Anisotropic thermal expansion of a 3D metal–organic framework with hydrophilic and hydrophobic pores

• Thermally induced structural change of a 3D MOF with a lattice fence topology was investigated.
• The structural change was analyzed by synchrotron X-ray diffraction patterns.
• Temperature change induces anisotropic thermal expansion/contraction of the MOF.
• Silica inclusion anisotropically changes the thermal responsiveness of the MOF.

A 3D flexible metal–organic framework (MOF) with 1D hydrophilic and hydrophobic pores shows anisotropic thermal expansion with relatively large thermal expansion coefficient (αa=−21×10−6 K−1 and αc=79×10−6 K−1) between 133 K and 383 K. Temperature change gives deformation of both pores, which expand in diameter and elongate in length on cooling and vice versa. The thermally induced structural change should be derived from a unique framework topology like “lattice fence”. Silica accommodation changes not only the nature of the MOF but also thermal responsiveness of the MOF. Since the hydrophobic pores in the material are selectively blocked by the silica, the MOF with the silica is considered as a hydrophilic microporous material. Furthermore, inclusion of silica resulted in a drastic pore contraction in diameter and anisotropically changed the thermal responsiveness of the MOF.

A 3D metal–organic framework with hydrophilic and hydrophobic pores shows anisotropic thermal expansion behavior. The influence of silica filler in the hydrophobic pore was investigated.Figure optionsDownload as PowerPoint slide