Curvature-Enhanced and Chirality-Modulated Anomalous Thermal Transport in Pentagonal Covalent Organic Framework Nanotubes

Abstract The emergence of covalent organic framework (COF) nanotubes extends tubular materials from rigid atomic networks to flexible molecular frameworks, yet their thermal transport properties remain unexplored. Here, based on an experimentally synthesized two-dimensional pentagonal COF (penta-COF), we construct a series of one-dimensional nanotubes and systematically investigate their axial thermal conductivity (κaxial) across the curvature and chirality parameter spaces. Using molecular dynamics simulations powered by a fine-tuned universal machine-learning potential, we uncover an anomalous curvature-enhanced thermal transport (κaxial ∼ 1/R1.31), opposite to the curvature-suppressed behavior commonly observed in conventional atom-based nanotubes. Moreover, at nearly constant radius, κaxial exhibits a pronounced dependence on chirality. Structural and vibrational analyses reveal that curvature acts as a geometric confinement field that suppresses disordered vibrations of flexible organic linkers and enhances conformational ordering, thereby improving the transport efficiency of low-frequency phonons. Further symmetry-guided analysis shows that the chirality dependence originates from a competition between the chirality-induced axial-misalignment penalty associated with the intrinsic elastic anisotropy of the pentagonal parent lattice and the conformational-ordering enhancement induced by rolling-driven symmetry reduction and strain homogenization. These findings reveal an unconventional geometry-phonon coupling mechanism in penta-COF nanotubes, and establish curvature and chirality as effective design parameters for tuning thermal transport in molecule-based one-dimensional pentagonal materials.