Second-order Nonlinear Optical Coefficients Research Articles

Boosted Second Harmonic Generation of a Chiral Hybrid Lead Halide Resonant to Charge Transfer Exciton from Metal Halide Octahedra to Ligand.

Chiral hybrid organic-inorganic metal halides (HOMHs) offer an ideal platform for the advancement of second-order nonlinear optical (NLO) materials owing to their inherent noncentrosymmetric structures. The enhancement of optical nonlinearity of chiral HOMHs could be achieved by matching the free exciton and/or self-trapped exciton energy levels with desired NLO frequencies. However, the current scarcity of resonance modes and low resonance ratio hamper the further improvements of NLO performance. Herein, we propose a new resonant channel of charge transfer (CT) excited states from metal halide polyhedra to organic ligand to boost the second-order optical nonlinearity of chiral HOMHs. The model lead halide (C7H10N)PbBr3 (C7H10N=1-ethylpyridinium) exhibits a drastically enhanced second harmonic generation in resonance to the deep CT exciton energy, with intensity of up to 111.0 times that of KDP and 10.9 times that of urea. The effective NLO coefficient has been determined to be as high as ~40.2 pm V-1, balanced with a large polarization ratio and high laser damage threshold. This work highlights the contribution of organic ligands in the construction of a resonant channel for enhancing second-order NLO coefficients of metal halides, and thus provides guidelines for designing new chiral HOMHs materials for advanced nonlinear photonic applications.

New Functional Groups Design toward High Performance Ultraviolet Nonlinear Optical Materials.

ConspectusThe invention of the laser is a pivotal milestone in the evolution of modern science and technology. Second-order nonlinear optical (NLO) crystals, which possess the ability to convert frequencies, have found widespread applications in laser science, information transmission, industrial Internet, and other cutting-edge fields within materials and optics. As modern science and technology continue to advance at a rapid pace, existing ultraviolet (UV) and deep ultraviolet (DUV) NLO crystals struggle to meet the ever-growing demands of various applications. Consequently, the development of novel UV and DUV NLO crystals has become an urgent necessity. For a UV NLO crystal to be considered outstanding in the UV/DUV range, it must exhibit three fundamental yet crucial properties: large second-order NLO coefficients, suitable birefringence, and short UV cutoff edge corresponding to a wide band gap. However, these key factors often conflict with one another, making it challenging to achieve a harmonious balance within a single crystal. It is widely believed that these mutually constrained optical properties are codetermined by microscopic NLO-active units and macroscopic structure features. Therefore, how to design high performance UV NLO-active groups to balance these three key properties is an essential scientifically question and serious challenge. In this Account, we present three strategies for designing high-performance UV NLO-active groups: (1) The "tetrahedron partial substitution" strategy by employing various substituents to replace one or more atoms in the traditional nonpolar tetrahedral groups, might achieve the aim of increasing the polarizability anisotropy and hyperpolarizability of the newly formed polar tetrahedral functional groups, such as from SO4 to SO3NH2 or SO3CH3 groups. (2) The "structure-analogue" strategy to develop a range of organic functional groups exhibiting more strong polarizability anisotropy and hyperpolarizability by using inorganic π-conjugated groups, such as BO3 and B3O6 groups, as templates. (3) The "two in one" strategy for integrating groups featuring planar triangle configurations and tetrahedrons to create NLO-active functional groups possessing large band gaps, strong hyperpolarizability, and moderate polarizability anisotropy. These three strategies successfully guide us to design and explore various kinds of organic-inorganic composite NLO crystal materials with excellent performances, like Ba(SO3CH3)2, M(SO3NH2)2 (M = Sr, Ba), C(NH2)3SO3F, KLi(HC3N3O3)·2H2O, KLi(C3H2O4)·H2O, and so on. Finally, we briefly conclude these strategies and propose some prospects for exploring new excellent UV/DUV NLO materials with practical applications. These findings could inspire novel thoughts for researchers designing new UV/DUV NLO materials and providing abundant materials used in UV/DUV regions.

Chiral Hybrid Germanium(II) Halide with Strong Nonlinear Chiroptical Properties.

Due to the pronounced anisotropic response to circularly polarized light, chiral hybrid organic-inorganic metal halides have been regarded as promising candidates for the application in nonlinear chiroptics, especially for the second-harmonic generation circular dichroism (SHG-CD) effect. However, designing novel lead-free chiral hybrid metal halides with large anisotropy factors and high laser-induced damage thresholds (LDT) of SHG-CD remains challenging. Herein, we develop the first chiral hybrid germanium halide, (R/S-NEA)3 Ge2 I7 ⋅H2 O (R/S-NGI), and systematically investigated its linear and nonlinear chiroptical properties. S-NGI and R-NGI exhibit large anisotropy factors (gSHG-CD ) of 0.45 and 0.48, respectively, along with a high LDT of 38.46 GW/cm2 ; these anisotropy factors were the highest values among the reported lead-free chiral hybrid metal halides. Moreover, the effective second-order nonlinear optical coefficient of S-NGI could reach up to 0.86 pm/V, which was 2.9 times higher than that of commercial Y-cut quartz. Our findings facilitate a new avenue toward lead-free chiral hybrid metal halides, and their implementation in nonlinear chiroptical applications.

π-Extended Octupolar Cyclized Indole Tetramer and Trimer Derivatives with Second- and Third-Order Nonlinear Optical Properties.

Several aromatic-fused octupolar tetraindole (TTI) and triindole (TI) derivatives have been synthesized via POCl3-promoted cyclopolymerization of the aromatic-fused oxindoles. As a result, the terminal phenyls of TTI and TI are fused with the phenyl group, indenyl group, and benzothienyl group separately in the π-extended target compounds TTIp and TIp, TTIid and TIid, and TTIbt and TIbt (including pairs of syn- and anti-isomers). Single-crystal X-ray diffraction disclosed that the tetramer syn-TTIbt keeps an S4-symmetric architecture and crystallizes in the P42/n space group. With the extension of the π-conjugation, the absorption and emission bands of the above tetramers and trimers are remarkably red-shifted. The second-order nonlinear optical (NLO) coefficients (β value) of syn-TTIbt and anti-TTIbt have been calculated to be 1.5 and 2.1 times that of their parent compound TTI, respectively. In the domain of the third-order NLO, the two-photon absorption sections (δ value) of syn-TIbt and anti-TIbt have been measured to be 37 and 102 times that of TI, respectively. These results indicate that the π-extension strategy here is successful, and the anti-isomers have better NLO properties and better π-conjugation than their corresponding syn-isomers.

Design Novel Chalcone Crystals for Enhancement of Nonlinear Optical Activity and Higher Molecular Structural Stability

In the design of molecular organic nonlinear optical (NLO) chalcone crystals, how to balance the stability of the crystal structure and the π-conjugation length while enhancing the NLO activity of the chromophore remains a challenge. In this study, we have synthesized a series of crystals 6MNPP (C20H16O2, Pca21), 6MN4TP (C21H18O2, Pca21), 6MN4EP (C22H20O2, Pca21), and 6MN3TP (C21H18O2, P21) by adding a benzene ring in D−π–A−π–D structure design and introducing new functional groups with large differences in electron-donating ability at both ends of the molecule. All four crystals are non-centrosymmetric structures, and the identification of NLO activity has been well demonstrated by analysis and characterization. Remarkably, 6MNPP crystals are competitive with similar NLO chalcone crystals, mainly including a higher second harmonic generation efficiency (9 × KDP) and higher melting point (Tm = 151.6 °C). Furthermore, first-principles calculations show that the second-order NLO coefficient d15 = 7.843 pm/V, at1064 nm. All the results suggest that 6MNPP crystals have significance potential in the NLO applications.

Local Polarity-Induced Assembly of Second-Order Nonlinear Optical Materials.

ConspectusSecond-order nonlinear optical (NLO) materials, producing coherent light by the cascaded frequency conversion, are current hot topics in material chemistry and optics, as they play an important role in diverse fields, such as laser technology, precision measurements, and quantum information as well as future space propulsion. The prerequisite for a second-order NLO material is that it must crystallize in a noncentrosymmetric space group, but it tends to be centrosymmetric in terms of thermodynamical stability. Furthermore, it should simultaneously satisfy strict requirements on second-order NLO coefficients, birefringence, optical transmittance windows, crystal growth, and so on. Therefore, it is still an urgent challenge to rationally assemble high-performance second-order NLO materials. In this Account, we first review the significance and background of second-order NLO materials and some strategies to design new second-order NLO materials controllably. After that, we mainly present our recent studies on the rational assembly of second-order NLO materials by the so-called strategy of "local polarity-induced assembly", including: (1) making use of the coordination habit between specific cations like Li+ or Mg2+ and tetrahedral (PO4)3-, (P2O7)4-, and (SO4)2- units to generate the local polarity, and further inducing the assembly of second-order NLO materials of superb optical properties; (2) by virtue of self-condensation of weakly polarizable units, condensation of different weakly polarizable units and partial substitution of O atoms by F or S atoms in weakly polarizable units of tetrahedral MO4 or octahedral MO6 configuration, enhancing the local polarity to induce the assembly of second-order NLO materials; and (3) introducing strongly polarizable units of stereoactive lone pair electrons into π-conjugated systems to afford the local polarity and inducing second-order NLO materials with enhanced NLO responses. Based on this strategy, we successfully assembled a variety of excellent second-order NLO materials and expanded new sources of second-order NLO materials, like fluorooxosilicophosphates, thiosulfates, and borosulfates. Finally, we will conclude the topic and give some prospects for exploring new excellent second-order NLO materials. We believe that the "local polarity-induced assembly" strategy will not only be useful for understanding the structure-property relationships of second-order NLO materials but also provide researchers with insights into obtaining noncentrosymmetric structures that are essential to other functional materials in piezoelectricity, ferroelectricity, and pyroelectricity, etc.

Second-order nonlinear optical coefficients of the monoclinic crystal BaGa4Se7.

We characterize the magnitude and relative signs of the second-order nonlinear optical coefficients of the biaxial crystal BaGa4Se7 (BGSe) combining measurements of phase-matched and non-phase-matched second-harmonic generation at different wavelengths using slabs and a sphere.

Impact of the Structural Modification of Diamondoid Cd(II) MOFs on the Nonlinear Optical Properties.

A change in the degree of interpenetration (DOI) in metal-organic frameworks (MOFs) prompted by heat, pressure, or exchange of solvents is a fascinating phenomenon that can potentially impact the functional properties of MOFs. Structural transformation involving two noncentrosymmetric MOFs with different DOIs provides a rare opportunity to manipulate their optical properties. Herein, we report an unusual single-crystal-to-single-crystal (SCSC) transformation of a noncentrosymmetric 7-fold interpenetrated diamondoid (dia) Cd(II) MOF into another noncentrosymmetric but 8-fold interpenetrated dia MOF upon the removal of guest solvents. A hydrogen-bond network formed between the lattice solvents and linker trans-2-(4-pyridyl)-4-vinylbenzoate (pvb) in a 7-fold interpenetrated noncentrosymmetric MOF results in a significant increase in the two-photon absorption cross-section (11 times) as compared to that in the desolvated 8-fold interpenetrated MOF. Also, an increase in the DOI in the noncentrosymmetric crystals strengthened the π···π interaction between the individual diamondoid networks and enhanced the second-order nonlinear optical (NLO) coefficient (deff) by 4.5 times. These results provide a way to manipulate the optical properties of MOFs using a combined strategy of the formation of hydrogen bonds and interpenetration for access to tunable single-crystal NLO devices in an SCSC manner. By changing the experimental conditions, another dia Cd(II) MOF with 4-fold interpenetration can be isolated. In this centrosymmetric MOF, the olefin groups in the backbone of the ligand (pvb) undergo a [2 + 2] cycloaddition reaction quantitatively under UV light but in a non-SCSC fashion.

Growth, ultraviolet‐visible, vibrational, photoluminescence and second harmonic generation studies of Amaranth and EDTA co‐doped KDP crystals

KDP (Potassium dihydrogen phosphate) single crystals were grown from Amaranth dye and EDTA (Ethylenediaminetetraacetic acid disodium salt) mixed KDP solutions by the temperature lowering method and Sankaranarayanan-Ramasamy technique. The molar concentration of EDTA in the solutions was 1 mol%. The Amaranth concentrations were 0.001, 0.005, 0.01, 0.03 and 0.05 mol%. The growth of KDP crystals was oriented in type I and type II phase-matching directions which bring maximum second harmonic generation (SHG) efficiency to the crystals. Optical properties of Amaranth and EDTA co-doped KDP crystals (KAE) were investigated by Ultraviolet-Visible (UV-Vis) spectroscopy, FT-Raman spectroscopy, and photoluminescence. SHG efficiency of the crystals was measured by shining 1064 nm Nd:YAG laser directly into them and receiving output signals. The most important result in the study showed that KAE crystals had SHG efficiency of 1.7 and 2.4 times higher than EDTA doped KDP crystal (KE) and pure KDP crystal respectively. Then second-order nonlinear optical coefficients of these crystals were calculated. The simultaneous doping of two organic substances into KDP crystals has further enhanced their nonlinear optical characteristics.

Nonlinear beam shaping in periodical χ (2) fork gratings with structural defects

Nonlinear beam shaping provides an efficient way to control the phase and amplitude of optical waves while shifting their frequency. Periodical topological structures with a modulated second-order nonlinear optical coefficient (χ (2)) are commonly used to generate special optical beams at new frequencies, e.g. the second harmonic vortices. In this paper, we theoretically study the influence of structural imperfection on nonlinear beam shaping and demonstrate how to utilize these imperfections for second harmonic generation with controlled orbital angular momentums. The results indicate that the studied nonlinear beam-shaping process has excellent tolerance to structural defects, and introducing designed defects of different scales and shapes constitutes a flexible approach for controlling the orbital angular momentum of light at new frequencies. As a proof of concept example, the nested χ (2) structures are designed for generating optical vortices with predesigned topological charges along different directions. In addition, the performance of the nonlinear generation of vortex beams with a fundamental beam shifted from the center of the fork grating is also discussed. The study opens up new prospects for the optimization of nonlinear χ (2) structures for special beam generation at new frequencies.

Tuning the optical properties of (TiO2)2 via the electric field

TiO2 nanomaterials have extreme applications in photocatalysis and photocell. The study of the properties of TiO2 clusters can provide meaningful references for further understanding of TiO2 nanomaterials. In this paper, tuning the optical properties of (TiO2)2 cluster was realized by applying an external electric field. The effect of the electric field on the IR spectra, energy gap, linear optical coefficient α and the second-order nonlinear optical coefficient β of (TiO2)2 cluster were concluded by density functional theory(DFT) method at B3LYP/6-311+G(d, p) basis set. The frequency shift and appearance of a new peak will happen in IR spectra with the fields. UV–vis absorption spectra were investigated using time-dependent density functional theory(TD-DFT) method. The absorption peak of the UV–vis absorption spectra redshift with the electric field increasing and a new absorption peak occurs in visible light range. Besides, the energy gap of (TiO2)2 cluster begins to decrease with the increase of the field. And the linear optical coefficient α and the second-order nonlinear optical coefficient β are found to increase. Especially, β rises particularly fast.

Characterization of all second-order nonlinear-optical coefficients of organic N-benzyl-2-methyl-4-nitroaniline crystal

Full elements of second-order nonlinear optical (NLO) tensor can be completely characterized for an organic NLO crystal for the first time. As-grown bulk N-benzyl-2-methyl-4-nitroaniline (BNA) crystal was processed to expose (100) and (010) crystal orientations with fine optical surfaces by using precision lathe and diamond blade. Then, every five nonvanishing second-order NLO coefficient of BNA can be determined quantitatively using the precisely processed crystals based on 1st-kind Maker fringe measurements. Our method makes it possible to clarify uncertain NLO property of any organic materials and to accelerate application study via precise device fabrications even for fragile organic materials.

First-principle study on structural, linear and nonlinear optical properties of selenocyanate complex ZnCd(SeCN)4 crystal

Bimetallic selenocyanate complex ZnCd(SeCN)4 (ZCSC) crystals are a novel material with ultraviolet nonlinear optical (NLO) properties. To the best of our knowledge, theoretical studies on these complexes have mostly focused on the microcosmic NLO responses of single complex molecular system and ignored their macroscopic NLO effects. In this paper, the geometric structure of ZCSC crystal was optimized on the basis of first principle, and the electronic band structure and linear optical (LO) properties were investigated via pseudopotential plane wave method. The macroscopic NLO properties of ZCSC crystal were evaluated through the combination of density functional theory and a devised anionic group method for the first time, and good agreement with the experimental results was obtained. The absorption spectrum of ZCSC was located at 95–325 nm, and the NLO properties were mainly caused by the transitions of electronic states from N2p and Se3p valence bands to C2p, N2p, Se3p, and Cd4p conduction bands. Results showed that the second-order NLO coefficients were d14 = 2.304–3.55 pm/V and d15 = 8.07–9.91 pm/V, showing an evident increase compared with those of ZnCd(SCN)4 crystals.

Targeting the Next Generation of Deep-Ultraviolet Nonlinear Optical Materials: Expanding from Borates to Borate Fluorides to Fluorooxoborates.

Coherent light radiation down to the deep-ultraviolet spectral range (λ < 200 nm) produced by common laser sources is extensively used in diverse fields ranging from ultrahigh-resolution photolithography to photochemical synthesis to high-precision microprocessing. Actually, it is hard to immediately obtain certain wavelengths, deep-ultraviolet coherent light in particular, from commercial laser sources. However, the direct second harmonic generation process governed in part by nonlinear optical crystals is a feasible and effective approach to generate deep-ultraviolet coherent light, which motivates chemists and materials scientists to find potential deep-ultraviolet nonlinear optical materials that can practically meet the scientific requirements. The research progress required to go from a new single-crystal structure to final device applications involves many pivotal steps and is highly time-consuming and challenging, and therefore, it is necessary to commence systematic studies aimed at shortening the research cycle and accelerating the rational design of deep-ultraviolet nonlinear optical materials. In this Account, we choose borates as raw materials because they have ever-greater possibilities to form desired noncentrosymmetric structures, wide optical transparency windows, rich structural chemistry, and also large polarizabilities to guarantee the coexistence of large second-order nonlinear optical coefficients and suitable birefringence. Besides, the effects of fluorine atoms on the structural chemistry and optical properties of borates have been summarized and analyzed. On the basis of these favorable influences, three specific rational design strategies, including experimental and theoretical methods, have been proposed in order to shorten the investigational cycle of discovering the new expected compounds with high physicochemical performances required for practical applications. In this way, the progress of searching for candidates for the next generation of deep-ultraviolet nonlinear optical materials was accelerated from borates to borate fluorides to fluorooxoborates with three effective strategies: (1) expansion of the frontier from borates to borate fluorides with the introduction of fluorine to achieve enhanced optical performance; (2) computer-assisted design of new deep-ultraviolet nonlinear optical materials with a newly introduced systematic global structure optimization method; and (3) expansion of the frontier from borate fluorides to fluorooxoborates by proposed functionalizedoxyfluoride [BO xF4- x]( x+1)- ( x = 1, 2, 3) chromophores to balance multiple criteria. The preliminary development of fluorooxoborates exhibiting high performance as a new fertile field to search for deep-ultraviolet nonlinear optical materials is highly encouraging and inspiring and can guide chemists and materials scientists with new directions and thoughts aimed at finding the next generation of practical deep-ultraviolet nonlinear optical materials.

Enhanced Second Harmonic Generation from Ferroelectric HfO2-Based Hybrid Metasurfaces.

Integrated nonlinear metasurfaces leading to high-efficiency optical second harmonic generation (SHG) are highly desirable for optical sensing, imaging, and quantum photonic systems. Compared to traditional metal-only metasurfaces, their hybrid counterparts, where a noncentrosymmetric nonlinear photonic material is incorporated in the near-field of a metasurface, can significantly boost SHG efficiency. However, it is difficult to integrate such devices on-chip due to material incompatibilities, thickness scaling challenges, and the narrow band gaps of nonlinear optical materials. Here, we demonstrate significantly enhanced SHG in on-chip integrated metasurfaces by using nanometer thin films of ferroelectric Y:HfO2. This material has the merit of CMOS compatibility, ultraviolet transparency up to 250 nm, and significant scalability down to sub-10 nm when deposited on silicon. We observe a 20-fold magnitude enhancement of the SHG intensity from the hybrid metasurface compared to a bare ferroelectric HfO2 thin film. Moreover, a 3-fold SHG enhancement is observed from the hybrid metasurface compared to a control structure using nonferroelectric HfO2, demonstrating a major contribution to the SHG signal from ferroelectric Y:HfO2. The effective second-order nonlinear optical coefficient χ(2) of Y:HfO2 is determined to be 6.0 ± 0.5 pm/V, which is comparable to other complex nonlinear photonic oxide materials. Our work provides a general pathway to build an efficient on-chip nanophotonic nonlinear light source for SHG using ferroelectric HfO2 thin films.

First-principles calculations of second-order nonlinear optical coefficients in the static limit and Pockels coefficients in III-N and II−IV−N2 compounds

The second-order nonlinear optical coefficients in the static limit are evaluated using density functional perturbation theory from the electronic response to a static electric field for the group-III nitrides and several $\mathrm{II}\text{\ensuremath{-}}\mathrm{IV}\text{\ensuremath{-}}{\mathrm{N}}_{2}$ ternary nitrides. They are compared with literature results using the sum over states approach including local field effects. The effects of the scissor correction are evaluated. Good agreement is obtained for GaN, AlN, and w-BN. For InN, the small or even negative gap in the LDA at $\mathrm{\ensuremath{\Gamma}}$ causes an extreme sensitivity to the k point summation and pseudopotentials. Similar problems occur for other very small gap $\mathrm{II}\text{\ensuremath{-}}\mathrm{IV}\text{\ensuremath{-}}{\mathrm{N}}_{2}$ semiconductors. The nonlinear optics coefficients are showing a general trend of increasing values with smaller gaps but no clear scaling relation with the direct gaps is obtained. In addition, unexpected changes in sign are found for the Si-based compounds, similar to the case of AlN, compared to the expected signs of ${d}_{33}$ in GaN. The Pockels coefficient, which includes in addition to the electronic response the phonon and piezoelectric response, is also evaluated. They show that the phonon and electronic contributions to the response in these materials are comparable in magnitude but in many cases of opposite sign.

Synthesis of Novel Chromophore Based on Tricyanocyclopentenone Acceptor and Its NLO Property

Novel organic second Nonlinear optical (NLO) chromophore GZP-T based on tricyanocyclopentenone electronic acceptor group were designed and synthesized in this paper. The structure of chromophore GZP-T is characterized by mass spectrum and nuclear magnetic resonance spectroscopy. And chromophore FTC based on traditional tricyanofuran electronic acceptor was also prepared as the contrast. Their delocalized energy levels were estimated by UV–VIS spectra. Their thermal properties were studied by thermogravimetric analysis (TGA). Obviously, chromophore GZP-T showed lower delocalized energy levels and higher thermal decomposition temperature (just about 290 °C). The poled films showed the largest second-order nonlinear optical coefficients of 103.1 and 68.6 pm/V, respectively, for chromophore GZP-T and FTC. These advantages of chromophore GZP-T are attributed to the improvement of first-order hyperpolarizability and the attenuatation of intermolecular dipole interaction by the introduction of tricyanocyclopentenone electronic acceptor. And in another word, tricyanocyclopentenone electronic acceptor may be a promising way to drastically change the nonlinear optical features of the titled compounds and show a direction of designing new electron acceptor in the field of nonlinear optical materials.

A Langbeinite-Type Yttrium Phosphate LiCs2Y2(PO4)3.

Langbeinite-type inorganic compounds have a wide range of applications, but nonlinear-optical properties are rarely mentioned in this series. Here, we report a new orthophosphate, LiCs2Y2(PO4)3, with a langbeinite-type structure, which is the first example in the system of mixed alkali-metal yttrium phosphates. Notably, LiCs2Y2(PO4)3 exhibits a moderate second-harmonic-generation efficiency of 0.9KH2PO4 and is transparent down to 200 nm. In addition, the thermal stability and theory calculations, including the electronic band structure, second-order nonlinear-optical coefficients, and dipole moment analysis, are also reported. This work not only expands the langbeinite-type system but also inspires a study on their nonlinear-optical properties.

Surface-step-terrace tuned second-order nonlinear optical coefficients of epitaxial ferroelectric BaTiO3 films

BaTiO3 films grown on SrTiO3 substrates with various miscut angles present different second-order nonlinear optical coefficients tuned by surface-step-terrace-induced strains.

A Cd(II) metal–organic framework based on semi-rigid ligand 3,5-(4-carboxybenzyloxy) benzoic acid with high stability by intramolecular hydrogen-bonding

A new metal–organic framework [Cd(HL)]n (FJU-15, H3L=3,5-(4-carboxybenzyloxy) benzoic acid) based on semi-rigid ligand was obtained, which exhibits high stability owing to intramolecular hydrogen-bonding interactions. FJU-15 remains intact in both boiling water and aqueous solutions with pH ranging from 1 to 12, a remarkably extensive pH range that a MOF can sustain. FJU-15 exhibits high thermal stability up to 380°C, weak second-order nonlinear optical coefficient as 0.31 times as that of potassium dihydrogen phosphate (KDP), and also displays a fluorescence emission band in the ultraviolet region.