An N,N'-diethylformamide solvent-induced conversion cascade within a metal-organic framework single crystal

Area of Science:

• Materials Science
• Chemistry
• Crystallography

Background:

• Metal-organic frameworks (MOFs) are crystalline porous materials with diverse applications.
• Two-dimensional (2D) MOFs can be precursors for more complex three-dimensional (3D) structures.
• Understanding MOF transformations is key to designing advanced functional materials.

Purpose of the Study:

• To investigate the structural transformation of a 2D MOF upon immersion in a solution of trans-1,2-bis(4-pyridyl)ethylene (BPEE).
• To explore the cascade conversion of the resulting 3D MOF in N,N'-diethylformamide (DEF).
• To elucidate the dynamic structural interconversion pathways of MOFs.

Main Methods:

• Single-crystal X-ray diffraction was used to determine the structures of the MOFs.
• Crystals of the initial 2D MOF [Cd3(BTB)2(DEF)4]·2(DEF)0.5 (1) were immersed in BPEE solution to form 3D MOF [Cd3(BTB)2(BPEE)(H2O)2]·(BPEE)·xSol (2).
• MOF 2 crystals were subsequently immersed in DEF to induce cascade conversion into MOFs 3a and 4, and eventually back to MOF 1.

Main Results:

• The 2D MOF (1) transformed into an interpenetrated 3D MOF (2) upon exposure to BPEE.
• MOF 2 underwent a time-dependent cascade conversion in DEF, forming intermediate phases (3a, 4).
• The MOF system demonstrated reversibility, returning to the initial 2D MOF (1) after prolonged immersion in DEF.

Conclusions:

• The study demonstrates the dynamic structural interconversion capabilities of MOFs.
• The observed cascade conversion highlights the potential for designing responsive and switchable MOF materials.
• This work provides insights into the mechanisms governing MOF structural transformations and recyclability.