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—C 3 H 3 O 4 − , C 4 H 5 O 4 − , and C(NH 2 ) 3 + —and assembled them into two one‐dimensional polar chain modules, [C(NH 2 ) 3 C 3 H 3 O 4 ] ∞ and [C(NH 2 ) 3 C 4 H 5 O 4 ] ∞ . These modules crystallize as two new UV NLO materials, C(NH 2 ) 3 C 3 H 3 O 4 and C(NH 2 ) 3 C 4 H 5 O 4 , 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.