Three-fold interpenetrated Hofmann-type coordination polymers with high thermal stability

• Three Hofmann-type coordination polymers using the flexible N-donor ligand 1,4-bis((1H-imidazol-1-yl) methyl)benzene (bimb) were successfully synthesized and characterized. • The three compounds are isostructural and show 3D interpenetrated frameworks contributing to their notable thermal stability. • Compound {[Ni(bimb)₂][Pd(CN)₄]} is stable up to 300 °C, making it the most thermally robust imidazole-linked Hofmann-type structure to date. • This study advances Hofmann-type materials and highlights how deliberate ligand design can enhance performance. Three novel Hofmann-type coordination polymers, {[Cu(C₁₄H₁₄N₄)₂][Ni(CN)₄]}ₙ ( 1 ), {[Cu(C₁₄H₁₄N₄)₂][Pd(CN)₄]}ₙ ( 2 ), and {[Ni(C₁₄H₁₄N₄)₂][Pd(CN)₄]}ₙ ( 3 ), have been synthesized using the flexible N-donor ligand 1,4-bis((1H-imidazol-1-yl)methyl)benzene (bimb). Single-crystal X-ray diffraction confirms that all three compounds are isostructural, crystallizing in the triclinic P ‒1 space group and forming three-dimensional, threefold interpenetrated networks. The frameworks result from the coordination of Cu(II) or Ni(II) centers to [Ni(CN)₄]²⁻ or [Pd(CN)₄]²⁻ units, with structural integrity driven by the length and flexibility of the bimb linker. The Cu–N bimb and Cu–CN bond lengths are consistent with those observed in similar copper complexes, with slight variations attributable to the Jahn-Teller effect. The powder X-ray diffraction (PXRD) patterns confirm the crystalline nature and purity of the compounds. Variable-temperature powder X-ray diffraction (VT-PXRD) confirm the thermal robustness of 1 and 2 up to 200 °C and 250 °C, respectively. Thermogravimetric and calorimetric analyses reveal distinct decomposition behaviors, with no guest loss observed below 100 °C and reveal also their robust thermal stability. Hot-stage microscopy supports solid-state decomposition without melting for 1 and 3 . These results show that flexible imidazole ligands can be used to make interpenetrated Hofmann-type frameworks with potential for use in high-temperature applications such as gas separation and catalysis.