Integration of Open Metal Sites in an Amino-Functionalized Sm(III)-Organic Framework toward Enhanced Third-Order Nonlinear Optical Property.

A variety of new inorganic and organic materials have emerged to advance laser technologies and optical engineering. A rational design approach can contribute significantly to fabricating nonlinear optically active metal-organic frameworks (MOFs) by considering the underlying structure-property linkage. Here, it has been embarked on a study of novel samarium(III) MOF, ([Sm2(ata)3(DMF)4]·DMF (ata2-: 2-aminoterephthalate), abbreviated as NH2-Sm-MUM-4) with enhanced nonlinear optical (NLO) properties. The crystal structure of this MOF represents a 6-connected framework with a pcu topology and distinctive characteristics, including open metal sites, free amine groups, and great stability, making it suitable for third-order NLO activity. The nonlinear index of refraction (n2) revealed the self-focusing impacts of NH2-Sm-MUM-4 at different incident intensities. The highest value of n2 and ß related to 10 mw power of incident intensity are 5.15 cm2/W and 2.65 cm/W, respectively. As far as the authors know, this is the first study examining the potential systematic structural-property associations in Sm-MOFs considering improved third-order NLO properties.

Bimetallic NiCo Metal-Organic Frameworks with High Stability and Performance Toward Electrocatalytic Oxidation of Urea in Seawater.

The urea oxidation reaction (UOR) is an alternative anodic reaction for hydrogen generation via water splitting. The significance of UOR lies in both H2 production and the decontamination of urea-containing wastewater. Commercial electrocatalysts in this field are generally based on noble metals and show several limitations. Bimetal-organic frameworks (BMOFs) can be excellent candidates for the replacement of noble-metal-based catalysts beacuse of their promising features, such as a tunable structure, high surface area, and abundant sites for electrocatalysis. In this study, a series of nickel-cobalt BMOFs (Nix-Coy-BMOFs: x and y refer to a molar fraction of Ni and Co) were synthesized and applied as electrocatalysts in UOR. In particular, a Ni0.15Co0.85-MOF material with a structure similar to that of its parent Co-MOF, revealed exceptional electrocatalytic performance, as evidenced by low values of overpotential (1.33 V vs RHE at 10 mA cm-2), TOF (0.47 s-1), and Tafel slope (125 mV dec-1). At a 40 mA cm-2 current density, Ni0.15Co0.85-MOF also showed excellent stability during the 72 h tests. This performance of NiCo-BMOF can be assigned to the synergistic effect between Co and Ni, abundant active sites, porosity, and a tunable structure, all of which result in an increased reaction rate due to the acceleration of charge and mass transfers. Thus, the present work introduces an efficient noble-metal-free UOR for energy generation from urea-based wastewater.

Water-Stable Pillared Three-Dimensional Zn-V Bimetal-Organic Framework for Promoted Electrocatalytic Urea Oxidation.

Urea oxidation reaction (UOR) is one of the potential routes in which urea-rich wastewater is used as a source of energy for hydrogen production. Metal-organic frameworks (MOFs) have promising applications in electrocatalytic processes, although there are still challenges in identifying the MOFs' molecular regulation and obtaining practical catalytic systems. The current study sought to synthesize [Zn6(IDC)4(OH)2(Hprz)2]n (Zn-MOF) with three symmetrically independent Zn(II) cations connected via linear N-donor piperazine (Hprz), rigid planar imidazole-4,5-dicarboxylate (IDC3-), and -OH ligands, revealing the 3,4T1 topology. The optimized noble-metal-free Zn0.33V0.66-MOF/NF electrocatalysts show higher robustness and performance compared to those of the parent Zn monometallic MOF/NF electrode and other bimetallic MOFs with different Zn-V molar ratios. The low potential of 1.42 V (vs RHE) at 50 mA cm-2 in 1.0 M KOH with 0.33 M urea required by the developed Zn0.33V0.66-MOF electrode makes its application in the UOR more feasible. The availability of more exposed active sites, ion diffusion path, and higher conductivity result from the distinctive configuration of the synthesized electrocatalyst, which is highly stable and capable of synergistic effects, consequently enhancing the desired reaction. The current research contributes to introducing a practical, cost-effective, and sustainable solution to decompose urea-rich wastewater and produce hydrogen.

Recent advanced strategies for bimetallenes toward electrocatalytic energy conversion reactions.

Designing low-dimensional nanomaterials is vital to address the energy and environmental crisis by means of electrocatalytic conversion reactions. Bimetallenes, as an emerging class of 2D materials, present promise for electrocatalytic conversion reactions. By leveraging atomically thin layers, bimetallenes present unsaturated surface coordination, high specific surface area and high conductivity, which are all indispensable features for heterogeneous electrochemical reactions. However, the intrinsic activity and stability of bimetallenes needs to be improved further for bimetallene electrocatalysts, due to the higher demands of practical applications. Recently, many strategies have been developed to optimize the chemical or electronic structure to accommodate transfer of reactants, adsorption or desorption of intermediates, and dissociation of products. Considering that most such work focuses on adjusting the structure, this review offers in-depth insight into recent representative strategies for optimizing bimetallene electrocatalysts, mainly including alloying, strain effects, ligand effects, defects and heteroatom doping. Moreover, by summarizing the performance of bimetallenes optimized using various strategies, we provide a means to understand structure-property relationships. In addition, future prospects and challenges are discussed for further development of bimetallene electrocatalysts.

Design and Advanced Manufacturing of NU-1000 Metal-Organic Frameworks with Future Perspectives for Environmental and Renewable Energy Applications.

Metal-organic frameworks (MOFs) represent a relatively new family of materials that attract lots of attention thanks to their unique features such as hierarchical porosity, active metal centers, versatility of linkers/metal nodes, and large surface area. Among the extended list of MOFs, Zr-based-MOFs demonstrate comparably superior chemical and thermal stabilities, making them ideal candidates for energy and environmental applications. As a Zr-MOF, NU-1000 is first synthesized at Northwestern University. A comprehensive review of various approaches to the synthesis of NU-1000 MOFs for obtaining unique surface properties (e.g., diverse surface morphologies, large surface area, and particular pore size distribution) and their applications in the catalysis (electro-, and photo-catalysis), CO2 reduction, batteries, hydrogen storage, gas storage/separation, and other environmental fields are presented. The review further outlines the current challenges in the development of NU-1000 MOFs and their derivatives in practical applications, revealing areas for future investigation.

Fluorinated Metal-Organic Frameworks with Dual-Functionalized Linkers to Enhance Photocatalytic H2 Evolution and High Water Adsorption.

Photocatalytic H2 evolution has recently attracted much attention due to the reduction of nonrenewable energy sources and the increasing demand for renewable sustainable energies. Meanwhile, metal-organic frameworks (MOFs) are emerging potential photocatalysts due to their structural adaptability, porous configuration, several active sites, and a wide range of performance. Nevertheless, there are still limitations in the photocatalytic H2 evolution reaction of MOFs with higher charge recombination rates. Herein, a copper-organic framework with dual-functionalized linkers {[Cu2(L)(H2O)2]·(5DMF)(4H2O)}n (fluorinated MOF(Cu)-NH2; H4L = 3,5-bis(2,4-dicarboxylic acid)-4-(trifluoromethyl)aniline) and with a rare 2-nodal 4,12-connected shp topology has been synthesized by a ligand-functionalization strategy and evaluated for the photocatalytic production of H2 to overcome this issue. According to the photocatalytic H2 evolution results, fluorinated MOF(Cu)-NH2 showed a hydrogen evolution rate of 63.64 mmol·g-1·h-1 exposed to light irradiation, indicating values 12 times that of the pure ligand when cocatalyst Pt and photosensitizer Rhodamine B were present. In addition, this MOF showed a maximum water absorption of 205 cm3·g-1. When dual-functionalized linkers are introduced to the structure of this MOF, its visible-light absorption increases considerably, which can be associated with nearly narrower energy band gaps (2.18 eV). More importantly, this MOF contributes to water absorption and electron collection and transport, acting as a bridge that helps to separate and transfer photogenerated charges while shortening the electron migration path because of the functional group in its configuration. The current paper seeks to shed light on the design of advanced visible-light photocatalysts with no MOF calcination for H2 photocatalytic production.

A Dual-Purpose Ce(III)-Organic Framework with Amine Groups and Open Metal Sites: Third-Order Nonlinear Optical Activity and Catalytic CO2 Fixation.

The present work focuses on the synthesis and properties of a novel multifunctional cerium(III) MOF, [Ce2(data)3(DMF)4]·DMF (data2-: 2,5-diaminoterephthalate), abbreviated as NH2-Ce-MUM-2. Its crystal structure reveals an intricate 3D 4,5-connected framework with a xah topology. This MOF features unique properties, such as open metal sites, presence of free amino groups, and high stability. Two main applications of NH2-Ce-MUM-2 were investigated: (i) as a heterogeneous catalyst in the CO2 fixation into cyclic carbonates and (ii) as a material with third-order nonlinear optical activity. As a model reaction, the cycloaddition of CO2 to propylene oxide to give the corresponding cyclic carbonate was explored under mild conditions, at the atmospheric pressure of carbon dioxide and in the absence of cocatalyst and added solvent. Various reaction parameters were investigated toward optimization and exploration of substrate scope, revealing up to 99% product yields of cyclic carbonate products. Besides, the structure of NH2-Ce-MUM-2 is highly stable, permitting its recyclability and reusability in further catalytic experiments. The significant contributions of free amino groups and open metal sites within this catalyst were particularly considered when proposing a potential mechanism for the reaction. Z-Scan measurements were used to evaluate the nonlinear optical (NLO) properties of NH2-Ce-MUM-2 at various laser intensities. A high two-photon absorption (TPA) under greater incident intensities shows that NH2-Ce-MUM-2 might be applicable in optical switching devices. Besides, the self-focusing effects of NH2-Ce-MUM-2 under various incident intensities were highlighted by the nonlinear index of refraction (n2). By reporting the synthesis and characterization of a novel MOF, along with its highly promising catalytic and NLO behavior, the current study introduces an additional example of multifunctional material into a growing family of metal-organic frameworks.

Water-Stable Fluorous Metal-Organic Frameworks with Open Metal Sites and Amine Groups for Efficient Urea Electrocatalytic Oxidation.

Urea oxidation reaction (UOR) is one of the promising alternative anodic reactions to water oxidation that has attracted extensive attention in green hydrogen production. The application of specifically designed electrocatalysts capable of declining energy consumption and environmental consequences is one of the major challenges in this field. Therefore, the goal is to achieve a resistant, low-cost, and environmentally friendly electrocatalyst. Herein, a water-stable fluorinated Cu(II) metalorganic framework (MOF) {[Cu2 (L)(H2 O)2 ]·(5DMF)(4H2 O)}n (Cu-FMOF-NH2 ; H4 L = 3,5-bis(2,4-dicarboxylic acid)-4-(trifluoromethyl)aniline) is developed utilizing an angular tetracarboxylic acid ligand that incorporates both trifluoromethyl (-CF3 ) and amine (-NH2 ) groups. The tailored structure of Cu-FMOF-NH2 where linkers are connected by fluoride bridges and surrounded by dicopper nodes reveals a 4,24T1 topology. When employed as electrocatalyst, Cu-FMOF-NH2 requires only 1.31 V versus reversible hydrogen electrode (RHE) to deliver 10 mA cm-2 current density in 1.0 m KOH with 0.33 m urea electrolyte and delivered an even higher current density (50 mA cm-2 ) at 1.47 V versus RHE. This performance is superior to several reported catalysts including commercial RuO2 catalyst with overpotential of 1.52 V versus RHE. This investigation opens new opportunities to develop and utilize pristine MOFs as a potential electrocatalyst for various catalytic reactions.

Metal-Organic Frameworks as Electrocatalysts.

Transition metal complexes are well-known homogeneous electrocatalysts. In this regard, metal-organic frameworks (MOFs) can be considered as an ensemble of transition metal complexes ordered in a periodic arrangement. In addition, MOFs have several additional positive structural features that make them suitable for electrocatalysis, including large surface area, high porosity, and high content of accessible transition metal with exchangeable coordination positions. The present review describes the current state in the use of MOFs as electrocatalysts, both as host of electroactive guests and their direct electrocatalytic activity, particularly in the case of bimetallic MOFs. The field of MOF-derived materials is purposely not covered, focusing on the direct use of MOFs or its composites as electrocatalysts. Special attention has been paid to present strategies to overcome their poor electrical conductivity and limited stability.

Pillared-MOF@NiV-LDH Composite as a Remarkable Electrocatalyst for Water Oxidation.

Oxygen evolution reaction (OER) represents a highly important electrochemical transformation in energy storage and conversion technologies. Considering the low rate of this four-electron half-reaction, there is a demand for efficient, stable, and noble-metal-free electrocatalysts to improve the kinetic and economical parameters. In this work, a new pillared-MOF@NiV-LDH nanocomposite based on a CoII metal-organic framework (pillared-MOF) and heterometallic Ni/V-layered double hydroxide (NiV-LDH) was assembled via a simple protocol, characterized, and explored as an electrocatalyst in OER. A remarkable electrocatalytic efficiency of pillared-MOF@NiV-LDH in 1 M KOH is evidenced by a low overpotential (238 mV at 10 mA cm-2 current density) and a small value of the Tafel slope (62 mV dec-1). These parameters are very close to those of the reference IrO2 electrocatalyst and are superior to the majority of the LDH- and MOF-based systems previously applied for OER. Excellent stability of pillared-MOF@NiV-LDH was confirmed by the chronopotentiometry tests for 70 h and linear-sweep voltammetry after 7000 cycles. Features such as rich electroactive sites, porous structure, high surface area, and synergic effect between pillared-MOF and NiV-LDH are likely responsible for the remarkable electrocatalytic efficiency of this electrocatalyst in OER. Despite prior reports on the application of NiV-LDH in OER, the present study describes the first example where this type of LDH is blended with MOF to generate a nanocomposite material. The interface between the two components of the composite can improve the electronic structure and, in turn, the electrocatalytic behavior. The introduction of this composite paves the way toward the synthesis of other multicomponent materials with potential applications in different energy fields.

Postsynthetic Modification of NU-1000 for Designing a Polyoxometalate-Containing Nanocomposite with Enhanced Third-Order Nonlinear Optical Performance.

For the advancement of laser technologies and optical engineering, various types of new inorganic and organic materials are emerging. Metal-organic frameworks (MOFs) reveal a promising use in nonlinear optics, given the presence of organic linkers, metal cluster nodes, and possible delocalization of π-electron systems. These properties can be further enhanced by the inclusion of solely inorganic materials such as polyoxometalates as prospective low-cost electron-acceptor species. In this study, a novel hybrid nanocomposite, namely, SiW12@NU-1000 composed of SiW12 (H4SiW12O40) and Zr-based MOF (NU-1000), was assembled, completely characterized, and thoroughly investigated in terms of its nonlinear optical (NLO) performance. The third-order NLO behavior of the developed system was assessed by Z-scan measurements using a 532 nm laser. The effect of two-photon absorption and self-focusing was significant in both NU-1000 and SiW12@NU-1000. Experimental studies suggested a much superior NLO performance of SiW12@NU-1000 if compared to that of NU-1000, which can be assigned to the charge-energy transfer between SiW12 and NU-1000. Negligible light scattering, good stability, and facile postsynthetic fabrication method can promote the applicability of the SiW12@NU-1000 nanocomposite for various optoelectronic purposes. This research may thus open new horizons to improve and enhance the NLO performance of MOF-based materials through π-electron delocalization and compositing metal-organic networks with inorganic molecules as electron acceptors, paving the way for the generation of novel types of hybrid materials for prospective NLO applications.

Mixed Metal Fe2Ni MIL-88B Metal-Organic Frameworks Decorated on Reduced Graphene Oxide as a Robust and Highly Efficient Electrocatalyst for Alkaline Water Oxidation.

The development of cost-effective and efficient oxygen evolution reaction (OER) catalysts has found increasing popularity due to the sluggish kinetics of OER, which has hampered the H2 production by H2O electrolysis. In this study, Fe2Ni MIL-88 (denoted FeNi) was composited by reduced graphene oxide (rGO, denoted R). Owing to the high porosity and abundant active sites of bimetallic MOF, proper conductivity of rGO, and the synergistic impact of Ni and Fe, the optimal composite (R@FeNi (1:1)) offered remarkable OER activity in alkaline environments. The obtained composite was employed in the OER, which led to a low overpotential of 264 mV at a current density of 10 mA cm-2 with a Tafel slope of 62 mV dec-1. Also, the bimetallic Fe2Ni MIL-88 nanorods grown on rGO led to a reduction in the onset potential of the OER. These findings exceeded the results of standard IrO2-based catalysts; they are also comparable or even better than the previously reported MOF-based catalysts.

Instantaneous Sonophotocatalytic Degradation of Tetracycline over NU-1000@ZnIn2S4 Core-Shell Nanorods as a Robust and Eco-friendly Catalyst.

The universal pollution of diverse water bodies and declined water quality represent very important environmental problems. The development of new and efficient photocatalytic water treatment systems based on the Z-scheme mechanisms can contribute to tackling such problems. This study reports the preparation, full characterization, and detailed sonophotocatalytic activity of a new series of hybrid NU@ZIS nanocomposites, which comprise a p-n heterojunction of 3D Zr(IV) metal-organic framework nanorods (NU-1000) and photoactive ZnIn2S4 (ZIS) nanostars. Among the obtained materials with varying content of ZIS (5, 10, 20, and 30%) on the surface of NU-1000, the NU@ZIS20 nanocomposite revealed an ultrahigh catalytic performance and recyclability in a quick visible-light-induced degradation of the tetracycline antibiotic in water under sonophotocatalytic conditions. Moreover, increased activity of NU@ZIS20 can be ascribed to the formation of a p-n heterojunction between NU-1000 and ZIS, and a synergistic effect of these components, leading to a high level of radical production, facilitating a Z-scheme charge carrier transfer and reducing the recombination of charge carriers. The radical trapping tests revealed that •OH, •O2-, and h+ are the major active species in the sonophotocatalytic degradation of tetracycline. Possible mechanism and mineralization pathways were introduced. Cytotoxicity of NU@ZIS20 and aquatic toxicity of water samples after tetracycline degradation were also assessed, showing good biocompatibility of the catalyst and efficacy of sonophotocatalytic protocols to produce water that does not affect the growth of bacteria. Finally, the obtained nanocomposites and developed photocatalytic processes can represent an interesting approach toward diverse environmental applications in water remediation and the elimination of other types of organic pollutants.

Simultaneous Presence of Open Metal Sites and Amine Groups on a 3D Dy(III)-Metal-Organic Framework Catalyst for Mild and Solvent-Free Conversion of CO2 to Cyclic Carbonates.

Carbon dioxide (CO2) fixation to generate chemicals and fuels is of high current importance, especially toward finding mild and efficient strategies for catalytic CO2 transformation to value added products. Herein, we report a novel Lewis acid-base bifunctional amine-functionalized dysprosium(III) metal-organic framework [Dy3(data)3·2DMF]·DMF (2,5-data: 2,5-diamino-terephthalate), NH2-TMU-73. This compound was fully characterized and its crystal structure reveals a 3D metal-organic framework (MOF) with micropores and free NH2 groups capable of promoting the chemical fixation of CO2 to cyclic carbonates. NH2-TMU-73 is built from the Dy(III) centers and data2- blocks, which are arranged into an intricate underlying net with a rare type of xah topology. After activation, NH2-TMU-73 and its terephthalate-based analogue (TMU-73) were applied for CO2-to-epoxide coupling reactions to produce cyclic carbonates. Important features of this catalytic process concern high efficiency and activity in the absence of cocatalyst, use of solvent-free medium, atmospheric CO2 pressure, and ambient temperature conditions. Also, NH2-TMU-73 features high structural stability and can be recycled and reused in subsequent catalytic tests. An important role of free amino groups and open metal sites in the MOF catalyst was highlighted when suggesting a possible reaction mechanism.

Metal-Organic Framework Derived Bimetallic Materials for Electrochemical Energy Storage.

Supercapacitors (SCs), showing excellent power density, long service life, and high reversibility, have received great attention because of the increasing demand for energy storage devices. To further improve their performance, it is essential to develop advanced electrode materials. One group of materials, porous crystalline solids referred to as metal-organic frameworks (MOFs), have proved to be excellent templates for synthesizing functional materials to be employed in the preparation of electrodes for SCs. In comparison to monometallic MOFs, bimetallic MOFs and their derivatives offer a number of advantages, including tunable electrochemical activity, high charge capacity, and improved electrical conductivity. This review focuses on the use of MOF-derived bimetallic materials in SCs, the origin of the improved performance, and the latest developments in the field. Furthermore, the challenges and perspectives in this research area are discussed.

Enhanced electrochemical oxygen and hydrogen evolution reactions using an NU-1000@NiMn-LDHS composite electrode in alkaline electrolyte.

A well-designed NU-1000@NiMn-LDHS (NU@LDHS) composite can offer efficient electrocatalytic performance with ultralow HER and OER overpotentials of 93 and 129 mV, respectively, at a current density of 10 mA cm-2 in 2 M KOH. Outstanding OER and HER activities of the composite could be attributed to the porosity and higher surface area of NU-1000 (NU), the layered structure of NiMn-LDHS (LDHS), abundant active sites in LDH, and synergistic interaction between NU and LDHS.

An Asymmetric Supercapacitor Based on a Non-Calcined 3D Pillared Cobalt(II) Metal-Organic Framework with Long Cyclic Stability.

In this work, a new 3D metal-organic framework (MOF) {[Co3(µ4-tpa)3(µ-dapz)(DMF)2]·2DMF}n (Co(II)-TMU-63; H2tpa = terephthalic acid, dapz = pyrazine-2,5-diamine, DMF = dimethylformamide) containing low-cost and readily available ligands was generated, fully characterized, and used as an electrode material in supercapacitors without the need for a calcination process. Thus, the synthesis of this material represents an economical and cost-effective method in the energy field. The crystal structure of Co(II)-TMU-63 is assembled from two types of organic building blocks (µ4-tpa2- and µ-dapz ligands), which arrange the cobalt nodes into a complex layer-pillared net with an unreported 4,4,4,6T14 topology. The presence of open sites in this MOF is promising for studying electrochemical activity and other types of applications. In fact, Co(II)-TMU-63 as a novel electrode material when comparing with pristine MOFs shows great cycling stability, large capacity, and high energy density and so acts as an excellent supercapacitor (384 F g-1 at 6 A g-1). In addition, there was a stable cycling performance (90% capacitance) following 6000 cycles at 12 A g-1 current density. Also, the Co(II)-TMU-63//activated carbon (AC) asymmetric supercapacitor acted in a broad potential window of 1.7 V (0-1.7 V), exhibiting a high performance with 4.42 kW kg-1 power density (PD) and 24.13 Whkg-1 energy density (ED). These results show that the pristine MOFs have great potential toward improving different high-performance electrochemical energy storage devices, without requiring the pyrolysis or calcination stages. Hence, such materials are very promising for future advancement of the energy field.

Dual-Purpose 3D Pillared Metal-Organic Framework with Excellent Properties for Catalysis of Oxidative Desulfurization and Energy Storage in Asymmetric Supercapacitor.

This study proposes an approach for improving catalysis of oxidative desulfurization (ODS) of diesel fuel under mild reaction conditions and enhancing supercapacitor (SC) properties for storage of a high amount of charge. Our approach takes advantage of a novel dual-purpose cobalt(II)-based metal-organic framework (MOF), [Co(2-ATA)2(4-bpdb)4] n (2-ATA: 2-aminoterephthalic acid and 4-bpdb: N, N-bis-pyridin-4-ylmethylene-hydrazine as the pillar spacer), which is called NH2-TMU-53. Due to the stability of the used compound, we decided to evaluate the capability of this compound as a novel electrode material for storing energy in supercapacitors, and also to investigate its catalytic capabilities. It is demonstrated that the addition of H2O2 as an oxidant enhances the efficiency of sulfur removal, which indicates that NH2-TMU-53 can efficiently catalyze the ODS reaction. According to the kinetics results, the catalyzed process follows pseudo-first-order kinetics and exhibits 15.57 kJ mol-1 activation energy. Moreover, with respect to the radical scavenging evaluations, the process is governed by direct catalytic oxidation rather than indirect oxidative attack of radicals. Furthermore, NH2-TMU-53 was applied as an electrode material for energy storage in SCs. This material is used in the three-electrode system and shows a specific capacitance of 325 F g-1 at 5 A g-1 current density. The asymmetric supercapacitor of NH2-TMU-53//activated carbon evaluates the further electrochemical activity in real applications, delivers the high power density (2.31 kW kg-1), high energy density (50.30 Wh kg-1), and long cycle life after 6000 cycles (90.7%). Also, the asymmetric supercapacitor practical application was demonstrated by a glowing red light-emitting diode and driving a mini-rotating motor. These results demonstrate that the fabricated device presents a good capacity for energy storage without pyrolyzing the MOF structures. These findings can guide the development of high-performance SCs toward a new direction to improve their practical applications and motivate application of MOFs without pyrolysis or calcination.

Ni-Ti Layered Double Hydroxide@Graphitic Carbon Nitride Nanosheet: A Novel Nanocomposite with High and Ultrafast Sonophotocatalytic Performance for Degradation of Antibiotics.

Pollution of water resources by antibiotics is a growing environmental concern. In this work, nanocomposites of g-C3N4@Ni-Ti layered double hydroxides (g-C3N4@Ni-Ti LDH NCs) with high surface areas were synthesized through an optimized hydrothermal method, in the presence of NH4F. Application of various characterization techniques unraveled that the prepared nanocomposites are composed of porous Ni-Ti LDH nanoparticles and hierarchical g-C3N4 nanosheets. Further, these NCs were employed for photocatalytic and sonophotocatalytic removal of amoxicillin (AMX), as a model antibiotic, from aqueous solutions. In addition, sonocatalysis was performed. It was found out that the g-C3N4@Ni-Ti LDH NCs outperform their pure g-C3N4 and Ni-Ti LDH components in photocatalytic degradation of AMX under visible light irradiation. Also, the following order was determined for efficiency of the three adopted processes: sonocatalysis < photocatalysis < sonophotocatalysis. Furthermore, variation of the sonophotocatalysis conditions specified 500 W light intensity, 9 s on/1 s off ultrasound pulse modem and 1.25 g/L g-C3N4-20@Ni-Ti LDH as the optimal conditions. In this way, optimization of the highly efficient sonophotocatalytic process resulted in 99.5% AMX degradation within 75 min. Moreover, a TOC analyzer was employed to estimate the rate of AMX degradation over the nanocomposites. In addition, formation of hydroxyl radicals (•OH) on the surface of the g-C3N4-20@Ni-Ti LDH particles was approved using the terephthalic acid probe in photoluminescence (PL) spectroscopy. No significant loss was observed in the sonophotocatalytic activity of the nanocomposites even after five consecutive runs. Also, a plausible mechanism was proposed for the sonophotocatalysis reaction. In general, our findings can be considered as a starting point for synthesis of other g-C3N4-based NCs and application of the resultant nanocomposites to environmental remediation.

Ultrasound-assisted synthesis of NiFe- layered double hydroxides as efficient electrode materials in supercapacitors.

Under ultrasound irradiation, NiFe-layered double hydroxide (NiFe-LDH) nanostructures with three molar ratios and three dissimilar reaction times were prepared. The powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the synthesized nanomaterials. Using a sonochemichal route, various morphologies of the NiFe-LDH nanostructures without any impurity and variations in the structure were produced. During the optimization process, it was found that sonication time and reagent concentration in a fixed irradiation frequency can affect the size and the morphology of the produced nanostructures. Under ultrasound irradiation, non-aggregated particles with uniform, spherical morphology were obtained with molar ratios of 4:1 (Ni:Fe) with 45 W at 180 min. The NiFe-LDH samples were observed to be supercapacitor under a 6 M KOH solution. When morphologically-controlled NiFe-LDH samples were used, the pseudo-capacitive behavior of the nanostructures was tuned. After 3 h of ultrasonic irradiation, the optimized sample (NiFe-LDH spherical nanostructures with 4:1 M ratio) had a high value of specific capacitance (168F g-1).