Engineered Amine-Functionalized Metal-Organic Framework to Fabricate a Composite for Next-Generation Asymmetric Supercapacitors with Ultrahigh Performance: Modulating the Energy Storage Barrier.

The present work summarizes the fabrication of an amine-functionalized cadmium-based metal-organic framework (MOF), {[Cd(AT)(BP)]·4DMF}n or Cd_AT-BP, by adopting a simple solvothermal approach using 2-aminoterephthalic acid (AT) as the main linker, while 4,4'-bipyridyl (BP) as an auxiliary linker. The structure of Cd_AT-BP was validated by the single-crystal X-ray diffraction technique that revealed the formation of an overall three-dimensional network with BP acting as a bridge between the 2D sheets of the MOF. The robust framework of Cd_AT-BP decorated with a free amine functional group was utilized for energy storage application. The electrochemical measurements of Cd_AT-BP revealed a maximum areal capacitance of 9.8 mF/cm2 at a scan rate of 5 mV/s. Further, to enhance the practical utility of Cd_AT-BP in energy storage devices, two composites of Cd_AT-BP with reduced graphene oxide (rGO) and multiwalled carbon nanotubes (CNTs), viz., Cd_AT-BP/rGO and Cd_AT-BP/CNT, were prepared by adopting a facile ultrasonication approach. The synthesized Cd_AT-BP/rGO and Cd_AT-BP/CNT composites displayed an impressive areal capacitance of 117 and 37 mF/cm2 (58.5 and 17.5 F/g) at a scan rate of 5 mV/s, respectively, and a capacitance retention of up to 118 and 100% after 5000 cycles at a constant current density of 5 mA/cm2. The highest energy density of about 4.23 mW h/cm2 (2.12 W h/kg) at a current density of 1 mA/cm2 was shown by Cd_AT-BP/rGO among all the three materials attributable to the layered structure of rGO, providing a larger surface area accessible for ion adsorption. Enticed by the remarkable outcomes exhibited by Cd_AT-BP/rGO, we fabricated a two-electrode asymmetric supercapacitor (ASC) device. The developed ASC device revealed energy and power densities of 26.7 mW h/cm2 (13.4 W h/kg) and 3760 mW/cm2 (1880 W/kg), respectively, with a galvanostatic charge-discharge stability of up to 10,000 cycles. The findings identify Cd_AT-BP/rGO as a potential contender for future-generation supercapacitors.

Green Synthesis of ZnO Nanoparticles and Ag-Doped ZnO Nanocomposite Utilizing Sansevieria trifasciata for High-Performance Asymmetric Supercapacitors.

This study provides a comprehensive analysis of a biofabricated nanomaterial derived from Sansevieria trifasciata root extract, evaluating its structural, morphological, and optical properties for use in asymmetric supercapacitors. The nanomaterial comprises pristine ZnO nanoparticles (ZnO NPs) and a 1% Ag-doped ZnO nanocomposite (Ag@ZnO NC), synthesized through a green-assisted sol-gel autocombustion method. Employing techniques such as X-ray diffraction, ultraviolet-visible near-infrared, scanning electron microscopy-energy-dispersive X-rayspectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy, the study confirms a hexagonal wurtzite structure and nanocrystallites with spherical and hexagonal shapes (30 nm). Optical analysis reveals a red shift in the band gap with Ag doping, indicating improved conductivity. The material shows potential applications in solar cells, optoelectronics, spintronics, wastewater treatment, and high-performance asymmetric supercapacitors. Raman spectra validate the wurtzite phase and identify intrinsic defects. Electrochemical tests demonstrate remarkable supercapacitive behavior with a 94% capacitance retention after 10,000 cycles, highlighting its promise as advanced asymmetric supercapacitors.

Eco-friendly synthesis of an α-Fe2O3/rGO nanocomposite and its application in high-performance asymmetric supercapacitors.

This work presents an innovative and environmentally friendly biological synthesis approach for producing α-Fe2O3 nanoparticles (NPs) and the successful synthesis of α-Fe2O3/reduced graphene oxide (rGO) nanocomposites (NCs). This novel synthesis route utilizes freshly extracted albumin, serving as both a reducing agent and a stabilizing agent, rendering it eco-friendly, cost-effective, and sustainable. A combination of characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM) was employed to predict and confirm the formation of the as-synthesized α-Fe2O3 NPs and α-Fe2O3/rGO NCs. Transmission electron microscopy (TEM) verified the anisotropic nature of the synthesized nanoparticles. To gain insight into the enhanced capacitance of the α-Fe2O3/rGO NCs, a series of electrochemical tests, namely cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and stability assessments, were conducted in a conventional three-electrode configuration. Furthermore, a two-electrode asymmetric supercapacitor (ASC) device was fabricated to assess the practical viability of this material. The α-Fe2O3/rGO NCs exhibited a remarkable potential window of 2 V in an aqueous electrolyte, coupled with exceptional cycling stability. Even after undergoing 10 000 cycles, the capacitive retention exceeded 100%, underlining the promising potential of this material for advanced energy storage applications.

Facile synthesis of a three-dimensional Ln-MOF@FCNT composite for the fabrication of a symmetric supercapacitor device with ultra-high energy density: overcoming the energy storage barrier.

In order to quench the thirst for efficient energy storage devices, a novel praseodymium-based state-of-the-art three-dimensional metal-organic framework (MOF), {[Pr(pdc)2]Me2NH2}n (YK-1), has been synthesized by using a simple solvothermal method employing a readily available ligand. YK-1 was characterised by single-crystal XRD and crystallographic analysis. The electrochemical measurements of YK-1 show that it exhibits a specific capacitance of 363.5 F g-1 at a current density of 1.5 A g-1 with 83.8% retention after 5000 cycles. In order to enhance its electrochemical performance for practical application, two composites of YK-1 with graphene oxide (GO) and functionalised multi-walled carbon nanotubes (FCNTs), namely YK-1@GO and YK-1@FCNT, were fabricated by employing a facile ultrasonication technique. The as-synthesized MOF and the composites were characterized by PXRD, FTIR, SEM, and TEM techniques. YK-1@GO and YK-1@FCNT offer enhanced specific capacitances of 488.2 F g-1 and 730.2 F g-1 at the same current density with 93.8% and 97.7% capacity retention after 5000 cycles, respectively (at 16 A g-1). Fascinated by the outstanding results shown by YK-1@FCNT, a symmetric supercapacitor device (SSC) based on it was fabricated. The assembled SSC achieved a remarkable energy density (87.6 W h kg-1) and power density (750.2 W kg-1) at a current density of 1 A g-1, along with very good cycling stability of 91.4% even after 5000 GCD cycles. The SSC device was able to power up several LED lights and even operated a DC brushless fan for a significant amount of time. To the best of our knowledge, the assembled SSC device exhibits the highest energy density among the MOF composite-based SSCs reported so far.

Fabrication of Unique Mixed-Valent CoICoII and CuICuII Metal-Organic Frameworks (MOFs) for Desulfurization of Fuels: A Combined Experimental and Theoretical Approach toward Green Fuel.

Herein, metal-organic framework (MOF)-based adsorbents are designed with distinct hard and soft metal building units, namely, [Co2ICoII(PD)2(BP)] (Co_PD-BP) and [Cu2ICuII(PD)2(BP)] (Cu_PD-BP), where H2PD = pyrazine-1,4-diide-2,3-dicarboxylic acid and BP = 4,4'-bipyridine. The designed MOFs were characterized via spectral and SCXRD techniques, which confirm the mixed-valent states (+1 and +2) of the metal ions. Topological analysis revealed the rare ths and gwg topologies for Co MOF, while Cu-MOF exhibits a unique 8T21 topology in the 8-c net (point symbol for net: {424·64}). Moreover, severe environmental issues can be resolved by effectively removing heterocyclic organosulfur compounds from fuels via adsorptive desulfurization. Further, the developed MOFs were investigated for sulfur removal via adsorptive desulfurization from a model fuel consisting of dibenzothiophene (DBT), benzothiophene (BT), and thiophene (T) in the liquid phase using n-octane as a solvent. The findings revealed that Cu_PD-BP effectively removes the DBT with a removal efficiency of 86% at 300 ppm and an operating temperature of 25 °C, with a recyclability of up to four cycles. The adsorption kinetic analysis showed that the pseudo-first-order model could fit better with the experimental data indicating the physisorption process. Further, the studies revealed that adsorption capacity increased with the increasing initial DBT concentration with a remarkable capacity of 70.5 mg/g, and the adsorption process was well described by the Langmuir isotherm. The plausible reason behind the enhanced removal efficiency shown by Cu_PD-BP as compared to Co_PD-BP could be the soft-soft interactions between soft sulfur and soft Cu metal centers. Interestingly, density functional theory (DFT) studies were done in order to predict the mechanism of binding of thiophenic compounds with Cu_PD-BP, which further ascertained that along with other interactions, the S···π and S···Cu interactions predominate, resulting in a high uptake of DBT as compared to others. In essence, Cu_PD-BP turns out to be a promising adsorbent in the field of fuel desulfurization for the benefit of mankind.

Cu(II) MOFs Based on Bipyridyls: Topology, Magnetism, and Exploring Sensing Ability toward Multiple Nitroaromatic Explosives.

In this work, a series of three copper(II) metal-organic frameworks (MOFs), [Cu(4,4'-DP)Cl] n (1), [Cu(4,4'-DP)0.5Cl] n (2), and [Cu(4,4'-TMDP)Cl] n (3) (4,4'-DP = 4,4'-dipyridyl, 4,4'-TMDP = 4,4'-trimethylenedipyridyl), is designed and synthesized under solvothermal conditions. Crystallographic investigations reveal that 1 and 2 have tetrahedral and 3 has octahedral environment around the Cu(II) ion. By varying the solvent conditions and ligand derivatives, the topology can be interestingly tuned. TOPOS Pro provides topological conclusions that 1 is stabilized by unusual 2D + 2D → 3D polycatenation of layers lying in (110) and (11̅0) planes with dihedral angle of 90° showing altogether fes , hcb , and sql topologies. On the other hand, 2 exhibits a bey (3,4-c net) topology and 3 shows 4-fold interpenetration with the dia topology. The dc measurements for 1-3 performed on polycrystalline samples in a 0.1 T field confirm strong ferromagnetic behaviors for 1 and 2 and moderate antiferromagnetic behavior for 3. To examine the sensing properties of the three MOFs, various hazardous nitroaromatic compounds (NACs) were used as analytes. While 1 is a potent fluorescence sensor for highly sensitive detection of multiple NACs, 2 selectively detects meta-dinitrobenzene (m-DNB) with K SV = 5.73 × 105 M-1 and a remarkably lower limit of detection (LOD) value of 1.23 × 10-7 M. 3 does not show sensing ability toward any NAC probably due to the coordination environment being different from those in 1 and 2. The work demonstrates fine-tuning of the topology and in turn magnetic and sensing properties by changing the reaction conditions.

Aminoalcohols and benzoates-friends or foes? Tuning nuclearity of Cu(ii) complexes, studies of their structures, magnetism, and catecholase-like activities as well as performing DFT and TDDFT studies.

Herein, the coordination chemistry of a series of Cu(ii) complexes of various aminoalcohol and benzoate ligands was explored. The pH-dependent reactions of copper(ii) salts with propanolamine (Hpa), N-methyl diethanolamine (H2mdea), triethanolamine (H3tea), and nbutyl-diethanolamine (H2budea) were carried out in the presence of various benzoates (benzoic acid, 2-hydroxy benzoic acid, 4-hydroxy benzoic acid, 3-methoxy benzoic acid, and 4-methoxy benzoic acid). The resulting complexes [Cu2(pa)2(benzoate)2] (1), [Cu2(pa)2(3-methoxybenzoate)2] (2), [Cu2(pa)2(4-methoxybenzoate)2] (3), [Cu2(H2tea)2(benzoate)2]·2H2O (4), [Cu2(H2tea)2(2-hydroxybenzoate)2]·2H2O (5), [Cu2(H3tea)2(4-hydroxybenzoate)2][Cu(Htea)2]·2H2O (6), [Cu(H2mdea)2][benzoate]2 (7), [Cu(H2mdea)2][4-methoxybenzoate]2 (8), [Cu(H2bdea)2][2-hydroxybenzoate]2 (9), [Cu2(benzoate)4(benzoic acid)2] (10), [Cu2(4-methoxybenzoate)4(CH3CN)2]·4CH3CN (11) and [Cu3(H2tea)2(benzoate)2(NO3)2] (12) were formed as mono-, di- or trinuclear entities depending upon the pH conditions of the reaction. The complexes were characterized employing spectral, magnetic, single-crystal X-ray and DFT/TDDFT studies. 7 and 8 exhibited emission peaks at 510 and 460 nm, respectively, in the solid-state photoluminescence (PL) spectra. The temperature variable magnetic properties of 1-12 revealed the presence of antiferromagnetic (in 1-3 and 7-11) or ferromagnetic interactions (in 4-6 and 12) with Curie constants C = 0.24 (7), 0.28 (8) or 0.35 cm3 K mol-1 (9) and Weiss constants θ = -0.34 (7), -0.32 (8) or -0.40 (9) K for the mononuclear complexes. The dinuclear complexes demonstrated J values of -89.2(2) (1), -71.1(3) (2), -59.6(1) (3), 98(1) (4), 79.1(2) (5), -85.4(2) (10) and -89.5(2) (11) cm-1. Strong ferromagnetic interactions were observed in the case of 6 (J = 172(3) cm-1 and zJ' = 2.3(2) cm-1), which were comparable with those of 12 (J12 = 197(2) cm-1, J13 = -9.3(3) cm-1). A correlation exists between the Cu-O-Cu angle and magnetic coupling in di- and trinuclear Cu(ii) complexes. Moreover, 4-6 were active catalysts for the oxidation of 3,5-DTBC to 3,5-DTBQ and showed catecholase activity in the order 4 > 5 > 6 (Kcat = 943 (4), 698 (5) and 553 h-1 (6)). This order can be rationalized in terms of the electron density on the ligand, which neutralizes the effective positive charge on Cu(ii), thus forming the less or more stable intermediate. The order of catecholase activity and the electronic spectral properties of 4-6 were also investigated by DFT and TDDFT studies, respectively.