Guest water-controlled reversible crystalline-to-amorphous transition and concomitant fluorescence shift in a polar open coordination polymer

Electro-Induced Phase Transformation of a Conductive Metal-Organic Framework Film for Nonlinear Optical Switching

Achieving metal-organic frameworks (MOFs) with nonlinear optical (NLO) switching is profoundly important. Herein, the conductive MOFs Cu-TCNQ phase I (Ph-I) and phase II (Ph-II) films were prepared using the liquid-phase-epitaxial layer-by-layer spin-coating method and steam heating method, respectively. Electronic experiments showed that the Ph-II film could be changed into the Ph-I film under an applied electric field. The third-order NLO results revealed that the Ph-I film had a third-order nonlinear reverse saturation absorption (RSA) response and the Ph-II film displayed a third-order nonlinear saturation absorption (SA) response. With increases in the heating time and applied voltage, the third-order NLO response realized the reversible transition between SA and RSA. The theoretical calculations indicated that Ph-I possessed more interlayer charge transfer, resulting in a third-order nonlinear RSA response that was stronger than that of Ph-II. This work applies phase-transformed MOFs to third-order NLO switching and provides new insights into the nonlinear photoelectric applications of MOFs.

Crystal structure of poly[(μ2-1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene-κ2 N:N′)-(μ3-pyridazine-4,5-dicarboxylate-κ3 O:O′:N)]copper(II) hydrate, C19H16CuN6O5

C19H16CuN6O5, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 9.0143(3) Å, b = 9.2122(3) Å, c = 11.8205(4) Å, α = 82.900(3)°, β = 74.593(3)°, γ = 83.612(3), V = 935.90(5) Å3, Z = 2, R gt (F) = 0.0284, wR ref (F 2) = 0.0684, T = 293 K.

Three-Dimensional Metal-Free Molecular Perovskite with a Thermally Induced Switchable Dielectric Response

Temperature-responsive materials with switching physical properties have been widely researched. Among them, the switchable dielectric perovskite materials show potential applications in the electrical and electronic industries and even the intelligence industries. However, perovskite oxides and hybrid organic-inorganic perovskites, as the most representative switchable dielectric materials, are limited by bad biocompatibility. Herein, we report temperature-dielectric-responsive metal-free perovskite (H₂dabco)(NH₄)[BF₄]₃ constructed by the strategy of substituting the B site in the general formula ABX₃ (doubly protonated 1,4-diazabicyclo[2.2.2]octane = H₂dabco). Meanwhile, structurally similar hybrid material (H₂dabco)Rb[BF₄]₃ was designed as a control. They exhibit similar phase-transition characteristics and dielectric response behaviors around 333 K. More interestingly, the ordered-disordered transformation of their organic "spherical" cations (H₂dabco) was deemed to produce their phase transitions and dielectric response switching. Given its ability to generate a dielectric response, (H₂dabco)(NH₄)[BF₄]₃ will show the potential application of metal-free perovskite in a future thermal sensing device.

Reversible Phase Transition of Porous Coordination Polymers

Porous coordination polymers or metal-organic frameworks with reversible phase-transition behavior possess some attractive properties, and can respond to external stimuli, including physical and chemical stimuli, in a dynamic fashion. Their phase transitions can be triggered by adsorption/desorption of guest molecules, temperature changes, high pressure, light irradiation, and electric fields; these mainly include two types of transitions: crystal-amorphous and crystal-crystal transitions. These types of porous coordination polymers have received much attention because of their interesting properties and potential applications. Herein, reversible phase transition porous coordination polymers are summarized and classified based on different stimuli sources. Corresponding typical examples are then introduced. Finally, examples of their applications in gas separation, chemical sensors, guest molecule encapsulation, and energy storage are also presented.

Crystal structure of diaqua-catena-poly[diaqua-bis(μ2-5-(4-(1H-1,2,4-triazol-1-yl)phenyl)tetrazol-2-ido-κ2 N:N′)cobalt(II)] dihydrate, C20H24CoN14O4

C20H24CoN14O4, triclinic, P1̅ (no. 2), a = 7.797(2) Å, b = 8.766(3) Å, c = 9.709(3) Å, α = 73.554(7)°, β = 86.460(7)°, γ = 78.537(7)°, V = 623.7(3) Å3, Z = 1, R gt(F) = 0.0303, wR ref(F 2) = 0.0752, T = 293(2) K.

Crystal structure poly-(μ2-1-(4-(1H-imidazol-1-yl)benzyl)-1H-1,2,4-triazolyl-κ2 N N 1:N 2 N)-(μ3-2,2′-(1,2-phenylene)diacetato-κ5-O 1,O 2:O 2:O 3,O 4)cadmium(II), C22H19CdN5O4

C22H19CdN5O4, monoclinic, P21/c, a = 11.7546(16) Å, b = 19.769(3) Å, c = 9.5012(13) Å, β = 106.252(2)°, V = 2119.6(5) Å3, Z = 4, R gt(F) = 0.0348, wR ref(F 2) = 0.0814, T = 296(2) K.