Two ligand-functionalized Pb(II) metal-organic frameworks: structures and catalytic performances

Area of Science:

• Inorganic Chemistry
• Materials Science
• Crystallography

Background:

• Metal-organic frameworks (MOFs) are crystalline materials with tunable porous structures.
• Lead(II) based MOFs offer unique structural and chemical properties for various applications.
• Controlling framework dimensionality and pore size is crucial for selective guest interactions.

Purpose of the Study:

• To synthesize and characterize new microporous lead(II) metal-organic frameworks (MOFs).
• To investigate the structural differences and channel characteristics of the synthesized MOFs.
• To evaluate the adsorption properties and catalytic activity of the desolvated MOFs.

Main Methods:

• Solvothermal synthesis of lead(II) MOFs using a doubly functionalized ligand.
• Single-crystal X-ray diffraction for structural determination of the MOFs and guest exchange products.
• Gas adsorption/desorption isotherms and catalytic activity tests for Knoevenagel condensation.

Main Results:

• Two 3D lead(II) MOFs, [PbL(2)]·2DMF·6H(2)O (1) and [PbL(2)]·DMF·2H(2)O (2), were synthesized.
• Complex 1 features 1D rhombic channels (13 × 13 Å(2)), while complex 2 has smaller rectangular channels (13 × 8 Å(2)) due to structural reorganization.
• Single-crystal-to-single-crystal (SC-SC) guest exchange of DMF with benzene was observed in complex 2.
• Desolvated MOFs 1 and 2 showed preferential adsorption of water vapor over CO(2).
• Both MOFs demonstrated size-selective catalytic activity in the Knoevenagel condensation reaction.

Conclusions:

• The ligand and solvent choice significantly influence the resulting MOF structure and channel dimensions.
• The synthesized lead(II) MOFs exhibit potential for selective gas adsorption and heterogeneous catalysis.
• The observed SC-SC guest exchange highlights the dynamic nature and potential for modification of these MOF structures.