Hierarchical Layered Double Hydroxide Research Articles

A karst-inspired hierarchical Mg/Al layered double hydroxide with a high entropy-driven process for interception and storage.

Karstification plays a crucial role in forming magnificent scenery, and storing oil, natural gas, mineral resources, and water. Through the inspiration of karstification, a hierarchical layered double hydroxide (LDH) with funnel-like and cave-like structures (called Karst-LDH) is formed by the dissolution of acrylic acid/water solution. Meanwhile, the results of transmission electron microscopy (TEM) and scanning electron microscopy (SEM) show that Karst-LDH has complicated and interconnected internal pipe networks. The actual maximum phosphate adsorption capacity of Karst-LDH reaches 126.38 mg g-1 due to the unique structures, protonation, ligand exchange, ion exchange, and hydrogen bonding, which is over ten times that of general LDH with a regular hexagonal structure. The results of isotherms and thermodynamics also indicate that Karst-LDH conforms to more heterogeneous and multilayer adsorption with a higher entropy-driven process. Karst-LDH exhibits good selectivity for chloride and nitrate ions. The change in the frontier orbital interaction between phosphate and different LDHs is a significant reason for quick macropore transmission, mesopore interception, and finally, phosphate storage in Karst-LDH. This work provides an efficient way for the design and fabrication of high adsorption performance materials with unique karst-type structures, which can be used for multiple fields potentially.

A hierarchical layered double hydroxide electrode with surface porous microstructured fibers for flexible and wearable energy storage

A novel strategy to fabricate the highly conductive NiCo–SSY@CPMs electrode on surface porous microstructured fibers with hierarchical structures and mechanical stability has been developed for flexible, wearable, and high-performance ASC devices.

Facile and rapid synthesis of hierarchical LDHs array by universal molten salt with bound water toward efficient oxygen evolution electrocatalysis

Layered double hydroxide (LDH) is a kind of intensive used and highly efficient electrocatalyst. However, the traditional ways to prepare LDHs are time-consuming and energy cost and the electrochemical properties need to be further improved. Herein, we verified that bound water could exist in the molten salt at a temperature over 190℃. Hence, we developed the molten salt with bound water method (MSBWM), manufacturing hierarchical LDHs one step in molten salt. The as-obtain LDHs exhibit more excellent oxygen evolution reaction (OER) performance than corresponding hydrothermal synthesized. Their morphology and electronic structure were analyzed and compared carefully, indicating the unique and excellent characteristics of electrocatalysts made by MSBWM. Especially, FeCoNi LDH only needs 218 mV overpotential to drive 10 mA cm−2 and negligible descent after 24 h stability test. The unique advantages and easy-to-meet preparation conditions promise the MSBWM flexible design and large-scale preparation of hierarchical (oxy)hydroxides as advanced electrocatalysts.

Metal-organic framework-mediated synthesis of hierarchical layered double hydroxide for high-efficiency enrichment of phosphopeptides

When applied as adsorbents for phosphopeptides enrichment, two-dimensional (2D) layered double hydroxides (LDHs) are usually limited by the disadvantages of buried affinity sites and reduced specific surface area. Multifarious exfoliation strategies have been implemented to compensate for these deficiencies, but tedious exfoliation process cannot meet the requirements of LDHs as high-efficiency adsorbents. Incorporating LDHs with three-dimensional (3D) template can avoid tedious exfoliation and produce hierarchical LDHs with large specific surface area and massive affinity sites. Herein, a hierarchical LDH (denoted as Fe3O4@ZIF-8@Zn–Ga LDH) was prepared by metal-organic framework (MOF)-mediated synthesis strategy, and a magnetic solid-phase extraction (MSPE) platform was constructed and employed for phosphopeptides enrichment with high efficiency. The unique 3D structure and abundant metal nodes of MOF provide 3D template and metal sources for in-situ nucleation and generation of LDH. Large specific surface area and massive exposed Zn and Ga endow Fe3O4@ZIF-8@Zn–Ga LDH with high enrichment efficiency toward phosphopeptides from complicated biological samples. With the aid of mass spectrometry (MS) techniques, we profiled endogenous or global phosphopeptides from human saliva and serum, which proved the practical application value of this material.

Hierarchical NiCo-LDH core/shell homostructural electrodes with MOF-derived shell for electrochemical energy storage

Constructing hierarchical structure is an effective strategy to boost the electrochemical performance of layered double hydroxide (LDH) materials, but the rational design of such delicate architectures is still challenging. Herein, a unique hierarchical core/shell homostructure with NiCo-LDH nanorods (NCNRs) as core and NiCo-LDH nanosheets (NCNSs) as shell is constructed via in-situ ZIF shell growth and subsequent ion exchange-coprecipitation process. Such novel hierarchical structure provides a large accessible surface area and more exposed electrochemical active sites. The in-situ growth and conversion process contribute to the formation of robust adhesion between the core and the shell, which could facilitate the effective charge and ion diffusion, as well as improve the mechanical stability. Benefiting from the unique structure, the NCNRs@NCNSs electrode exhibits a high capacitance of 2640.2 F g−1, along with the good rate performance and cyclic stability. Furthermore, the as-assembled asymmetric supercapacitor of NCNRs@NCNSs//AC device displays a high energy density of 22.81 Wh kg−1 at the power density of 374.95 W kg−1. This work demonstrates a new strategy for designing hierarchical LDH with core/shell structure as electrode materials for superior electrochemical energy storage.

A defect-rich layered double hydroxide nanofiber filter with solar-driven regeneration for wastewater treatment

The need for environmental technology treatment of contaminants of emerging concerns (CECs) is increasing as CECs lead to detrimental effects on human health and ecosystems. Herein, defect-rich layered double hydroxide (LDH) structured into a fibrous filter with a facile solar-driven regeneration function was fabricated for efficiently removing adsorbed CECs in wastewater. The physical and chemical interactions between the LDH filter and CECs are revealed. It is demonstrated that the introduction of unsaturated Cuδ+ sites (δ < 2) and creating oxygen vacancies represents an effective way for improving adsorbing activity of the defect-rich LDH host layer. Also, the nanofiber-particle friction coefficient of the hierarchical LDH filter affects the filtration efficiency as revealed by 3D modelling. The LDH filter is capable of filtrating sixteen types of CECs and shows the capability of photocatalytic degradation of adsorbed CECs, thus enabling filter regeneration. This work thus presents a new perspective into bottom-up design of adsorbent materials: from molecular interactions to shaping adsorbents into microscopic nanofibers and assembling these into macroscopic 3D adsorbent filters.

A class of novel luminescent layered double hydroxide nanotubes.

Herein, we report a class of novel lanthanide-doped self-supported layered double hydroxide (LDH) nanotubes featuring a combination of micro- and mesoporosity. The synthesis of the nanotubes has been achieved by a soft-templating strategy. Incorporation of La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+ or Tb3+ in the LDHs assisted the self-assembly of the double hydroxide layers onto the surface of Pluronic P-123 worm-like micelles, enabling the formation of the nanotubes. Removal of the micellar template provides accessibility to the mesopores, yielding a network of hollow cylindrical nanotubes with internal diameter of about 10 nm. An antenna molecule (benzene-1,3,5-tricarboxylate, BTC) is hosted in their 1-nanometre-wide micropores. Upon UV excitation, the nanotubes emit light in a set of wavelengths ranging from the ultraviolet to the infrared.

Retardation and self-repair of erosion pits by a two-stage barrier on bioactive-glass/layered double hydroxide coating of biomedical magnesium alloys

Magnesium alloys for orthopedic applications are mainly restricted by their rapid degradation and undesirable surface mineralization. A hierarchical layered double hydroxide (LDH)/bioactive-glass (Bg) coating was constructed via in-situ hydrothermal growth to obtain LDH-container layer on magnesium alloys, and then a sol-gel spin-coating method to cover an outer bioactive-glass layer. The ion-exchange capacity of LDH-container layer was studied by stimuli-triggered release experiment. The results show that alkaline environment is conducive to the ingestion of aggressive chlorides accompanied fluoride-releasing, and this ion-exchange process reached equilibrium after 40 h. Electrochemical corrosion tests manifested that the LDH-container layer delayed the corrosion onset, declined the corrosion current by two orders of magnitude and positively shifted the corrosion potential of 1.15 V. Furthermore, corrosion degradation and mineralization evolution in vitro revealed that a well-defined self-repairing effect and collaborative mineralization were obtained when the LDH-container pre-encapsulated with fluoride and coupled with bioactive-glass. Specifically, the self-repairing was achieved by a local re-deposition of the degradation products Mg2+ and dissolved Ca2+ with the displaced F− to form stable magnesium fluoride or fluorapatite in the erosion pits. This intelligent two-stage strategy, based on physical protective barrier and self-repairing the eroded pits by re-depositing of bone-like minerals, progressively retarded rapid degradation and simultaneously facilitated remineralization. The strategy described herein provides a versatile route for designing smart corrosion protection coatings or targeting drug delivery systems.

In Situ Cascade Derivation toward a Hierarchical Layered Double Hydroxide Magnetic Absorbent for High-Performance Protein Separation

Selective enrichment and purification of histidine (His)-rich protein from complex mixtures is vital to satisfy the requirements of proteomic and diagnostic applications, but it still remain a chal...

3D hierarchical layered double hydroxide/carbon spheres composite with hollow structure for high adsorption of dye

In this paper, a 3D hierarchical layered double hydroxide (LDH)/carbon sphere (CS) composite was prepared via self-assembly method. After calcination, the hollow structure with high surface area was formed due to removing the carbon core, meanwhile, LDH turned into layered double oxide (LDO) which exhibited superior anion adsorption capacity. The formation of the prepared material was confirmed and characterized, and the adsorption mechanism of the obtained material for different charge anionic dyes was further discussed in detail. Under the optimal conditions, the maximum adsorption capacities of the prepared materials for amaranth and Orange II were 638.634 and 849.674 mg/g, separately, which revealed that the materials can be applied into the effective adsorption of anionic dyes, especially those with less charges.

Morphology-Controlled Synthesis of Three-Dimensional Hierarchical Flowerlike Mg–Al Layered Double Hydroxides with Enhanced Catalytic Activity for Transesterification

With the aim of simultaneously achieving synthesis and morphology control of three-dimensional (3D) hierarchical layered double hydroxide (LDH) by more efficient and environmentally friendly method...

A dissolvable hierarchical layered double hydroxide templated from porous zeolitic imidazolate framework-67 for dispersive solid phase extraction of bisphenol A

This is the first time that the in situ preparation of advanced extraction media based on a hierarchical layered double hydroxide (HLDH).

Hierarchical layered double hydroxides with Ag nanoparticle modification for ethanol sensing

Layered double hydroxides (LDHs) have recently been revealed to be promising in gas sensor applications due to their compositional flexibility and unique 2D-interlayer channel for gas diffusion and adsorption. This work demonstrates highly porous hierarchical LDHs containing Mg2+ and Al3+ (MgAl-LDHs) for ethanol sensing at room temperature. These MgAl-LDHs, with unique flower-like hierarchical structure and mesoporous interlayer, were synthesized hydrothermally using sodium dodecyl sulfate as soft template as well as intercalating agent. Further modification by discrete Ag nanoparticles (NPs) was achieved via an environmentally friendly glucose-reduction method to improve the gas-sensing response of the LDH-based sensor. It is found that the hierarchical MgAl-LDHs show potential in sensing ethanol gas with rapid dynamic characteristics at room temperature; their response magnitude towards ethanol can be enhanced significantly by Ag NP modification. The gas-response value of the Ag-modified MgAl-LDH sensor is about twice that of pristine MgAl-LDH sensors, towards 5–200 ppm ethanol at room temperature. Meanwhile, rapid response-recovery characteristics are achieved, with response and recovery times shorter than 10 and 50 s, respectively. The satisfactory sensing performance and remarkable response enhancement by Ag NP modification are demonstrated in terms of the unique microstructure of the hierarchical MgAl-LDHs and a constructed conductive effect model of Ag functionalized LDHs.

In-situ immobilization and pyrolysis of metal-organic framework supported on biomorphic layered double hydroxides as highly active and stable heterogeneous catalyst

Abstract In recent years, the pyrolysis of metal-organic frameworks (MOFs) has been widely employed to prepare advanced heterogeneous catalysts. However, large size or agglomeration caused by pyrolysis severely limits the performance of the catalysts due to the high mass transfer resistance. In this work, MOF crystals (Cu-BTC) in-situ grown on the biomorphic hierarchical layered double hydroxides (LDHs) surface (ZnAl-LDH/Cu-BTC) and it as a pyrolytic precursor to prepare layered double oxides/metal (ZnAl-LDO/Cu) composite catalyst were reported. ZnAl-LDH support induced the uniform distribution of nano-sized Cu-BTC on the nanosheets surface, and this unique method mediated Cu-BTC precursor for the in-situ construction of highly stable Cu nanoparticles under a high-temperature H2 reduction. ZnAl-LDO/Cu exhibited excellent catalytic activity and stability for the reduction 4-nitrophenol (4-NP) in the presence of NaBH4, which could be recycled for fifteen successive cycles with a high reduction efficiency (over 93%). Meanwhile, the ZnAl-LDO/Cu demonstrated high catalytic efficiencies on rhodamine B, congo red, methyl orange and methylene blue dyes. Hence, the concept presented in this work can be further expanded to synthesis of other MOFs derived high-efficiency non-noble metal catalysts, which have a great potential as a cost-effective and environmentally-friendly reusable catalyst to replace noble metals catalyst in large scale catalytic application.

Oxidation catalyst obtained by the immobilization of layered double hydroxide/Mn(iii) porphyrin on monodispersed silica spheres.

Several functional hybrid materials have been reported as immobilized porphyrin derivatives in various organic and inorganic host materials (polymers, mineral clays, silica, etc.), with potential applications in various fields, such as photochemistry, electrochemistry and heterogeneous catalysis. Layered double hydroxides (LDHs), commonly known as hydrotalcite-like materials, have also been analyzed for use as supports for metallocomplexes. Recently, nanocomposite materials with a core-shell structure produced by combining two kinds of nanometer-size materials have received considerable attention, since the use of these materials is a promising strategy to prevent the aggregation and self-oxidation of molecules, reducing the catalytic activity. In this study, monodispersed hierarchical layered double hydroxides on silica spheres (LDH@SiO2) with core-shell structures were developed for metalloporphyrin immobilization and the materials were used as the oxidant catalysts of different substrates.

In-situ growth of hierarchical layered double hydroxide on polydopamine-encapsulated hollow Fe3O4 microspheres for efficient removal and recovery of U(VI)

With the increasing demand of nuclear power plant, the depleted uranium is inevitably emitted and causes environmental risk, hence it is crucial to develop new methods to efficiently eliminate uranium compounds from water. In this work, a bifunctional material core-shell-shell layered double hydroxide (LDH) decorated hollow magnetic polydopamine (MP) microspheres (defined as MPL) were synthesized and evaluated for the cleanup of uranium (VI) from aqueous solutions through specific adsorption. The experimental results showed that the adsorption was significantly affected by pH value rather than ionic strength, reflecting that the interaction was mainly governed by inner-sphere surface complexation owing to the multiple functional groups including imine, catechol, amine, and hydroxyl groups. The adsorption kinetics can be perfectly depicted by the pseudo-second-order model with high uptake percentage of 94.8%, which was superior to the previously reported materials. Interestingly, the maximum adsorption performance can be tuned by changing the thickness of polydopamine shell and the content of LDH, in the order of MP2L2 (344 mg/g) > MP2L3 (291 mg/g) > MP3L2 (245 mg/g) > MP2L1 (211 mg/g) > ML2 (142 mg/g) > MP1L2 (141 mg/g) > MP2 (71 mg/g) > Fe3O4 (34 mg/g) at 298.15 K and pH 5.0. The adsorption mechanism has been thoroughly investigated with techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), thermo-gravimetric analyses (TGA), Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). In summary, the bifunctional material could be applied as promising building block for the enrichment and recovery of uranium (VI) from aqueous solutions in environmental pollution cleanup.

Template-free fabrication of hierarchically meso/macroporous architecture of layered double hydroxide by dry gel conversion method

A new type of hierarchically porous architecture of Mg2+, Al3+-containing layered double hydroxide, with well defined mesoporous/macroporous structure, has been fabricated by dry gel conversion method without the need of a surfactant and organic solvent. Predefined amorphous aluminum hydroxide gel and anhydrous magnesium sulfate were used as Al and Mg precursor material, respectively, and aqueous ammonia as precipitating agent. The resulting self-sustaining hierarchical layered double hydroxide material exhibits a bi-modal porous structure having a macroporous network with macropore sizes of 100–200 nm and a well defined mesoporous structure of pore size around 3.9 nm in the macroporous framework. Layered double hydroxide crystallites are aligned with a multilayer manner to form the architecture structure. The formation process of layered double hydroxide architecture, such as the evolution of phase composition, pore structure, and particle morphology with reaction time was further verified and the formation mechanism is postulated.

Remarkable oxygen barrier films based on a layered double hydroxide/chitosan hierarchical structure

Organic–inorganic hybrid films are fabricated via an alternate assembly of a chitosan (CTS) polymer and hierarchical layered double hydroxide (H-LDH), which exhibit tremendous oxygen barrier properties with high stability as well as long-term maintenance.

Preparation and evaluation of a layered double hydroxide film on a nanoporous anodic aluminum oxide/aluminum wire as a highly thermal-resistant solid-phase microextraction fiber

A hierarchical layered double hydroxide framework on a nonporous anodic aluminum oxide/aluminum wire was used as a solid phase microextraction fiber for separation and determination of phenolic compounds.

Hierarchical construction of an ultrathin layered double hydroxide nanoarray for highly-efficient oxygen evolution reaction.

Efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) are essential components of renewable energy technologies, such as solar fuel synthesis and water splitting processes for powering fuel cells. Here, ultrathin NiCoFe layered double hydroxide (LDH) nanoplates, which directly grow on a cobalt-based nanowire array, forming a hierarchical nanoarray structure, are constructed as efficient oxygen evolution electrodes. In alkaline media, the ordered ultrathin hierarchical LDH nanoarray electrode shows dramatically increased catalytic activity compared to that of LDH nanoparticles and pure nanowire arrays due to the small size, large surface area, and high porosity of the NiCoFe LDH nanoarray. Only a small water oxidation overpotential (η) of 257 mV is needed for a current density of 80 mA cm(-2) with a Tafel slope of 53 mV per decade. The hierarchical LDH nanoarray also shows excellent structural stability in alkaline media. After continuous testing under a high OER current density (∼300 mA cm(-2)) for 10 h, the sample maintains the ordered hierarchical structure with no significant deactivation of the catalytic properties.