Starting from 7c as the monomer, its dimer (8c), trimer (9c), and pentamer (10c) were synthesized via Wittig reactions. In these reactions, the formyl and phosphonium groups react selectively, since the chloromethyl and dimethylacetal groups were inert under the reaction conditions. The macrocyclization was performed with 10d, which was derived from 10c and bears formyl and phosphonium groups to yield 11 in 67% The thus obtained Möbius belt 1 was characterized using high-resolution mass spectrometry (HRMS) and NMR spectroscopy. The high-resolution mass spectrum showed an isotope pattern with its highest peak at 3944.9449, which is in good agreement with the simulated pattern and mass number (m/z = 3944.9423) expected for C280H260O20 (for details, see Fig. in SI). The DFT-optimized structure of 1 shows C2-symmetry with a long (38 Å) and a short (30 Å) axis (Fig. ). The broadened signals in the 1 H NMR spectrum observed at 25 °C converged at 140 °C to eight assignable singlet signals (Fig. ). These results indicate that the twist moiety of the Möbius belt moves quickly around the belt at high temperature. As shown in Fig. , the molecular motion was simulated using density functional tight binding with molecular dynamics (DFTB-MD) calculation (for details, see the materials and method in SI). The photophysical properties of Möbius CNB 1 were also investigated. As shown in Fig. , absorption maxima at 389 and 409 nm as well as a small absorption peak at 477 nm were observed, and greenish-blue fluorescence with maxima at 480, 513, and 551 nm were observed upon excitation at 380 nm. Based on the fluorescence quantum yield (10%) and half-life (14.1 ns), the radiative and nonradiative decay rate constants (kr and knr) were estimated to be 7.1 × 10 6 s -1 and 6.4 × 10 7 s -1 , respectively. Time-dependent density functional theory (TD-DFT) calculations of 1 suggested that unlike in the D3h-symmetric (6,6)CNB, the S0→S1 transition (assignable to the small band at 477 nm) is symmetry-allowed (f = 0.6239), which reflects the lowered symmetry caused by the Möbius topology (see Fig. ). The topological chirality of 1 was also examined experimentally. Chiral separation of 1 was successfully achieved using chiral HPLC, and the circular dichroism (CD) spectrum of each fraction was collected (Fig. and Fig. ,6 in SI). Based on the CD spectra simulated using TD-DFT calculations (for details, see Fig. in SI), the first and second fractions were tentatively assigned to M-and P-chirality, respectively. In conclusion, we have successfully synthesized a Möbius carbon nanobelt (MCNB), i.e., a topological molecular nanocarbon with a twist on armchair carbon nanobelts (CNBs). The strategy of using a variant of the previously used CNB precursor, cyclo(dibromoparaphenylene-Z-ethenylene), with an odd number of units led to the discovery of a rational synthetic route to such MCNBs. DFT calculations of the intrinsic strain energies suggested that the synthesis of MCNBs with large sizes would be most promising, and therefore, (25,25)MCNB was selected as the target.