Sliding ferroelectricity is a recently observed polarity existing in two-dimensional materials. However, due to the weak polarization and poor electrical insulation in these materials, existing experimental evidences are indirect and mostly based on nanoscale transport properties or piezoresponse force microscopy. We report the direct observation of sliding ferroelectricity, using a high-quality amphidynamic single crystal (15-crown-5)Cd₃Cl₆, which possesses a large bandgap and so allows direct measurement of polarization–electric field hysteresis. This coordination polymer is a van der Waals material, which is composed of inorganic stators and organic rotators as determined by X-ray diffraction and NMR characterization. From density functional theory calculations, we find that after freezing the rotators, an electric dipole is generated in each layer driven by the geometric mechanism, while a comparable ferroelectric polarization originates from the interlayer sliding. The net polarization of these two components can be directly measured and manipulated. Our finding provides insight into low-dimensional ferroelectrics, especially control of the synchronous dynamics of rotating molecules and sliding layers in solids.

滑动铁电性是最近观察到的存在于二维材料中的极性。然而，由于这些材料的弱极化和电绝缘性差，现有的实验证据是间接的，主要基于纳米级传输特性或压电响应力显微镜。我们报告了使用高质量两性动力学单晶 (15-crown-5)Cd ₃ Cl _{6对滑动铁电的直接观察}，它具有较大的带隙，因此可以直接测量极化 - 电场滞后。这种配位聚合物是一种范德瓦尔斯材料，由 X 射线衍射和 NMR 表征确定的无机定子和有机旋转子组成。通过密度泛函理论计算，我们发现在冻结转子后，在几何机制的驱动下，在每一层中都会产生电偶极子，而类似的铁电极化则源于层间滑动。这两个组件的净极化可以直接测量和操作。我们的发现提供了对低维铁电体的深入了解，尤其是对固体中旋转分子和滑动层的同步动力学的控制。