Infinite-layer transition metal oxides with two-dimensional oxygen coordination exhibit intriguing electronic and magnetic properties due to strong in-plane orbital hybridization. The synthesis of this distinctive structure has primarily relied on kinetically controlled reduction of oxygen-rich phases featuring three-dimensional polyhedral oxygen coordination. Here, using in situ atomic-resolution electron microscopy, we scrutinize the intricate atomic-scale mechanisms of oxygen conduction leading to the transformation of SrFeO_2.5 to infinite-layer SrFeO₂. The oxygen release is highly anisotropic and governed by the lattice reorientation aligning the fast diffusion channels towards the outlet, which is facilitated by cooperative yet shuffle displacements of iron and oxygen ions. Accompanied with the oxygen release, the three-dimensional to two-dimensional reconfiguration of oxygen is facilitated by the lattice flexibility of FeO_x polyhedral layers, adopting multiple discrete transient states following the sequence determined by the least energy-costing pathways. Similar transformation mechanism may operate in cuprate and nickelate superconductors, which are isostructural with SrFeO₂.

具有二维氧配位的无限层过渡金属氧化物由于强的面内轨道杂化而表现出有趣的电子和磁性。这种独特结构的合成主要依赖于具有三维多面体氧配位的富氧相的动力学控制还原。在这里，我们使用原位原子分辨率电子显微镜，仔细研究了氧传导导致 SrFeO _2.5转变为无限层 SrFeO ₂的复杂原子尺度机制。氧的释放是高度各向异性的，并由晶格重新取向控制，将快速扩散通道对准出口，这是通过铁离子和氧离子的协同但洗牌位移来促进的。伴随着氧的释放，FeO _x多面体层的晶格灵活性促进了氧的三维到二维的重构，按照由最少能量消耗路径确定的顺序采用多个离散瞬态状态。类似的转变机制可以在与SrFeO ₂具有同构结构的铜酸盐和镍酸盐超导体中运行。