Two-dimensional (2D) materials with multiphase, multielement crystals such as transition metal chalcogenides (TMCs) (based on V, Cr, Mn, Fe, Cd, Pt and Pd) and transition metal phosphorous chalcogenides (TMPCs) offer a unique platform to explore novel physical phenomena. However, the synthesis of a single-phase/single-composition crystal of these 2D materials via chemical vapour deposition is still challenging. Here we unravel a competitive-chemical-reaction-based growth mechanism to manipulate the nucleation and growth rate. Based on the growth mechanism, 67 types of TMCs and TMPCs with a defined phase, controllable structure and tunable component can be realized. The ferromagnetism and superconductivity in FeX_y can be tuned by the y value, such as superconductivity observed in FeX and ferromagnetism in FeS₂ monolayers, demonstrating the high quality of as-grown 2D materials. This work paves the way for the multidisciplinary exploration of 2D TMPCs and TMCs with unique properties.

具有多相、多元素晶体的二维 (2D) 材料，例如过渡金属硫族化物 (TMC)（基于 V、Cr、Mn、Fe、Cd、Pt 和 Pd）和过渡金属磷硫族化物 (TMPC)，提供了一个独特的平台探索新颖的物理现象。然而，通过化学气相沉积合成这些二维材料的单相/单组分晶体仍然具有挑战性。在这里，我们揭示了一种基于竞争化学反应的生长机制来控制成核和生长速率。基于该生长机制，可实现67种相位确定、结构可控、组分可调的TMCs和TMPCs。_{FeX y}中的铁磁性和超导性可以通过y来调节值，例如在 FeX 中观察到的超导性和在 FeS ₂单层中观察到的铁磁性，证明了生长态二维材料的高质量。这项工作为具有独特属性的二维 TMPC 和 TMC 的多学科探索铺平了道路。