Engineered Integration of Diverse Functional Units Induces Multifunctionality in Malonate‐Borate Hybrids

Borate‐based hybrids offer an excellent platform for advanced materials design, yet integrating multiple functional units remains challenged by competing structural requirements. Here, we presented a rationally designed hybrid system that first achieves synergistic coupling between π‐conjugated malonate and polymerized boro‐oxygen units through precise coordination chemistry control. We synthesized eight new malonate‐borate hybrids comprising two structural types: series I ([B 3 O 7 (OH)]‐based) and series II ([H 3 BO 3 ]‐based). Starting from three centrosymmetric series I compounds, controlled variation of stoichiometry and reaction pathways yielded four non‐centrosymmetric series II hybrids and one centrosymmetric series II phase, enabling tailored structural symmetry. The series II system exhibits diverse functional properties across the material series, including a high birefringence (Δ n = 0.203@546 nm) with a short cutoff edge of 200 nm, strong second‐harmonic generation responses rivaling KH 2 PO 4 (KDP), and high ionic conductivity. This work establishes a new paradigm for functional crystal engineering by elucidating fundamental design principles for balancing competing property requirements through controlled structural evolution.