Cooperation of Three Chromophores Generates the Water‐Resistant Nitrate Nonlinear Optical Material Bi3TeO6OH(NO3)2

Nitrates have long been ignored for practical uses as nonlinear optical (NLO) materials because they are usually very easy to dissolve in water; despite this, the π‐conjugated [NO₃]⁻ is among the most desirable NLO‐active structural units. The cooperation of three structural chromophores, namely, Bi₃O₆OH short chains with 6s² lone pair electrons, distorted TeO₆ octahedra with d¹⁰ electrons, and π‐conjugated [NO₃]⁻ triangles, generates a new nitrate NLO material, Bi₃TeO₆OH(NO₃)₂, which exhibits an enhanced phase‐matchable NLO response of three times that of KH₂PO₄ (3×KH₂PO₄), exceeding those of most nitrate NLO materials. Remarkably, the new material did not show obvious weight loss and degeneration of NLO response after being dipped in de‐ionized water for 24 h, indicating that it is highly resistant to water. Theoretical calculations reveal that foreign water molecules cannot stably stay in the crystal lattice of Bi₃TeO₆OH(NO₃)₂. These findings highlight the introduction of diverse chromophores into the nitrate systems as an effective approach for developing practical nitrate NLO materials that are of high water‐resistance and good optical performance.