BN-MoS 2) 1D van der Waals heterostructure with a diameter of only 5 nm, which may be the smallest metal-insulator-semiconductor device proven to date. [6] In addition, all of these prior works demonstrated the potential of 1D materials as high-current density conductors. [7] First-principles calculations expose that ultra-long ballistic phonon transmissions are generated by highly focused longitudinal phonons that propagate along one dimension, [8] and thermal conductivity may diverge under 1D limit conditions. [9] Therefore, synthesizing and studying 1D materials are conducive to our understanding of their unique thermal, optical, and electrical properties, thus further promoting various applications of such materials. At present, the growth of 1D van der Waals materials is mainly conducted by chemical vapor deposition (CVD) with the help of CNTs or BNNTs. CVD is an effective strategy for synthesizing layered materials with excellent electro-optical properties. However, large temperature differences (>10 °C) cause growth kinetics to deviate from equilibrium, and the synthesized layered materials usually have a lot of defects and grain boundaries. [10] According to the classical band theory, a large number of defects in a crystal will generate deep levels or trap states inevitably, which usually limits the carrier mobility. [11] Simultaneously, the halogen element is usually not a stable reactant for the CVD method, which also makes it unsuitable for the growth of binary van der Waals materials containing halogen atoms. Therefore, there are still many challenges for synthesizing high-quality and large-size single-crystal van der Waals materials in this method, especially for those containing halogen elements. [10,12] Alternatively, van der Waals materials with large crystal size and high crystal quality can be obtained by mechanical exfoliation, but it is difficult to get them controlled in one dimension. Therefore, for the growth of large-scale 1D van der Waals materials, a new and efficient synthesis method is urgently needed. Here, we propose a new method that combines organic liquid phase synthesis and post-annealing. With the singlechain structure of CdBr 2 •4H 2 O, we successfully synthesized the high-quality and large-sized CdBr 2 van der Waals micro/nanobelts. Compared with CVD, this synthetic method reported in this article has shown two obvious advantages in growing highquality, large-size 1D van der Waals materials. First, according to the crystal growth thermodynamics and defect formation mechanism, [13] there is almost no temperature difference (<0.1 °C) between the crystal and solution. Liquid phase synthesis can Recently, 1D van der Waals materials with appealing optoelectronic properties different from 2D layered materials have attracted widespread attention. However, the existing methods are incapable of growing the high-quality and large-size 1D van der Waals materials to a certain extent. Here, a new method of organic liquid phase synthesis followed by annealing is proposed, which overcomes th...