Synthesis, crystal structure, and catalytic performance of two 3-D supramolecular compounds: (C₇N₂H₇)₃(C₇N₂H₆) · PMo₁₂O₄₀· 2H₂O and (C₇N₂H₇)₃(C₇N₂H₆)₂· AsMo₁₂O₄₀· 3H₂O

Abstract

Two organic–inorganic compounds based on Keggin building blocks have been synthesized by hydrothermal methods, (C₇N₂H₇)₃(C₇N₂H₆) · PMo₁₂O₄₀· 2H₂O (1) and (C₇N₂H₇)₃(C₇N₂H₆)₂· AsMo₁₂O₄₀· 3H₂O (2) (C₇N₂H₆ = benzimidazole). Single-crystal X-ray analysis revealed that 1 crystallized in the triclinic system, P-1 space group with a = 9.8980(4) Å, b = 11.2893(4) Å, c = 25.8933(9) Å, α = 93.307(2)°, β = 90.630(2)°, γ = 108.330(2)°, V = 2740.68(18) ų, Z = 2, R ₁(F) = 0.0740, ωR ₂(F ²) = 0.1511, and S = 1.037; 2 crystallized in the triclinic system, P-1 space group with a = 12.3353(4) Å, b = 13.2649(4) Å, c = 20.2878(6) Å, α = 95.6630(10)°, β = 100.1720(10)°, γ = 99.3940(10)°, V = 3195.72(17) ų, Z = 2, R ₁(F) = 0.0329, ωR₂ (F ²) = 0.1236, and S = 1.088. The two compounds show a layer framework constructed from Keggin-polyoxoanion clusters and benzimidazole via hydrogen bonds and π–π stacking interactions, resulting in a 3-D supramolecular network. Both have high catalytic activity for oxidation of methanol. When the initial concentration of the methanol is 5.37 g m⁻³ in air and the flow velocity is 4.51 mL min⁻¹, methanol is completely eliminated at 150°C for 1 (160°C for 2).

Keywords:

• Keggin-polyoxoanion
• Hydrothermal technology
• Supramolecular compounds
• Methanol oxidation
• Catalytic elimination

Acknowledgments

This project was supported by the Hunan Provincial Science and Technology Plan Projects of China and Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, Hunan University of Science and Technology.