A three-dimensional π-conjugated polyradicaloid molecular cage c -Ph14 , consisting of three Chichibabin's hydrocarbon motifs connected by two benzene-1,3,5-triyl bridgeheads, was synthesized. Compared with its linear model compound l -Ph4 , the prism-like c -Ph14 has a more rigid structure, which shows significant impact on the molecular dynamics, stability, and electronic properties. A higher rotation energy barrier for the quinoidal biphenyl units was determined in c -Ph14 (15.64 kcal/mol) than that of l -Ph4 (11.40 kcal/mol) according to variable-temperature NMR measurements, leading to improved stability, a smaller diradical character, and an increased singlet-triplet energy gap. The pressure-dependent Raman spectroscopic studies on the rigid cage c -Ph14 revealed a quinoidal-to-aromatic transformation along the biphenyl bridges. In addition, the ellipsoidal cavity in the cage allowed selective encapsulation of fullerene C 70 over C 60 , with an associate constant of about 1.43 × 10 4 M -1 . Moreover, c -Ph14 and l -Ph4 exhibited similar redox behavior and their cationic species ( c -Ph14 6+ and l -Ph4 2+ ) were obtained by chemical oxidation, and the structures were identified by X-ray crystallographic analysis. The biphenyl unit showed a twisted conformation in l -Ph4 2+ and remained coplanarity in c -Ph14 6+ . Notably, molecules of c -Ph14 6+ form a one-dimensional columnar structure via close π-π stacking between the bridgeheads.