Hydrogen-Bond-Directed Modular Assembly of Polar Chains for Rational Construction of UV Nonlinear Optical Crystals

Non-centrosymmetric (NCS) materials underpin a host of emerging technologies-from high-power lasers to optical communications and sensors-yet their targeted design remains a formidable challenge. Herein, we introduce a "Hydrogen-Bond-Directed Modular Assembly" strategy for the rational construction of ultraviolet (UV) nonlinear optical (NLO) crystals. In this strategy, programmable hydrogen-bonding schemes serve as a predictive handle to propagate local asymmetry into a macroscopic polar network. Using an explicit modular design algorithm, we selected three building units-C₃H₃O₄ ^-, C₄H₅O₄ ^-, and C(NH₂)₃ ⁺-and assembled them into two one-dimensional polar chain modules, [C(NH₂)₃C₃H₃O₄]_∞ and [C(NH₂)₃C₄H₅O₄]_∞. These modules crystallize as two new UV NLO materials, C(NH₂)₃C₃H₃O₄ and C(NH₂)₃C₄H₅O₄, which exhibit excellent linear and nonlinear optical properties. By shifting the synthetic focus from serendipitous screening to hydrogen-bond-guided, module-level engineering, our strategy establishes a predictive framework for the a priori design of NCS structures with tailored properties.