Inorganic Sheets Research Articles

The embedding of fluorescent N-methyl-9-acridone into a topological new layered aluminophosphate SYSU-2 by one-pot synthesis.

A layered aluminophosphate |C14H11NO|2[Al4(HPO4)4F4(H2O)2] (denoted as SYSU-2) with a new topology has been hydrothermally synthesized with N-methyl-9-acridone (NMA) as the organic structure-directing agent. Single-crystal X-ray diffraction analysis reveals that SYSU-2 crystallizes in a triclinic space group P1[combining macron], with the inorganic sheets stacked in an AA sequence. Hydrogen bonds are responsible for the neutral inorganic-organic layer connection. The layer structure of SYSU-2 is constructed by alternating AlO4F2 octahedra and PO4 tetrahedra. The topological analysis of SYSU-2 indicates an independent topology. The NMA layers are self-assembled with π-π interaction. SYSU-2 crystals show interesting dual-band emission fluorescence properties compared with NMA crystals. Under 406 nm UV irradiation, SYSU-2 crystals emit yellow light with two emission bands at 477 and 566 nm, while NMA crystals emit blue light with only one band at 473 nm. The differences may be derived from the difference of stacking orders and distance of NMA molecule layers between the two crystals.

Two Novel Catalysts Constituted by Transition Metal-Oxide-Based Cluster Cation Frameworks with Big Ellipse Cavities Accommodated with {PMo12O40} Cluster Anions for Multifunctional Catalytic Properties

Two novel hybrid compounds, [{Mo(NO3)2(2,2′-bpy)}0.5{Mo6O17(2,2′-bpy)6}][PMo12O40] (1); [{Mn(2,2′-bpy)2}0.5{Mo6O17(2,2′-bpy)6}][PMo12O40] (2) (bpy = 2,2′-bpyridine), have been synthesized under mild hydrothermal conditions and structurally characterized by physico-chemical and series of spectroscopic methods. Two rare compounds which are basically isostructural with similar cell parameters are composed of transition metal-oxide-based cluster cations (TMOC) and classical Keggin type {PMo12O40} anions. Both [{Mo(NO3)2(2,2′-bpy)}0.5{Mo6O17(2,2′-bpy)6}]n and [{Mn(2,2′-bpy)2}0.5{Mo6O17(2,2′-bpy)6}]n cluster cation fragments possess opened railway molybdenum-oxide-based infinite cation chains. Then through O⋯O bond interactions, the adjacent railway chains are linked together with inverse symmetry mode to generate two kinds of interesting 2D supramolecular positive layers accommodated with big ellipse {PMo12O40} anions. By H-bonding interactions, the alternative accumulations between layers and layers give rise to 3D supramolecular channel frameworks, and the {PMo12O40} anions from different layers each other also generate graphene-like negative inorganic sheets. The electrochemical behaviors and electrocatalytic activities of both compounds have been explored. The photocatalytic activities of compounds 1 and 2 for decomposition of rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) under UV irradiation also have been investigated. The catalytic performances for the tertbutyl hydroperoxide (TBHP) oxidation of styrene also were carried out. The results show that compounds 1 and 2 exhibit multifunctional catalytic performances.

Inorganic coordination polymer quantum sheets@graphene oxide composite photocatalysts: Performance and mechanism

Abstract

Reduced-Dimensional Perovskite Enabled by Organic Diamine for Efficient Photovoltaics.

Reduced-dimensional (RD) perovskite solar cells (PSCs) are emerging as highly attractive alternatives to three-dimensional (3D) PSCs due to their dramatically improved environmental stability and photostability. Diamine-based RD perovskites with a single organic amine interlayer possess orderly inorganic sheets and a smaller insulation area, indicating great potential in combining high efficiency and long-term stability. Here, we report an efficient and stable RD PSC based on 1,4-butanediamine (BDA). We found that the BDA-based RD perovskite exhibits improved crystallinity, reduced trap-state densities, and enhanced charge mobility compared to those of butylamine (BA)-based RD (BA-RD) perovskite. A high power conversion efficiency of 17.91% was achieved with negligible hysteresis. Moreover, the device showed improved stability compared to those of BA-RD and 3D films and devices. The findings may inspire new developments in introducing organic diamine for efficient and stable RD PSCs.

Atomic-Scale Tailoring of Organic Cation of Layered Ruddlesden-Popper Perovskite Compounds.

Layered Ruddlesden-Popper (RP) phase perovskite compounds have emerged as promising photovoltaic materials for solar cell applications, but they suffer from poor absorption and strong exciton-binding energy. Herein, fluoro-, chloro-, and bromo-substitutions on the 4-position of the phenyl group in the component C6H5CH2CH2NH3+ (PEA+) are designed and synthesized to investigate their effect on the layered RP type H-PEA2MA2Pb3I10 (MA = CH3NH3) perovskite as an example. Single-crystal X-ray diffraction and temperature-dependent photoluminescence spectroscopy characterization reveal the electron-withdrawing halogen in organic cations decreases the distortion of inorganic sheets and significantly reduces the impact of two-dimensional quantum and dielectric confinement. This is further verified with an increased visible absorption and lower exciton-binding energy for these new layered RP-type perovskite compounds. A planar structured perovskite solar cell using an F-PEA2MA2Pb3I10 layer achieves a power conversion efficiency of 5.8%, which is better than that of the reference H-PEA2MA2Pb3I10.

Fashioning Fluorous Organic Spacers for Tunable and Stable Layered Hybrid Perovskites

Two dimensional (2D) organic–inorganic hybrid perovskites have recently attracted enormous attention due to their higher environmental stability with respect to three-dimensional (3D) perovskites and larger structural tunability. The layered structure relaxes constraints on the dimensions of the organic cations that alternate the inorganic sheets, opening up a large choice on the organics, ultimately enabling the creation of tunable layered perovskites. Here, we report on a series of fluorous cations, varying in size and shape, as building blocks for a new family of fluorous 2D lead-iodide perovskites. These display a large tunability in the optical and dielectric properties depending on the structure of the fluorous cations. Importantly, despite the invariant inorganic framework, the 2D perovskite electronic structure is strongly affected by the cation size. The longer the cation, the smaller the 2D perovskite band gap and the exciton binding energy (reducing from 400 meV down to 130 meV). Such variation...

Donor/Acceptor Charge-Transfer States at Two-Dimensional Metal Halide Perovskite and Organic Semiconductor Interfaces

Metal halide perovskite semiconductors with small exciton binding energy have been widely used in perovskite solar cells and achieved rapid progress in terms of device performance. However, the strong excitonic nature of two-dimensional (2D) perovskites with small n values remains underexploited (n represents the number of inorganic monolayer sheets sandwiched between bulky organic cation layers). In this work, we report experimental evidence of donor/acceptor charge-transfer (CT) states formed at 2D metal halide perovskite/organic semiconductor heterojunctions, with a corresponding increase in photocurrent production for these excitonic materials. Furthermore, it is found that the size of the organic cation in the 2D perovskite layer plays a critical role in the CT process. The ability to dissociate excitons in 2D perovskites by interfacing with an organic semiconductor in a donor/acceptor configuration opens up new opportunities for exploiting the excitonic nature of low-dimensional perovskites in appli...

In-Situ Synthesis and High-Efficiency Photocatalytic Performance of Cu(I)/Cu(II) Inorganic Coordination Polymer Quantum Sheets.

Two-dimensional (2D) materials ultrathin quantum sheets have the advantage of elevating the catalysis performance and prominent edge effects, but most of them belong to element single valence materials. In this paper, the ultrathin Cu(I)/Cu(II) inorganic coordination polymer quantum sheet (ICPQS) {[CuII(H2O)4][CuI4(CN)6]} n is synthesized by controlling the appropriate molar ratio of raw material, reaction time, and temperature. Transmission electron microscopy (TEM) and atomic force microscope (AFM) analysis show that this ICPQS has a thickness of ∼0.2 nm. Due to the fact that about 58.16% of the Cu(I)/Cu(II) is occupied in molecular structure and most of the metal active sites are fully utilized, this ICPQS can accelerate the photocatalytic degradation of methylene blue (MB) (K = 2.5 mg·L-1·min-1 at pH 3) and organic compounds in coking wastewater and biotreated coking wastewater. Basing on mixed valences, the ICPQS can use visible light to promote energy transfer and increase quantum efficiency, paving the way for developing the next-generation monolayer 2D mixed valence photocatalysts.

A novel -Pb-O-Pb-Cu-Cl- inorganic layer-based pillared-layer framework: Synthesis, crystal structure and fluorescent property

A novel pillared-layer coordination polymer containing -Pb-O-Pb-Cu-Cl- inorganic sheets, [PbCuCl(3.5-pydc)]n (1) (3.5-H2pydc = pyridine-3,5-dicarboxylic acid), was obtained through the hydrothermal method. In compound 1, two symmetry-related Pb centers are bridged into a Pb2O2 dimer by two symmetrically carboxyl oxygen atoms from 3,5-pydc2− anions, each Pb2O2 dimer links four equivalent units into a 2D puckered Pb-O-Pb layer. Two symmetry-related Cu ions are bridged into a Cu2Cl2 dimer by two chlorine ions. Thus the -Pb-O-Pb- layer and Cu2Cl2 dimers are joined into a novel 2D puckered -Pb-O-Pb-Cu-Cl- inorganic layer. The 2D -Pb-O-Pb-Cu-Cl- inorganic layers are further pillared to form a 3D network through 3,5-pydc2− anions. To the best of our knowledge, the pillared-layer framework based on -Pb-O-Pb-Cu-Cl- inorganic layers has never been reported previously. Compound 1 exhibits weak blue light emission with the maximum at 383 nm upon excitation at 260 nm.

The Diversity of Layered Halide Perovskites

The two-dimensional congeners of the well-known three-dimensional perovskites display new properties enabled by their reduced dimensionality. Here, organic molecules separate inorganic sheets, affording the properties of both discrete molecules and extended solids in single, well-defined materials. The choice of organic and inorganic components engenders a large range of structural motifs, which yield diverse properties such as electroluminescence, white-light emission, photoconductivity, porosity, and reactivity. Layered halide perovskites have been known for decades. Their recent resurgence compels us to understand the fundamental studies that set the stage for their current technological relevance. We are not providing a comprehensive review of this vast and rapidly growing field. Instead, we highlight some of the discoveries that have directed current research in this field. We hope to introduce new researchers to layered halide perovskites to bring fresh perspectives to study this venerable family of materials that continue to surprise us today.

Out-of-plane polarization in a layered manganese chloride hybrid

We investigate possible mechanisms to induce electric polarization in layered organic-inorganic hybrids. Specifically, we investigate the structural phase transitions of PEA2MnCl4 (PEA = phenethylamine) using temperature dependent single-crystal X-ray diffraction analysis, including the symmetry analysis of the observed space groups. Our results show that PEA2MnCl4 transforms from a high-temperature centrosymmetric structure with space group I4/mmm to a low-temperature polar Pca21 phase via an intermediate phase with polar space group Aea2. We study the mechanism responsible for the I4/mmm to Aea2 polar phase transition and find that it is different from previously proposed mechanisms in similar systems. The transition is governed by the opening of a small dihedral angle between the phenyl ring planes of two adjacent PEA molecules, which consequently become crystallographically inequivalent in the Aea2 phase. This molecular rotation induces a significant difference in the lengths of the ethylammonium tails of the two molecules, which coordinate the inorganic layer asymmetrically and are consequently involved in different hydrogen bonding patterns. Consequently, the negatively charged chlorine octahedron that coordinates the Mn2+ cation deforms. This deformation moves the Mn2+ off-center along the out-of-plane-axis, contributing to the polar nature of the structure. Notably, the polar axis is out-of-plane with respect to the inorganic sheets. This is in contrast to other layered organic-inorganic hybrids as well as conventional layered perovskites, such as the Aurivillius phases, where in-plane polarization is observed. Our findings add to the understanding of possible mechanisms that can induce ferroelectric behavior in layered organic-inorganic hybrids.

Electrons, Excitons, and Phonons in Two-Dimensional Hybrid Perovskites: Connecting Structural, Optical, and Electronic Properties

Two-dimensional (2D) hybrid perovskites are stoichiometric compounds consisting of alternating inorganic metal-halide sheets and organoammonium cationic layers. This materials class is widely tailorable in composition, structure, and dimensionality and is providing an intriguing playground for the solid-state chemistry and physics communities to uncover structure-property relationships. In this Perspective, we describe semiconducting 2D perovskites containing lead and tin halide inorganic frameworks. In these 2D perovskites, charges are typically confined to the inorganic framework because of strong quantum and dielectric confinement effects, and exciton binding energies are many times greater than kT at room temperature. We describe the role of the heavy atoms in the inorganic framework; the geometry and chemistry of organic cations; and the "softness" of the organic-inorganic lattice on the electronic structure and dynamics of electrons, excitons, and phonons that govern the physical properties of these materials.

Ab Initio Design of Low Band Gap 2D Tin Organohalide Perovskites

Four layered hybrid perovskites, based on tin iodide sheets intercalated by divalent organic cations (ethylenediammonium, 2,2′-biaziridinium, 2,2′-biimidazolium, and 4,4′-bipyridinium), have been modeled with ab initio techniques. The crystal structures have been optimized at the DFT level, not including thermal effects, and finding and characterizing three minima for each cation; with respect to the analogues with monovalent cations, the structures are more distorted and mostly in a staggered arrangement. The interlayer distances are quite small for all of the systems, due to the single layer of strongly charged cations between the inorganic sheets. The band profiles and the band gaps, computed with an additive approach including the effects of spin orbit coupling and post-DFT correlation corrections, show an unexpected and interesting feature: with two of the cations some nearly degenerate low energy levels appear at the bottom of the conduction band. As a consequence, these systems present unusually lo...

Synthesis, X-ray diffraction and Hirshfeld surface analysis of two new hybrid dihydrate compounds: (C6H22N4)[SnCl6]Cl2·2H2O and (C8H24N4)[SnCl6]Cl2·2H2O.

Two new organic-inorganic hybrid compounds, tri-ethyl-ene-tetra-ammonium hexa-chlorido-stannate (IV) dichloride dihydrate, (C6H22N4)[SnCl6]Cl2·2H2O, (I), and 1,4-bis-(2-ammonio-eth-yl)piperazin-1,4-diium hexa-chlorido-stannate (IV) dichloride dihydrate, (C8H24N4)[SnCl6]Cl2·2H2O, (II), have been synthesized from the same starting materials. In each case both the cations and anions are located about inversion centers. Their crystal structures exhibits alternating inorganic and organic stacking sheets in (I) and layers in (II), with Cl- ions and water mol-ecules occupying the space in between. The cohesion of the three-dimensional frameworks are governed by N-H⋯Cl, N-H⋯O, C-H⋯Cl and O-H⋯Cl hydrogen bonds. Hirshfeld surface analysis of both crystal structures indicates that the H⋯Cl/Cl⋯H contacts exert an important influence on the stabilization of the packing.

A novel mixed-metal borate with large [B12O18(OH)6]6- motif: Synthesis, structure and property

A new mixed-metal polyborate, Na5Li[B12O18(OH)6]·2H2O (1), has been synthesized using solvothermal method and characterized by IR spectroscopy, thermogravimetric analysis, UV–Vis spectroscopy, powder and single-crystal X-ray diffraction, respectively. It crystallizes in the trigonal space group R-3c (No. 167) with unit cell parameters of a = b = 9.6767(6) Å, c = 36.358(5) Å, and Z = 6. Its structure features unprecedented 3D framework constructed from novel honeycomb-shaped inorganic Na-O sheets with unique 12-MR sodium rings and supramolecular polyborate 2D layers of lithium-centered [B12O18(OH)6]6-. UV–Vis spectral characterization indicates that compound 1 is a wide-band-gap semiconductor.

Two-dimensional vermiculite separator for lithium sulfur batteries

Lithium-sulfur batteries have been considered as one of the most promising battery system for their high theoretical energy density. However, the lithium-sulfur batteries suffer from the dissolution and diffusion of polysulfides, which induce parasitic reactions with lithium metal anodes. The safety of lithium-sulfur batteries is also concerned with the risk of dendrite growth on lithium metal anodes. To simultaneously address the challenges in the shuttle effect and safety problems, we demonstrate herein a two-dimensional vermiculite separator. With the assembly of the 2D exfoliated vermiculite sheets, the vermiculite separator can suppress the diffusion of polysulfides across the separator through electrostatic interaction and steric hindrance. Meanwhile, the inorganic sheets with high strength and Young’s modulus prevent the penetration of lithium metal dendrite and potentially improve the safety of the system. This work elucidates a promising strategy for safe and stable lithium sulfur batteries, and can also be extended to other electrochemical systems based on metal anodes.

Cationic two-dimensional sheets for an ultralight electrostatic polysulfide trap toward high-performance lithium-sulfur batteries

Lithium–sulfur batteries have many advantages, including their low material cost, high safety, and high energy density, and thus, they have recently been pursued as the most promising alternative to lithium-ion batteries in a multitude of applications, ranging from electric vehicles to stationary grid storage. However, these batteries are greatly hindered by certain problems, especially their low utilization of sulfur and fast capacity depletion due to the dissolution of the intermediate discharge product, polysulfide, and its diffusion across the separator to the anode side. In this study, we report the utilization of inorganic cationic sheets as a conformal modification layer on the separator, synergistically working as both a physical confinement barrier and chemical trap that efficiently blocked the crossover of polysulfide and accordingly improved the cycling life of Li–S batteries. Notably, due to the high percentage of surface atoms and the synergy of the physical and chemical trapping functions, the modification loading was minimized to a record low level (a density of ~0.018mgcm−2 and a thickness of 20–30nm), promising the unsacrificement of energy density when considering the entire cell. This proof-of-concept work of utilizing inorganic cationic sheets as a modification layer on a commercial separator provides a cheap and simple but effective strategy to enhance the cycle life of Li-S batteries.

Antioxidant intercalated hydrocalumite as multifunction nanofiller for Poly(propylene): Synthesis, thermal stability, light stability, and anti-migration property

One of the major issues for poly(propylene) PP concerns its protection towards oxidative phenomena resulting in polymer failure. Using known anti-oxidant (AO), Irganox 1425, an original approach is taking advantage of the counterion, cations Ca2+, in building hydrocalumite inorganic sheets, and concomitantly providing the AO anions to be immobilized within an inorganic host structure. Through the classical co-precipitation method, the hybrid assembly composed of AO molecules interleaved between hydrocalumite layered structure is successfully elaborated in one-step process free of contamination. Hydrocalumite (Ca2Al) belongs to the family of layered double hydroxides (LDH). The structure of the AO-LDH hybrid material is determined by means of XRD, FT-IR, while the radical-scavenging activity of AO-LDH is investigated using DPPH• (1,1-Diphenyl-2-picryl-hydrazyl) radical concentration variation. A series of AO-LDH/PP composites is then obtained by dispersing AO-LDH into PP at different loading ratios, and addressing the thermal stability, light stability and anti-migration of the resulting composites. The use of hydrocalumite vessel in confining AO molecules helps to increase the thermal stability and resistance against the photo oxidation while providing a barrier effect against organic species migration. An optimized of 4 wt% AO-LDH into PP results in the best radical-scavenging activity, 1 wt% is preferred to stabilize PP under light, the former formulation is the best compromise of all the series.

Control of the white-light emission in the mixed two-dimensional hybrid perovskites (C6H11NH3)2[PbBr4−xIx

The control of the composition of mixed organic-inorganic hybrid perovskites by solid-state alloying is a very efficient tool to tune the band gap of the material, leading to enhanced optical performances. At this end, we have elaborated a series of mixed-halide two-dimensional hybrid perovskites (C6H11NH3)2[PbBr4−xIx], with 0 ≤ x ≤ 4, for which we studied the composition-dependence of the structural parameters and their effect on the white-light luminescence properties at room temperature. The structural analysis revealed the existence of a composition-induced structural phase transition occurring in the range 2 < x < 2.4, associated to a change between Cmc21 and Pbca space groups. The optical properties, investigated using optical absorption and photoluminescence measurements, have shown that bromine (Br) to iodine (I) halogen ion substitution redshifts the excitonic optical absorption band, as a result of the hybridization of the valence band structure, built from np orbitals of Br and/or I halogens and 6s orbitals of lead. When iodine was predominant (x > 2), the photoluminescence spectra showed a sharp peak with a relatively small Stokes shift (less than 0.2 eV) attributed to free or bound excitons emissions. In contrast, when the bromide is majority (x < 2), the photoluminescence response consists in a broadband white-light emission with a very large Stokes shift (between 1.2 eV and 0.3 eV), attributed to self-trapped excitons activated by a strong structural distortion of the inorganic sheets. Confronting optical and structural data highlighted the effect of the structure in monitoring the optical properties, since the intensity of the white-light emission increases with the bromine content and was found to excellently correlate with the change of the angular distortion of inorganic octahedra PbX6 (X = I/Br).

Structural origins of broadband emission from layered Pb-Br hybrid perovskites.

Through structural and optical studies of a series of two-dimensional hybrid perovskites, we show that broadband emission upon near-ultraviolet excitation is common to (001) lead-bromide perovskites. Importantly, we find that the relative intensity of the broad emission correlates with increasing out-of-plane distortion of the Pb-(μ-Br)-Pb angle in the inorganic sheets. Temperature- and power-dependent photoluminescence data obtained on a representative (001) perovskite support an intrinsic origin to the broad emission from the bulk material, where photogenerated carriers cause excited-state lattice distortions mediated through electron-lattice coupling. In contrast, most inorganic phosphors contain extrinsic emissive dopants or emissive surface sites. The design rules established here could allow us to systematically optimize white-light emission from layered hybrid perovskites by fine-tuning the bulk crystal structure.