Physics

Organic chemistry

Covalent bond

Crystallography

Crystal structure

Engineering

Catalysis

Chemistry

Condensation

Imine

Interlocking

Covalent organic framework

Square pyramidal molecular geometry

Mechanical engineering

Thermodynamics

Journal of the American Chemical Society

A new mode of mechanical entanglement in extended structures is described where 1D organic ribbons of corner-sharing squares are mutually interlocked to form 3D woven covalent organic framework-500, COF-500. Reaction of aldehyde-functionalized tetrahedral Cu(PDB)2PO2Ph2 complexes (PDB = 4,4'-(1,10-phenanthroline-2,9-diyl)dibenzaldehyde) with rectangular tetratopic ETTBA (4',4‴,4''''',4''''‴-(ethene-1,1,2,2-tetrayl)tetrakis([1,1'-biphenyl]-4-amine)) linkers through imine condensation, yielded a crystalline porous metalated COF, COF-500-Cu, with pts topology. Upon removal of the Cu(I) ions, the individual 1D square ribbons in the demetalated form (COF-500) are held together only by mechanical interlocking of rings, which allows their collective movement to produce a narrow-pore form, as evidenced by nitrogen adsorption and solid-state photoluminescence studies. When exposed to tetrahydrofuran vapor, the interlocking ribbons can dynamically move away from each other to reopen up the structure. The structural integrity of COF-500 is maintained during its dynamics because the constituent square ribbons cannot part company due to spatial confinement imparted by their interlocking nature.

3D Covalent Organic Frameworks of Interlocking 1D Square Ribbons