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We report the fabrication of three‑dimensional, interconnected networks of ultrathin carbon nanotubes (CNTs) embedded within the ~5 Å pores of zeolite ZSM‑5 crystals using a controlled chemical vapour deposition (CVD) process. Confinement within these sub‑nanometre channels yields CNTs with strongly one‑dimensional electronic characteristics, including pronounced van Hove singularities in the density of states. By introducing boron dopants during growth, we strategically tune the Fermi level toward a van Hove singularity, as supported by ab initio electronic‑structure calculations. This electronic tuning, combined with the intrinsic 3D connectivity of the CNT–zeolite framework, enables a dimensional crossover from 1D electronic states to a phase‑coherent, bulk superconducting state.

To establish the presence of superconductivity, we employ five complementary experimental probes—electrical resistivity, ac susceptibility, dc magnetization, specific heat, and point‑contact spectroscopy. All measurements consistently indicate a superconducting transition at ambient pressure with a critical temperature Tc in the range of 220–250 K. Simultaneous resistivity and ac‑susceptibility measurements reveal a three‑order‑of‑magnitude drop in resistance accompanied by the onset of a robust Meissner effect with nearly perfect diamagnetic screening. Point‑contact spectroscopy further uncovers a multigap superconducting state, with a dominant gap of approximately 30 meV, in reasonable agreement with expectations from Bardeen–Cooper–Schrieffer (BCS) theory. The differential conductance spectra exhibit clear particle–hole symmetry and evolve smoothly between the tunnelling and Andreev reflection regimes as the contact transparency is varied—behaviour uniquely characteristic of superconducting quasiparticles. Specific‑heat measurements show a distinct anomaly at the transition, reminiscent of signatures observed in high‑Tc cuprate superconductors.

Finally, we find that the application of very modest external pressure further enhances the superconducting transition temperature, pushing Tc above ambient temperature and suggesting that the system remains far from its optimal tuning point. These results collectively point to a new pathway for achieving high‑temperature superconductivity in engineered low‑dimensional carbon‑based materials.