Qiang-Xin Wang

Bio: Qiang-Xin Wang is an academic researcher from Guangxi Normal University. The author has contributed to research in topics: Crystal structure & Isostructural. The author has an hindex of 3, co-authored 3 publications receiving 940 citations.

Rigid Pillars and Double Walls in a Porous Metal-Organic Framework: Single-Crystal to Single-Crystal, Controlled Uptake and Release of Iodine and Electrical Conductivity

Abstract: A highly stable pillared and double-walled zinc(II) metal-organic framework with regular nanochannels displays single-crystal to single-crystal transformation upon desolvation and a large quantity of iodine uptake, controlled release, and electrical conductivity elevation due to synergy between the iodine guests and the host framework.

Iodine Release and Recovery, Influence of Polyiodide Anions on Electrical Conductivity and Nonlinear Optical Activity in an Interdigitated and Interpenetrated Bipillared-Bilayer Metal–Organic Framework

Abstract: {[Cu6(pybz)8(OH)2]·I5–·I7–}n (1), obtained hydrothermally by using iodine molecules as a versatile precursor template, consists of a cationic framework with two types of zigzag channels, which segregate I5– and I7– anions. The framework exhibits the first observed bipillared-bilayer structure featuring both interdigitation and interpenetration. 1 displays high framework stability in both acidic (HCl) and alkaline (NaOH) solutions. 1 slowly releases iodine in dry methanol to give [Cu6(pybz)8(OH)2](I–)2·3.5CH3OH (1′) and partially recovers iodine from cyclohexane to form [Cu6(pybz)8(OH)2](I–)2·xI2 (1″). Differences of up to 100 times in electrical conductivity and of 4 times in nonlinear optical activity (NLO) have been measured between 1 and 1′. This compound is one of few displaying multifunctionality, electrical conductivity, NLO, and crystal–crystal stability upon release and recovery of iodine. It is also unique in the iodine release from polyiodide anions in a metal–organic framework.

Molecular Packing Variation of Crimpled 2D Layers and 3D Uncommon 65.8 Topology : Effect of Ligand on the Construction of Metal -Quinoline-6-carboxylate Polymers

Abstract: Four coordination polymers Ni(quin-6-c)2 (1), Zn2(quin-6-c)4 (2), Co2(quin-6-c)4 (3), and Zn(OH)(quin-6-c) (4) (quin-6-c = quinoline-6-carboxylate) have been synthesized by methods of hydrothermal reaction and their crystal structures determined. In the compound 1, quin-6-c ligands act as ditopic linkers bound to Ni atoms, resulting in the formation of an unusually wavelike 2D (4,4) net. The adjacent layers are stacked offset with respect to each other, in an ABAB fashion. Compounds 2 and 3 are isostructural and feature a unique 2D molecular network composed of crimpled double-line ribbons. The 2D layers stack in a rare, interesting ABCD pattern along the crystallographic c axis. Compound 4 forms a novel 3D framework based on uncommon “new” 65.8 topology, crystallizes in the acentric orthorhombic space group Pna21 and displays powder SHG intensity ca. 460 times in comparing with that of α-quartz. The [Zn(μ2-OH)]n helical chains connected to each other through unsymmetrical quin-6-c ligands in 4 have ensur...

Metal‐Organic Frameworks: A Rapidly Growing Class of Versatile Nanoporous Materials

Abstract: Metal-organic frameworks (MOFs) represent a new class of hybrid organic-inorganic supramolecular materials comprised of ordered networks formed from organic electron donor linkers and metal cations. They can exhibit extremely high surface areas, as well as tunable pore size and functionality, and can act as hosts for a variety of guest molecules. Since their discovery, MOFs have enjoyed extensive exploration, with applications ranging from gas storage to drug delivery to sensing. This review covers advances in the MOF field from the past three years, focusing on applications, including gas separation, catalysis, drug delivery, optical and electronic applications, and sensing. We also summarize recent work on methods for MOF synthesis and computational modeling.

Rational synthesis of noncentrosymmetric metal-organic frameworks for second-order nonlinear optics.

Abstract: The term nonlinear optics (NLO) was coined to describe the nonlinear relationship between dielectric polarization P and electric field E in optical media. NLO is a cornerstone of the emerging field of photonics, in which photons instead of electrons are used for signal transmission and processing. The vision of photonic signal transmission, processing, and storage has attracted a great deal of attention from both the engineering and the scientific communities because of its great impact in many of the existing and future information technologies. The first step toward realization of these revolutionary technologies is to develop tools to manipulate photons. For example, it is desirable to develop materials with the ability to alter the frequency of light, to amplify light signal, and to modulate light intensity or phase factors. NLO phenomena can be the key to achieving these important functions. One of the most common NLO behaviors is second-harmonic generation (SHG), in which a NLO material mediates the “adding-up” of two photons to form a new one with twice the frequency. The SHGphenomenonwas first demonstrated by Franken et al. in 1961. In their pioneering work, a laser beam with a wavelength of 694.2 nm was irradiated through a quartz crystal and an output ultraviolet radiation with a wavelength of 347.1 nm (double frequency) was detected. After this discovery, numerous nonlinear optical phenomena have been studied and a number of NLO-active materials have been developed. Second-harmonic generation can be quantitatively described by the second-order nonlinear optical susceptibility χ, a third-rank tensor with 27 components. The tensor elements are related to each other tomeet the requirements of both inherent and structural symmetries, which greatly reduces the number of independent components of the susceptibility tensor. Only crystals in noncentrosymmetric crystal classes can have nonvanishing χ. Moreover, for material crystallizing in the noncentrosymmetric 422, 622, and 432 crystal classes, the second-order NLO response might also vanish due to structural symmetry as well as Kleinman’s symmetry. Many inorganic compounds crystallize in noncentrosymmetric space groups and have been found to be SHG active. Some important examples are potassium dihydrogen phosphate (KDP = KH2PO4), lithium niobate (LiNbO3), and barium sodium niobate (Ba2NaNb5O15). 7 New inorganic compounds have been explored for NLO applications including but not limited to metal borates 12 and metal oxides. Recent structural studies on the inorganic systems have led to a better understanding of crystal growth/packing, paving the way for potentially manipulating their crystallization tendency to form noncentrosymmetric structures. Since the 1970s molecular NLO materials, including organic, organometallic, and inorganic complexes, have been of increasing interest to synthetic chemists. 19 The existing library of organic compounds was first screened, and the urea crystal has become a SHG standard because of its high SHG efficiency and usual availability. In a microscopic view, the second-order NLO susceptibility χ is related to the first hyperpolarizability β of a molecule. According to the classical two-level model, β is enhanced by a large transition moment and a large dipole moment difference between the ground and the charge transfer excited state. A donor acceptor type of molecule often possesses both a large transition moment and a large excited state dipole moment. As a result, most of the organic SHG chromophors belong to this category. However, most of the molecules with large β values also possess a large dipole moment, which induces formation of centrosymmetric assemblies of molecules due to dipole dipole interactions. One of the methods to avoid the centrosymmetric alignment of molecular dipoles is to trap them inside the channels of asymmetric porous host structures. 28 Other methods include formation of poled polymers in which the required asymmetry is imposed by the external electric field 35 and the Langmuir Blodgett (LB)

Electrically Conductive Metal-Organic Frameworks.

Abstract: Metal–organic frameworks (MOFs) are intrinsically porous extended solids formed by coordination bonding between organic ligands and metal ions or clusters. High electrical conductivity is rare in M...

Capture of Volatile Iodine, a Gaseous Fission Product, by Zeolitic Imidazolate Framework-8

Abstract: Here we present detailed structural evidence of captured molecular iodine (I(2)), a volatile gaseous fission product, within the metal-organic framework ZIF-8 [zeolitic imidazolate framework-8 or Zn(2-methylimidazolate)(2)]. There is worldwide interest in the effective capture and storage of radioiodine, as it is both produced from nuclear fuel reprocessing and also commonly released in nuclear reactor accidents. Insights from multiple complementary experimental and computational probes were combined to locate I(2) molecules crystallographically inside the sodalite cages of ZIF-8 and to understand the capture of I(2) via bonding with the framework. These structural tools included high-resolution synchrotron powder X-ray diffraction, pair distribution function analysis, and molecular modeling simulations. Additional tests indicated that extruded ZIF-8 pellets perform on par with ZIF-8 powder and are industrially suitable for I(2) capture.