Although two-dimensional (2D) atomic layers, such as transition-metal chalcogenides, have been widely synthesized using techniques such as exfoliation^1,2,3 and vapour-phase growth^4,5, it is still challenging to obtain phase-controlled 2D structures^6,7,8. Here we demonstrate an effective synthesis strategy via the progressive transformation of non-van der Waals (non-vdW) solids to 2D vdW transition-metal chalcogenide layers with identified 2H (trigonal prismatic)/1T (octahedral) phases. The transformation, achieved by exposing non-vdW solids to chalcogen vapours, can be controlled using the enthalpies and vapour pressures of the reaction products. Heteroatom-substituted (such as yttrium and phosphorus) transition-metal chalcogenides can also be synthesized in this way, thus enabling a generic synthesis approach to engineering phase-selected 2D transition-metal chalcogenide structures with good stability at high temperatures (up to 1,373 kelvin) and achieving high-throughput production of monolayers. We anticipate that these 2D transition-metal chalcogenides will have broad applications for electronics, catalysis and energy storage.

尽管二维 (2D) 原子层，如过渡金属硫属化物，已使用剥离^1,2,3和气相生长^4,5等技术广泛合成，但获得相控二维仍然具有挑战性结构^6,7,8. 在这里，我们展示了一种有效的合成策略，即通过将非范德华（非 vdW）固体逐步转变为具有确定的 2H（三角棱柱）/1T（八面体）相的 2D vdW 过渡金属硫属化物层。通过将非 vdW 固体暴露于硫属元素蒸气而实现的转变可以使用反应产物的焓和蒸气压来控制。杂原子取代（如钇和磷）的过渡金属硫属化物也可以通过这种方式合成，因此可以采用通用合成方法来设计具有良好高温稳定性（高达 1,373 开尔文）的相选择二维过渡金属硫属化物结构) 并实现单层的高通量生产。