‐1‐HT shows outstanding catalytic activity and high recycling efficiency for the green and efficient one‐pot condensation reaction for the synthesis of bioactive 2‐aryl benzimidazoles in excellent yields at room temperature.

Insights into mesoporous metal phosphonate hybrid materials for catalysis

“…109 The corresponding high yield was positively correlated with the surface area. As the surface area reduced, the mass transport through the porous channel was obviously impeded, which is reflected in the isolated yield of the product.…”

“…By contrast, iron phosphonates materials were catalytically active towards the synthesis of benzimidazole derivatives (Fig. 5), 110 but with a lower activity comparing with the molybdenum phosphonate counterparts 109 . This might be related to the moderate Lewis acidic strength of molybdenum due to the larger atomic radii than that of iron atoms.…”

“…It was speculated that the interaction between the catalyst and the carbonyl oxygen was strong enough to subsidize the effect of the substituents, while the amine groups of O-phenylenediamine were attached onto the carbonyl carbon. 109 The tertiary amine groups could help to eliminate the protons in the water-removal step, and this synergistic effect of the iron center and the tertiary amine groups catalyzed the synthesis of benzimidazole derivatives.…”

Recent Trends in the Synthesis of Benzimidazoles From o‐Phenylenediamine via Nanoparticles and Green Strategies Using Transition Metal Catalysts

“…The yield of the product was 40–95% by performing the reaction at room temperature in 30 min (Scheme , Table , entry 13). The catalyst was proved to have high surface area and uniform supermicropores and mesopores . Saikia et al .…”

Mesoporous Titania‐Iron(III) Oxide with Nanoscale Porosity and High Catalytic Activity for the Synthesis of β‐Amino Alcohols and Benzimidazole Derivatives

“…[ aldehydes [36] under oxidative conditions using various oxidizing agents and catalysts. Although the reaction can be promoted efficiently under these conditions, the catalysts employed are often homogeneous in nature, and some of these methods suffer from one or more disadvantages,s uch as the high cost of the catalysts, the use of hazardouso rganic solvents, prolonged reaction times, the occurrence of severals ide reactions, difficulty in the separation of the products from the reaction mixture, and the strongo xidizing nature of the reagents.…”