Dual Chemical Scissors Strategy Enables 1D Antimony Selenates with Ultraviolet Nonlinear Optical Properties

The rational, function-driven design of advanced inorganic functional materials remains a significant challenge, primarily attributed to their inherently complex and highly connected 3D frameworks of most oxide-based systems. Herein, we report a "dual chemical scissors" strategy that synergistically combines the effects of fluoride ions and stereochemically active lone pairs to precisely modulate local coordination environments and enable controlled dimensional reduction. Using this approach, we successfully synthesized the first series of non-centrosymmetric 1D antimony selenates-RbSbF₂SeO₄ (I), Rb₂Sb₂F₆SeO₄ (II), and Rb₂Sb₃F₉SeO₄ (III). These compounds feature well-defined helical chain structures constructed from SbO_xF_y polyhedra and SeO₄ tetrahedra, resulting in pronounced optical anisotropy and robust nonlinear optical (NLO) properties. Among the series, RbSbF₂SeO₄ (I) stands out with an exceptional combination of a broad optical transparency window (0.26-10 µm), a strong second-harmonic generation response (5.4 × KDP), and moderate birefringence (0.12 at 546 nm), positioning it as a highly promising candidate for ultraviolet NLO applications. This work establishes a powerful and generalizable structural design paradigm for constructing polar low-dimensional architectures and underscores the effectiveness of targeted coordination modulation in advancing high-performance optical materials.