Synthetic chemists have mastered the craft of interlocking discrete molecular entities into complex entangled architectures. Progress in synthetic interlocking organic molecules includes knots, catenanes, rotaxanes, interlocking cages, and most recently the synthesis of 1D linear or branched [n]polycatenane chains of limited length ([n] ~100). However, the analogous chemistry pertaining to infinite three-dimensional systems ([∞]catenane) remains undeveloped. We report a series of [∞]catenane covalent organic frameworks (termed catena-COFs). These were synthesized by linking 4,4'-(1,10-phenanthroline-2,9-diyl)dibenzaldehyde (PDB) to either of tris-(4-aminophenyl)-amine (TAPA), -methane (TAPM), or -methanol (TAPMol) through imine condensation (Figure 1a). These combinations give discrete adamantane-like polyhedra, catenated by virtue of the copper(I) ions templating a mutually embracing arrangement of PDBs (points-of-catenation) and ultimately resulting in infinite catena-COF-805, -806, and -807. The crystal structures of these COFs obtained from electron microscopy and x-ray diffraction were determined to be isoreticular and to adopt the bor-y structure type (Figure 1b, 1c). We wish to remark that if one considers the crystal size (~500 nm) and the observed size of the unit cell for catena-COF-805, the average crystal of this compound has ~5 million interlocking polyhedra. The previous record was held by an organic poly[n]catenane chain with n = 130, highlighting the prowess of reticular chemistry in the design and synthesis of extended organic catenanes.

Catenane covalent organic frameworks constructed from polyhedra

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