A new stable Zr-based MOP is successfully constructed. Unique cavity and 2D hydrogen-bonding networks endow the MOP with highly selective CO2 capture and excellent proton conduction.

Herein, we offer a simple but crucial case for rational design and syntheses of infrared nonlinear optical (NLO) materials by employing state-of-the-art AgGaS 2 as a parent model. On the basis of inheriting structural advantages of AgGaS 2 , an as-grown CuZnPS 4 crystal exhibits a sharply enlarged energy gap (3.0 eV) benefiting from the cosubstitution of Ag with lighter Cu/Zn. Remarkably, the valence electron distribution of CuZnPS 4 is optimized by bringing in cation vacancy defects, which significantly reinforce the second harmonic generation (SHG) (3 × AgGaS 2 ) and compensate for the adverse effect of band gap enlargement. Careful experimental and theoretical investigations illustrate that CuZnPS 4 strikes a desirable balance among a strong SHG response, good phase matchability, large band gap, high laser damage threshold, outstanding physicochemical stability, low melting point, and cost-effective but nontoxic composition, which might shed light on follow-up design and exploratory synthesis of NLO materials.

Highly polarizable mixed-anion structural building units (SBUs) have been demonstrated as promising candidates for high-performing optical crystals. In this work, two new mixedanion SBUs of [GeOSe 3 ] and [GeO 3 S] are first designed through partial isovalent substitution of chalcogen atoms by O atoms in the classical [GeQ 4 ] (Q = S, Se) tetrahedra. On the basis of these SBUs, two new quaternary oxychalcogenides, Sr 3 Ge 2 O 4 Se 3 and SrGe 2 O 3 S 2 , are successfully synthesized. Sr 3 Ge 2 O 4 Se 3 crystallizes in the noncentrosymmetric space group R3m and possesses unique zero-dimensional [Ge 2 O 4 Se 3 ] 6− units consisting of highly distorted [GeOSe 3 ] tetrahedra and [GeO 4 ] tetrahedra through a shared O atom. It displays intriguing potential as an infrared nonlinear optical material with a wide band gap (2.96 eV) and moderate second harmonic generation intensity (0.8 × AgGaS 2 ). SrGe 2 O 3 S 2 belongs to the centrosymmetric space group P2 1 /c and features 2∞[Ge 2 O 3 S 2 ] 2− layers formed by the corner-shared [GeO 3 S] tetrahedra. Moreover, the large birefringence of SrGe 2 O 3 S 2 (calculated Δn = 0.22−0.17 from 0.4 to 4.0 μm) gives it a potential as a birefringent material. Theoretical calculations revealed the crucial effects of mixed-anion [GeOSe 3 ] and [GeO 3 S] units on the moderate second harmonic generation response and large birefringence. The discovery of new mixed-anion SBUs of [GeOSe 3 ] and [GeO 3 S] will guide the exploration of new functional oxychalcogenides.

Four Hg-based IR nonlinear-optical materials, AHgSnQ4 (A = Sr, Ba; Q = S, Se), were discovered and investigated systematically. Their structures are built of two-dimensional [HgSnQ4]2– layers, which are assembled alternately by distorted (HgQ4 and SnQ4) tetrahedra and separated by eight-coordinated A2+ cations. The two sulfides AHgSnS4 (A = Ba, Sr) exhibit large second-harmonic-generation (SHG) responses (2.8 and 1.9 × AgGaS2 at 2.09 μm), as well as large band gaps (2.77 and 2.72 eV). The two selenides AHgSnSe4 (A = Ba, Sr) show even stronger SHG responses, about 5 times that of AgGaS2. Furthermore, all four compounds show phase-matching behavior, and the results of first-principles calculation elucidate the key role of the HgQ4 group in the enhanced SHG effect in β-BaHgSnS4 and BaHgSnSe4.

Trigonal-planar units with high physicochemical stability and large polarizability anisotropy are one kind of promising fundamental building block (FBB) for constructing novel nonlinear optical (NLO) materials. Though great achievements have been made in the ultraviolet/ deep ultraviolet (UV/DUV) region with trigonal-planar units, little attention has been paid to them in the infrared region owing to the lack of enough representatives. In this work, [AgSe 3 ] and [HgSe 3 ] are rationally proposed as NLO-active FBBs. In addition, Ag 6 HgMSe 6 (M = Si, Ge) have been screened out by combined density functional theory calculations and experiments as new types of IR NLO materials. Experiments demonstrate that both Ag 6 HgSiSe 6 and Ag 6 HgGeSe 6 show strong second harmonic generation (SHG) responses, valuable phase-matchable features, and congruent-melting thermal behaviors. Moreover, the great contributions of the trigonal-planar units are also discussed in detail.

Great enhancement of the second harmonic generation response is achieved in AgHgPS4 by introducing vacancy defects and highly distorted HgS4 tetrahedra using AgGaS2 as the template.

Two RE-based quaternary metal chalcogenides EuCdGeQ4 (Q = S, Se) are discovered. They possess many attractive properties as preferred IR NLO materials including large band gaps, phase-matched intense SHG and congruent melting behavior.

Chalcogenides with diamond-like (DL) structures are a treasury of infrared nonlinear optical (NLO) materials. Here, a ternary Hg-based chalcogenide with a defect DL structure, Hg 3 P 2 S 8 , is synthesized by solid-state reaction. Driven by the highly distorted [HgS 4 ] tetrahedra, this compound displays an interesting structural symmetry degradation from tetragonal to orthorhombic compared with its analogue Zn 3 P 2 S 8 . Meanwhile, the overall performances of Hg 3 P 2 S 8 are quite remarkable, including a very strong phase-matchable secondharmonic generation (SHG) response (4.2 × AgGaS 2 ), large band gap (2.77 eV), wide IR transparent range (0.45−16.7 μm), and high laserinduced damage threshold (4 × AGS). Furthermore, the theoretical analysis and local dipole moment calculations elucidate that the highly distorted [HgS 4 ] tetrahedra contribute a lot to the enhancement of the SHG effect. This discovery will motivate the exploration of other DL Hg-based chalcogenides serving as high-performing mid-IR NLO materials.