From helix to helical pores: solid-state crystalline conversions triggered by gas-solid reactions

Area of Science:

• Materials Science
• Inorganic Chemistry
• Crystallography

Background:

• 1D helical coordination polymers offer unique structural motifs.
• Metal-organic frameworks (MOFs) are versatile porous materials with diverse applications.
• Gas-solid reactions provide a pathway for solid-state transformations.

Purpose of the Study:

• To investigate the synthesis of novel 1D helical coordination polymers.
• To explore the solid-state crystalline conversion of these polymers into MOFs.
• To characterize the resulting MOF structure and formation mechanism.

Main Methods:

• Synthesis of CuBIm-Cl and CuBIm-Br coordination polymers using Cu2+ ions, halides, and 1,2-bis((5H-imidazol-4-yl)-methylene)hydrazine (BIm).
• Gas-solid reaction employing methylamine to induce crystalline conversion.
• Characterization of the starting materials and the final gyroidal MOF (STU-3) using techniques such as X-ray diffraction.

Main Results:

• Successfully synthesized two 1D helical coordination polymers: CuBIm-Cl and CuBIm-Br.
• Observed a solid-state crystalline conversion of CuBIm-Cl and CuBIm-Br to a gyroidal MOF, designated STU-3.
• STU-3 is composed of Cu ions and BIm ligands, showcasing a transformation from 1D chains to a 3D framework.

Conclusions:

• The study demonstrates a novel gas-solid reaction pathway for MOF synthesis.
• The observed transformation highlights the dynamic structural adaptability of coordination polymers.
• The formation of STU-3 provides a new gyroidal MOF with potential for various applications.