A novel 3D coordination polymer, Zn 2 (μ 2 -OH)(SIP)(DPP) (1), with mixed ligands of 5-sulfoisophthalate (SIP) and 1,3-di-4-pyridylpropane (DPP), has been hydrothermally synthesized and characterized. 1 contains an unusual 3D subnet with distorted (10,3)-d topology and left/right-handed helical channels. Second-harmonic-generation (SHG) measurements revealed that the material has a strong SHG response (∼2.5 times that of potassium dihydrogen phosphate (KDP)) and is phase-matchable. In addition, photoluminescent and thermogravimetric analysis were also performed on 1.The search for materials that possess crystallographic noncentrosymmetry (NCS) is of current interest and great importance because these materials can exhibit a variety of technologically important physical properties such as secondharmonic-generation (SHG), ferroelectricity, piezoelectricity, and pyroelectricity. 1,2 The most widely used such materials are inorganic oxide crystals based on octahedrally coordinated d 0 transition-metal ions such as Ti 4þ , V 5þ , Mo 6þ , and W 6þ , and lone-pair-containing Pb 2þ , Sb 3þ , Te 4þ , Se 4þ , and I 5þ cations due to both of them are susceptible to second-order Jahn-Teller distortions. 3-6 The combination of d 0 transitionmetal ions and lone-pair-containing cations in oxide materials can produce NCS structures with their inherent asymmetric coordination environments. 7 To date, much of the work on the synthesis of NCS materials has concentrated on the inorganic oxide solids. However, little attention has been paid to the NCS metal-organic coordination compounds that bear the advantages of the organic ligands and inorganic metal ions. Recently, Xiong et al. have done some pioneering work in this research field and demonstrated some useful strategies to assemble NCS coordination polymers through crystal engineering design. 2,8 The rational synthesis of crystallographic NCS materials, however, remains a great challenge. Of particular importance, the NCS coordination compounds commonly display no or small signals of related properties such as the SHG intensity and ferroelectricity. Herewith, we report on the synthesis and characterization of a novel three-dimensional (3D) zinc coordination polymer with a strong SHG response assembled from 5-sulfoisophthalic acid (H 3 SIP) and 1,3-di-4-pyridylpropane (DPP) ligands. Accurate SHG, photoluminescent, thermogravimetric analysis (TGA), and IR measurements on 1 were performed.The hydrothermal reaction of ZnO, NaH 2 SIP, DPP, and H 2 O at 160°C for 3 days afforded colorless crystals of 1, which is air-stable and insoluble in H 2 O and most common used organic solvents. The TGA curve ( Figure S1 in the Supporting Information) shows that the first weight loss occurs between 170 and 210°C, which corresponds to the release of the coordinated H 2 O molecule (weight loss: measured 2.77%; theoretical 2.96%). The sharp continual weight loss started at 370°C, corresponding to decomposition of the organic ligands. Its Fourier transform IR spectrum exhibits a strong O-H stretchi...