Single‐crystal‐to‐single‐crystal (SCSC) transformations have received considerable interest in crystal engineering, owing to providing a key platform for creating new materials. However, because of the limited tolerance of chemical bonds against the lattice strains, it is challenging to maintain the crystallinity when the structure changes dramatically. Here, a peculiar SCSC transformation from organic crystals to inorganic crystals, simultaneously achieving a drastic change in structure, connectivity, and dimension, is reported. As a demonstration, after reacting with liquid gallium, zeolitic imidazolate framework‐8 (ZIF‐8) can easily transform to 2D hydroxide single crystals. Interestingly, long‐range ordered metallic atoms of hydroxide inherited from the ordered atomic arrangement of ZIF‐8, but the connectivity is distinct. With good universality and extensibility, this transformation vastly expands the research scope of the SCSC transformations and provides a novel pathway for the synthesis of crystalline materials.

Interlayer coupling strength dichotomizes two-dimensional (2D) materials into layered and non-layered types. Traditionally, they can be regarded as atomic layers intrinsically linked via van der Waals (vdW) forces or covalent bonds, oriented orthogonally to their growth plane. In our work, we report an unprecedented material system that differentiates from layered and non-layered materials, termed quasi-layered domino-structured (QLDS) materials. Considering the skewed structure, the force orthogonal to the 2D QLDS-GaTe growth plane constitutes a synergistic blend of vdW forces and covalent bonds, with neither of them being perpendicular to the 2D growth plane. This feature endows remarkable anisotropy, second harmonic generation enhancement with a staggering susceptibility of 394.3 pm V−1, and outstanding hydrogen evolution reaction catalytic activity with an ultra-low overpotential of 41 mV at 10 mA cm−2 and a modest Tafel slope of 73 mV dec−1. These findings endow further applications arranged in nonlinear optics, sensors, and catalysis.