Hydroxy Double Salt Research Articles

Homogeneously Mixed Cu-Co Bimetallic Catalyst Derived from Hydroxy Double Salt for Industrial-Level High-Rate Nitrate-to-Ammonia Electrosynthesis.

Electrocatalytic nitrate reduction reaction (NO3RR) presents an innovative approach for sustainable NH3 production. However, selective NH3 production is hindered by the multiple intermediates involved in the NO3RR process and the competitive hydrogen evolution reaction. Hence, the development of highly efficient NO3RR catalysts is paramount. Herein, we report highly efficient bimetallic catalysts derived from hydroxy double salt (HDS). Under NO3RR conditions, Cu1Co1-HDS undergoes in situ reconstruction, forming nanocomposites of homogeneously distributed metallic Cu0 and Co(OH)2. Reconstruction-induced Cu0 rapidly converts NO3- to NO2-, which is further hydrogenated to NH3 by Co(OH)2. Homogeneously mixed Cu and Co species maximize this synergistic effect, achieving outstanding NO3RR performance including the highest NH3 yield rate (4.625 mmol h-1 cm-2) reported for powder-type NO3RR catalysts. Integration of Cu1Co1-HDS with a commercial Si solar cell attained 4.53% solar-to-ammonia efficiency from industrial wastewater-level concentrations of NO3- (2000 ppm), demonstrating practical application potential for solar-driven NH3 production. This study provides a strategy for enhancing the NH3 yield rate by optimizing the compositions and distributions of Cu and Co.

ZSM-5@MOF-199 core-shell composite adsorbent: Rapid ambient synthesis and CO/CO2 adsorption

Using a hydroxy double salt intermediate, we demonstrated rapid room temperature fabrication of ZSM-5@MOF-199 core–shell sorbents. Copper chloride was compatible with the ZnO-assisted MOF growth scheme. The structural and chemical properties of the composite were fine-tuned through either the core or the shell modification, targeting a superior adsorption capacity for CO and CO2 compared to parent adsorbents. For example, the Na2S2O3-assisted MOF-199 shell reduction enriched surface Cu+ and enhanced CO adsorption capacity. Modulating the zeolite core to protonic hierarchical ZSM-5 (HZSM-5) increased CO and CO2 uptake by 20 % and 28 %, respectively. The isosteric heat of adsorption revealed that the HZSM-5 core altered surface electronic properties and influenced the CO2 adsorption performance. Thermodynamic analysis indicated that the adsorption processes involved a combination of physisorption and electrostatic interactions with an ordered arrangement of adsorbates. The core–shell sorbent can be easily tuned for selective separation of CO and CO2.

Double Hydroxyl Salt as Smart Biocompatible pH-Responsive Carrier for 6-Mercaptopurine

Hydroxy double salts are layered materials that are considered to be biocompatible. For this reason, research has been initiated on the possibility of their use in drug delivery. Despite their use for several types of drugs, their potential for controlled release of mercaptopurine (MERC) has not been studied. In this work, the synthesized hydroxy double salt (HDS) material was used as a carrier for this drug for the first time. The effectiveness of HDS synthesis has been proven by such techniques as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Based on the FT-IR and energy-dispersive X-ray spectroscopy (EDS) results, the effectiveness of drug sorption was proven. The exact amount of drug retained was determined by the UV-Vis technique. The obtained results indicate that the drug is evenly distributed on the surface of the carrier, which is important during the controlled delivery of drugs. In the most important stage of the research, the effectiveness of drug release in response to changes in the pH of the environment was proven. The drug is not released into an environment that mimics healthy human tissues. It is released only after contact with the acidic environment that usually surrounds cancer cells. The low cellular toxicity of HDS and significant cytotoxic effect of HDS-MERC were confirmed by in vitro studies on MCF-7 human breast and DU145 prostate cancer cell lines and non-cancerous keratinocytes HaCaT. Interestingly, coupling with the HDS carrier increased the cytotoxic effect of MERC towards DU145 cells. Such an “intelligent” drug carrier for mercaptopurine has not been previously described in the literature. The obtained results indicate its great potential.

Eggshell-Derived Copper Calcium Hydroxy Double Salts and Their Activity for Treatment of Highly Polluted Wastewater.

By using methyl orange (MO) removal as a model reaction, the best temperatures for processing eggshells are 750 °C and above to obtain biobased CaO materials, a raw material for producing CuCa hydroxy double salt (HDS) materials with high efficiency in treatments of highly polluted wastewater (the initial concentration of MO is 500 ppm). Characterization techniques employed in this study include power X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, nitrogen adsorption-desorption analysis, and the colorimetric method, as well as energy-dispersive X-ray, infrared-, and electron spin resonance spectroscopies. Complete MO removal and high chemical oxygen demand (COD) efficiencies (>90%) can be achieved after 3 min treatments of the aqueous MO with the calcined eggshell-derived CuCa HDS materials. The spent, deactivated HDS materials can be regenerated by an acid wash method. The activity of CuCa HDS materials in MO removal is unaffected by eggshell sources, implying that sorting steps may be unnecessary when eggshell food waste (duck, quail, and hen eggshells) is collected to produce biobased CaO. The findings of this study demonstrated that eggshells can be used in place of limestone and could be a more sustainable, renewable, and cost-effective source for material development and other applications.

Confinement of gold nanoclusters on hydroxy double salt for versatile fluorescent sensing of bio-enzymes

Fluorescent gold nanoclusters (AuNCs) have generated significant research interest because of their fascinating physicochemical properties. However, their biosensing applications are limited by the relatively low quantum yield (QY). Herein, a simple confinement effect based on AuNCs as guest molecules and Zn-containing hydroxy double salt (HDS) as host material (AuNCs@HDS) was used to significantly improve the fluorescence properties of AuNCs. The QY increased from 1.24 % to 22.80 %, and the time-tedious preparation or purification procedures were avoided. Further, the validated excellent fluorescence properties of AuNCs enabled the construction of a versatile fluorescent sensing strategy for bio-enzymes for the first time. The p-nitrophenol (pNP), a product of many bio-enzymes-catalyzed hydrolyzes of pNP-substrate, can effectively quench the fluorescence of AuNCs@HDS through an inner filter effect (IFE) process. Therefore, the AuNCs@HDS successfully detected several enzymatic disease biomarkers with robust analysis capabilities by varying the pNP-substrate, including alkaline phosphatase (ALP), β-glucosidase (β-GLU) and β-galactosidase (β-GAL). This study will inspire the design of highly fluorescent AuNCs as tools for biosensing.

Selective adsorption of acetylene over carbon dioxide on glycine functionalized HKUST-1 with enhanced moisture stability

HKUST-1 is one of the most widely studied Metal-Organic Frameworks and is known for strong acetylene adsorption performance. However, it suffers from poor stability and lower working capacity after moisture exposure. To address this issue, we comparatively apply pristine HKUST-1 and glycine functionalized HKUST-1. They were prepared by a well-known low energy-consuming hydroxy double salt method. The ultrafast synthetic method was applied to obtain HKUST-1-ultrafast (HKUST-1-UF) and one glycine per three Cu sites was added HKUST-1 (HKUST-1-UF-GLY0.3). An adsorption study of C2H2 on the HKUST-1-UF and HKUST-1-UF-GLY0.3 shows that the introduction of glycine as the secondary binding unit increased the C2H2 uptake performance compared to that of bare HKUST-1. An evaluation of stability against moisture exhibits that the structural stability of HKUST-1-UF-GLY0.3 is enhanced compared to HKUST-1-UF. Further, in a breakthrough experiment using an equimolar C2H2/CO2 gas mixture, HKUST-1-UF-GLY0.3 exhibits a longer breakthrough time compared to HKUST-1-UF after thermal pre-treatment, or even pre-humidifying (RH 60% and RH 80%) overnight. The adsorbents can be repeatedly used as a C2H2 adsorbent over CO2.

Pre-programed hydroxy double salt templates for room-temperature controlled synthesis of mixed-metal zeolitic imidazolate frameworks

Bimetallic hydroxy double salts pre-programed through co-precipitation were found as excellent templates for mixed-metal MOFs.

Centimeter-Scale Pillared-Layer Metal-Organic Framework Thin Films Mediated by Hydroxy Double Salt Intermediates for CO2 Sensor Applications.

Fabrication of metal-organic framework (MOF) thin films over macroscopic surface areas is a subject of great interest for gas sensor application platforms such as optics and microelectronics. However, a direct synthesis of MOF films at ambient conditions, in particular pillared-layer MOF films due to their anisotropic structures, remains a significant challenge. Herein, we demonstrate for the first time a facile construction of dense and continuous pillared-layer MOF thin films on a centimeter scale via an aluminum-doped zinc oxide template and hydroxy double salt (HDS) intermediates at room temperature. A series of Cu(II)-based pillared MOFs with different 1,4-benzenedicarboxylic acid (bdc) ligands were explored for optimizing MOF film formation for CO2 sensor applications. Nonpolar ligands with lower water solubility preferentially formed crystalline pillared MOF structures from HDS intermediates. A Cu2(ndc)2(dabco) (ndc = 1,4-naphthalene-bdc; dabco = 1,4-diazabicyclo[2.2.2]octane) MOF demonstrated the most dense and uniform film growth with micrometer thickness over one square centimeter area. This synthetic approach for growing Cu2(ndc)2(dabco) MOF thin films was successfully translated toward two sensing platforms: a quartz crystal microbalance and an optical fiber sensor. These Cu2(ndc)2(dabco) MOF-coated sensors displayed sensitivity toward CO2 and response/recovery time on the scale of seconds, even at moderate humidity levels. This work provides a road map for producing continuous and anisotropic crystalline MOF thin films over a centimeter scale area on various substrates, which will greatly facilitate their utilization in MOF-based sensor devices, among other applications.

Green synthesis of hierarchically porous Cu- and Zn-MOFs by the combined action of hydroxy double salt and surfactant: An ultrafast method

Hierarchically porous MOFs have raised considerable interest recently, due to their variety potential applications in adsorption, separation of molecules, drug delivery, catalysis etc. Presence of mesopores (2–50 nm) along with micropores (<2 nm) in the MOF networks enable them to be used as hosts to accommodate molecules, which enable their reaction or transformation. Even though a number of approaches were explored recently to generate cavities in MOFs resulting in hierarchically structured materials, most of the methods require harsh experimental conditions and tedious down-stream treatments which are energy consuming, having potential risk of pollution and low production rate. In this work we report a simple, green and ultrafast route for the synthesis of two HP-MOFs (Cu-BDC MOF and Zn-BDC MOF) using the cooperative template strategy by the simultaneous introduction of ZnO as the accelerator and cetyltrimethylammonium bromide (CTAB) as the surfactant. ZnO was employed to accelerate the construction of the framework by the formation of hydroxy double salt (HDS) layers whereas CTAB was introduced as surfactant for the formation of template micelles which guide the formation of micro- and mesopores through a synergistic effect with the HDS. The advantage of this method is that the synthetic procedure was accomplished in a few minutes (6 min) at room temperature and pressure and this ultrafast synthetic approach provide a new route of synthesizing hierarchically porous MOFs with high space-time yields (STYs).

Anchoring copper nanoclusters to Zn-containing hydroxy double salt: construction of 2D surface confinement induced enhanced emission toward bio-enzyme sensing and light-emitting diode fabrication.

Surface CIEE based on Zn-HDS as host material and GSH-CuNCs as guest molecules was developed to produce fluorescence composite GSH-CuNCs/Zn-HDS for the first time. It displays high quantum yield, long fluorescence lifetime and good stability, and was applied to sensitive bioenzyme sensing and fabrication of a high performance light-emitting diode.

Polyol intercalation in copper substituted zinc hydroxide acetate and evaluation of its adsorptive role towards Congo red dye

The extent of incorporation of Cu2+for Zn2+ in layered zinc hydroxide acetate to convert it to a hydroxy double salt carried out following titrimetric experiments with KOH solution. The reflections present in the powder X-ray diffraction pattern became broad suggestive of incorporation of copper for zinc. Well defined weight-loss steps, in the thermogravimetric trace of zinc hydroxide acetate, became diffused with the inclusion of copper. The intercalation of various polyols (ethylene glycol, diethylene glycol, and propylene glycol)was performed successfully, exploiting the organophilic character of ZnCu hydroxide acetate. The interlayer spacing expanded for polyol intercalated samples, as indicated by their powder X-ray diffraction patterns.The FT-IR and Raman spectra of polyol intercalated samples confirmed their presence in the interlayer, and the samples showed enhancement in thermal stability. These samples showed mesoporosity and reasonably high surface area (128.6 m2/g). The role of ethylene glycol intercalated ZnCu hydroxy double salt as an adsorbent to remove harmful and carcinogenic CR dye molecules from aqueous solutions investigated. The physisorption process was majorly responsible for the effective removal of CR dye, following a pseudo-second-order kinetics.

Intercalation of glycine into hydroxy double salt and its adsorption performance towards Uranium(VI)

Abstract Human activities and natural processes lead to environmental water pollution by Uranium. In the field of environmental remediation, much attention has been paid to the development of an efficient adsorbent for removing uranyl ion (UO 2 2 + ) from contaminated water. In this work, a new material was synthesized by intercalation of glycine (Gly) into zinc containing hydroxy double salt (Zn5-NO3), and its adsorption properties towards uranyl ion were studied in an aqueous solution. The X-ray diffraction (XRD) analysis of the composite material (Zn5-Gly) indicated that Gly was inserted into the gallery of Zn5-NO3 with bilayer arrangement. The adsorption capacity of Zn5-Gly towards UO 2 2 + in an aqueous solution is 745.53 mg/g and removal rate close to 100%, these criteria make it a potential candidate for uranium removal. The adsorbent decreased 233.38 ppm of UO 2 2 + to 23.47 ppm inside 120 min and finally to 0.79 ppm within 7 h. The adsorption kinetics of UO 2 2 + fits with the pseudo-second-order model, suggesting a chemisorption mechanism mainly via amino and carboxyl groups interactions. The adsorption of UO 2 2 + by the adsorbent was confirmed by XRD, Fourier-transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS).

Water-Stable Chemical-Protective Textiles via Euhedral Surface-Oriented 2D Cu-TCPP Metal-Organic Frameworks.

Abatement of chemical hazards using adsorptive metal-organic frameworks (MOFs) attracts substantial attention, but material stability and crystal integration into functional systems remain key challenges. Herein, water-stable, polymer fiber surface-oriented M-TCPP [M = Cu, Zn, and Co; H2 TCPP = 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin] 2D MOF crystals are fabricated using a facile hydroxy double salt (HDS) solid-source conversion strategy. For the first time, Cu-TCPP is formed from a solid source and confirmed to be highly adsorptive for NH3 and 2-chloroethyl ethyl sulfide (CEES), a blistering agent simulant, in humid (80% relative humidity (RH)) conditions. Moreover, the solid HDS source is found as a unique new approach to control MOF thin-film crystal orientation, thereby facilitating radially arranged MOF crystals on fibers. On a per unit mass of MOF basis in humid conditions, the MOF/fiber composite enhances NH3 adsorptive capacity by a factor of 3 compared to conventionally prepared MOF powders. The synthesis route extends to other MOF/fiber composite systems, therefore providing a new route for chemically protective materials.

Templated fabrication of hierarchically porous metal-organic frameworks and simulation of crystal growth.

Hierarchically porous metal–organic frameworks (MOFs) have recently emerged as a novel crystalline hybrid material with tunable porosity. Many efforts have been made to develop hierarchically porous MOFs, yet their low-energy fabrication remains a challenge and the underlying mechanism is still unknown. In this study, the rapid fabrication of two hierarchically porous MOFs (Cu-BTC and ZIF-8) was carried out at room temperature and ambient pressure for 10 min using a novel surfactant as the template in a (Cu, Zn) hydroxy double salt (HDS) solution, where the (Cu, Zn) HDS accelerated the nucleation of crystals and the anionic surfactants served as templates to fabricate mesopores and macropores. The growth mechanism of hierarchically porous MOFs was analyzed via mesodynamics (MesoDyn) simulation, and then the synthetic mechanism of hierarchically porous MOFs at the molecular level was obtained. The as-synthesized hierarchically porous Cu-BTC showed a high uptake capacity of 646 mg g−1, which is about 25% higher as compared with microporous Cu-BTC (516 mg g−1) for the capture of toluene. This study provides a theoretical basis for the large-scale fabrication of hierarchically porous MOFs and offers a reference for the understanding of their synthetic mechanism.

Green and rapid preparation of hierarchically porous metal–organic zeolites and simulation of their growth

A green method to synthesize hierarchically porous metal–organic zeolites using a template strategy in a hydroxy double salt solution.

Rapid room temperature conversion of hydroxy double salt to MOF-505 for CO2 capture

Given the fact that solvothermal synthesis is the most common synthetic method to obtain metal–organic frameworks (MOFs) on a gram scale, it still remains a great challenge to produce MOFs in a scalable and sustainable synthetic process.

Hierarchically Porous Metal–Organic Frameworks: Green Synthesis and High Space-Time Yield

Two major goals of hierarchically porous metal–organic frameworks (HP-MOFs) research are the reduction of energy consumption and the enhancement of production rate. Here, we develop a simple and versatile method for the rapid synthesis of three HP-MOFs (Cu-BTC, Cu-BDC, and ZIF-8) through introducing zinc oxide (ZnO) and template simultaneously. The synthesis condition was facile, and the synthesis time could be shortened to 30 min. Moreover, the porosity and morphology of HP-MOFs could be adjustable with variable amounts and types of template. A synergistic effect of the hydroxy double salt (HDS) and template is crucial for the synthesis, whereas no meso- and macropores were formed in the individual employing of either the HDS or the template. The rapid synthesis mechanism was further elucidated by the mesoscopic dynamics simulation. Furthermore, the synthetic approach of HP-MOFs was readily scalable with a space-time yield (STY) of up to 1322 kg·m–3·d–1, which allowed the large-scale production. The prep...

Rapid, Selective, Ambient Growth and Optimization of Copper Benzene-1,3,5-Tricarboxylate (Cu–BTC) Metal–Organic Framework Thin Films on a Conductive Metal Oxide

Metal–organic frameworks (MOFs) are useful for thin film-based device integration as they show high adsorption capacity for selected gases. However, optimized device integration of MOFs for various platforms requires high-quality, well controlled thin film growth techniques that are flexible, scalable, and manufacturable. For this reason, there is a critical need for the ability to grow MOFs in the form of dense and uniform thin films efficiently on a wide range of substrates. In this work, copper benzene-1,3,5-tricarboxylate (Cu–BTC) MOF thin films are rapidly produced at room temperature by using a conductive aluminum-doped zinc oxide (AZO) as a seed layer to template Cu–BTC growth, with growth only occurring on the AZO layer via a hydroxy double salt intermediate. The formation pathway of the Cu–BTC films was investigated in detail because of the significant importance of improving the Cu–BTC film growth from the perspective of optimized device integration. We demonstrate that the structure of the resu...

ZnO Nanorod-Induced Heteroepitaxial Growth of SOD Type Co-Based Zeolitic Imidazolate Framework Membranes for H2 Separation.

Up to now, the fabrication of well-intergrown Co-based zeolitic imidazolate framework (ZIF) membranes on porous tubular supports is still a major challenge. We report here a heteroepitaxial growth for preparing well-intergrown Co-based ZIFs (ZIF-67 and ZIF-9) tubular membranes with high performance and excellent thermal stability by employing a thin layer of ZnO nanorods acting as both nucleation centers and anchor sites for the growth of metal-organic framework membranes. The results show that well-intergrown Co-ZIF-67 and Co-ZIF-9 membranes are successfully achieved on the ZnO nanorod-modified porous ceramic tubes. This highly active heteroepitaxial growth may be attributed to the fact that the (Zn,Co) hydroxy double salt intermediate produced in situ from ZnO nanorods acts as heteroseeds and enables the uniform growth of Co-based membranes. The H2/CO2 selectivity of the as-prepared Co-ZIF-9 tubular membrane could reach about 23.8 and the H2/CH4 selectivity of Co-ZIF-67 tubular membrane is as high as 45.4. Moreover, the membranes demonstrate excellent stability because of the ZnO nanorods as linkers between the membrane and substrate.

Hierarchically structured metal–organic frameworks assembled by hydroxy double salt–template synergy with high space–time yields

A simple, green, and versatile method to rapidly synthesize hierarchically structured metal–organic frameworks at room temperature using a cooperative template strategy.