Synthesis and Characterization of Cu-MOF Derived Cu@AC Electrocatalyst for Oxygen Reduction Reaction in PEMFC

Nanoporous air filtering systems made from renewable sources: benefits and challenges

There is a crucial need for air purification systems due to increasing air contamination, while conventional air-filtering materials face challenges in eliminating gaseous and particulate pollutants. This review examines the development and characteristics of nanoporous polymeric materials developed from renewable resources, which have rapidly advanced in recent years. These materials offer more sustainable alternatives for nanoporous structures made out of conventional polymers and significantly impact the properties of porous polymers. The review explores nanoporous materials' production from renewable sources, filtering mechanisms, physicochemical makeup, and sensing capabilities. The recent advancements in this field aim to enhance production techniques, lower pressure drop, and improve adsorption efficiency. Currently, supporting approaches include using adsorbent layers and binders to immobilize nanoporous materials. Furthermore, the prospects and challenges of nanoporous materials obtained from renewable sources used for air purification are discussed.

Terrace-Like 2D Hierarchically Porous Iron/Cobalt Metal-Organic Framework: Ambient Fast Synthesis and Efficient Oxygen Evolution Reaction Application

It is urgent to design a low-cost electrocatalyst with high activity to enhance the efficiency of oxygen evolution reaction (OER), which is limited by the slow four-electron transfer kinetics process. Nevertheless, traditional synthetic methods, including calcination and solvothermal, of the electrocatalysts are high-cost, low-yield, and energy-hogging, which limits their industrial application. Herein, an ambient fast synthetic method is developed to prepare terrace-like Fe/Co bimetal-organic framework (TFC-MOF) electrocatalyst materials in gram scale in 1 h. The method in this paper is designable based on coordination chemistry. Fe and Co ions can coordinate with the carboxyl groups on benzene-1,3,5-tricarboxylic acid (H3 BTC) to form a 2D-MOF structure. Structural characterizations, including SEM, TEM, and XRD are conducted to verify that the TFC-MOF is a terrace-like layered structure with uniform-sized mesoporous, which reduces the adsorption steric hindrance and facilitates the mass and electron transfer efficiency of OER. The TFC-MOF shows low overpotential, 255 mV at a current density of 10 mA cm-2 , and a low Tafel slope of 49.9 mV dec-1 , in an alkaline solution. This work provides a planar coordination strategy to synthesize 2D-MOF OER electrocatalyst on a large scale with low cost and low energy consumption, which will promote its practical OER applications.

Investigation of the effect of Ni and Cu variant MOF-74 in the Polydimethylsiloxane (PDMS)-based Mixed Matrix Membranes (MMMs) for efficient gas separation applications

Mixed matrix membranes (MMMs) containing metal-organic frameworks (MOFs) have been an emerging and promising membrane technology to contribute to different gas separation applications including carbon dioxide (CO2) and oxygen (O2) separation, because of their large surface areas and distinctive gas adsorption features. In this work, the fabrication process of Polydimethylsiloxane (PDMS)-based MMMs was reported, in which 0.5 to 2 wt.% of each type of (Cu, Ni)-based MOF-74 variants were incorporated into a PDMS matrix in order to achieve high CO2/N2, O2/N2, and CO2/O2 separation efficiency. These MMMs and their nanofillers (MOF-74) were extensively characterized using scanning electron microscopy (SEM) along with Energy Dispersive X-Ray (EDX) mapping, X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), a single gas permeation testing system, and an ultimate tensile strength testing (UTS) unit in order to gain insight into their properties in relation to their gas separation performance. The 1 wt.% of both (Cu and Ni)-MOF-74@PDMS were selected as the most optimum MMMs due to their uniform morphology and enhanced tensile strength, which exhibited high CO2 permeabilities of 4432 Barrer (37.9% increase) and 4288 Barrer (33.5% increase), respectively. Furthermore, in the case of 1 wt.% Ni-MOF-74@PDMS, the CO2/N2, O2/N2, and CO2/O2 selectivities were also enhanced to 36.2 (141.6% increase), 3.2 (21.9% increase), and 11.25 (98.1% increase), respectively. While, in the case of 1 wt.% Cu-MOF-74@PDMS the CO2/N2 and O2/N2 selectivities showed an increment up-to 94.7 (531.5% increase) and 6.47 (145% increase), respectively, Whereas, at 0.5 wt.%, Cu-MOF-74@PDMS showed the best CO2/O2 selectivity of 25.26 (344.7% increase).

A zeolitic imidazolate framework (ZIF-67) and graphitic carbon nitride (g-C3N4) composite based efficient electrocatalyst for overall water-splitting reaction

Designing of non-noble, cost-effective, sustainable catalysts for water splitting is essential for hydrogen production. In this research work, ZIF-67, g-C3N4, and their composite (1, 3, 5, 6, 8 wt% g-C3N4@ZIF-67) are synthesized, and various techniques, XRD, FTIR, SEM, EDX and BET are used to examine their morphological properties for electrochemical water-splitting. The linkage of ZIF-67 with g-C3N4 synergistically improves the electrochemical kinetics. An appropriate integration of g-C3N4 in ZIF-67 MOF improves the charge transfer between the electrode and electrolyte and makes it a suitable option for electrochemical applications. In alkaline media, the composite of ZIF-67 MOF with g-C3N4 over a Ni-foam exhibits a superior catalyst activity for water splitting application. Significantly, the 3 wt% g-C3N4@ZIF67 composite material reveals remarkable results with low overpotential values of -176 mV@10 mA cm-2, 152 mV@10 mA cm-2 for HER and OER. The catalyst remained stable for 24 h without distortion. The 3 wt% composite also shows a commendable performance for overall water-splitting with a voltage yield of 1.34 v@10 mA cm-2. The low contact angle (54.4°) proves the electrocatalyst's hydrophilic nature. The results of electrochemical water splitting illustrated that 3 wt% g-C3N4@ZIF-67 is an electrically conductive, stable, and hydrophilic-nature catalyst and is suggested to be a promising candidate for electrochemical water-splitting application.

Ferrocene anchored activated carbon as a versatile catalyst for the synthesis of 1,5-benzodiazepines via one-pot environmentally benign conditions

1,5-Benzodiazepine is considered as one of the central moieties in the core unit of most drug molecules. Construction of such moieties with a new C–N bond under solvent-free and mild reaction conditions is challenging. Herein, we present a benign protocol for one pot synthesis of 1,5-benzodiazepine derivatives by using ferrocene (FC) supported activated carbon (AC) as a heterogeneous catalyst. The catalyst FC/AC was characterized by several analytical and spectroscopic techniques to reveal its physicochemical properties and for structural confirmation. The synthesized catalyst FC/AC was explored for its catalytic activity in the synthesis of 1,5-benzodiazepines through condensation of o-phenylenediamine (OPDA) and ketones (aromatic and aliphatic) under solvent-free conditions. The robust 10 wt% FC/AC catalyst demonstrated appreciable activity with 99% conversion of diamines and 91% selectivity towards the synthesis of the desired benzodiazepine derivatives under solvent-free conditions at 90 °C in 8 h. Additionally, several reaction parameters such as catalyst loading, reaction temperature, effect of reaction time and effect of different solvents on selectivity were also studied and discussed in-depth. To understand the scope of the reaction, several symmetrical and unsymmetrical ketones along with different substituted diamines were tested with the synthesized catalyst. All prepared reaction products were obtained in good to efficient yields and were isolated and identified as 1,5-benzodiazepines and no side products were observed. The obtained catalyst characterization data and the activity studies suggested that, the synergetic effect occurred due to the uniform dispersion of ferrocene over the AC surface with numerous acidic sites which triggered the reaction of diamine and ketone to form the corresponding benzodiazepine derivative and the same was illustrated in the plausible mechanism. Furthermore, the synthesized catalyst was tested for leaching and recyclability, and the results confirmed that catalyst can be used for up to six consecutive cycles without much loss in the catalytic activity and its morphology which makes the process sustainable and economical for scale-up production. The present method offered several advantages such as an ecofriendly method, excellent yields, sustainable catalytic transformation, easy work-up and isolation of products, and quick recovery of catalyst.

1,5-Benzodiazepine is considered as one of the central moieties in the core unit of most drug molecules.

Recent Advancements in the Fabrication of Functional Nanoporous Materials and Their Biomedical Applications

Functional nanoporous materials are categorized as an important class of nanostructured materials because of their tunable porosity and pore geometry (size, shape, and distribution) and their unique chemical and physical properties as compared with other nanostructures and bulk counterparts. Progress in developing a broad spectrum of nanoporous materials has accelerated their use for extensive applications in catalysis, sensing, separation, and environmental, energy, and biomedical areas. The purpose of this review is to provide recent advances in synthesis strategies for designing ordered or hierarchical nanoporous materials of tunable porosity and complex architectures. Furthermore, we briefly highlight working principles, potential pitfalls, experimental challenges, and limitations associated with nanoporous material fabrication strategies. Finally, we give a forward look at how digitally controlled additive manufacturing may overcome existing obstacles to guide the design and development of next-generation nanoporous materials with predefined properties for industrial manufacturing and applications.

Understanding the endocrine disruptor and determination of bisphenol A by functional Cu-BTABB-MOF/rGO composite as facile rapid electrochemical sensor: an experimental and DFT investigation

A pioneering CuBTABB-MOF/rGO composite customized electrode is fabricated and utilized as a sensor towards identifying bisphenol A (BPA) in a phosphate buffer solution of pH 7.0. The composite is characterized by FTIR, Raman spectroscopy, XRD, SEM, EDX, HRTEM, and XPS to study its structural and morphological properties. Compared with Cu-BTABB-MOF and Cu-BTABB-MOF@GO, the Cu-BTABB-MOF@rGO modified electrode is more sensitive and selective to BPA due to a strong interaction between them. The developed Cu-BTABB-MOF@rGO modified electrode exhibits good sensitivity (6.95 × 10^-5 A mol^-1 L^-1) for BPA having a wide linear range of 0-100 μmol L^-1 with the LOD of 2.08 × 10^-5 mol L^-1, reproducibility of 4.35%, and relative standard deviation (RSD) and stability of 90% for thirty days. In addition, the developed electrocatalyst remained unoccupied from interfering substances and consequently provided an encouraging platform for swift detection of BPA in real samples such as pond water and packed water bottles. Additionally, we utilized DFT (density functional theory) to model GO and Cu-BTABB-MOF structures for detecting BPA molecules.

A label-free electrochemical platform based on a thionine functionalized magnetic Fe-N-C electrocatalyst for the detection of microRNA-21

Taking a composite of a nanomaterial and a signal molecule as a substrate material can provide a label-free electrochemical platform. Besides, the nanomaterial with a high catalytic activity towards the signal molecule can improve the sensitivity of the platform. Herein, a thionine functionalized Fe-N-C nanocomposite was employed as the substrate. Firstly, the electrocatalytic activity of Fe-N-C towards the electroreduction of thionine was explored. Then, an immobilization-free and label-free electrochemical platform for the determination of microRNA-21 based on Fe-N-C-thionine/Fe₃O₄@AuNPs was constructed. A magnetic glassy carbon electrode (MGCE) was used to keep the magnetic Fe-N-C-thionine/Fe₃O₄@AuNPs modified onto the surface of the MGCE. Fe-N-C and Fe₃O₄ nanoparticles can co-catalyze the electroreduction of thionine and a strong electrochemical reduction signal of thionine could be realized in the differential pulse voltammetry (DPV) test. Also, a catalytic hairpin assembly (CHA) reaction was utilized to enhance the sensitivity of the developed electrochemical biosensor. Besides, the developed biosensor shows excellent specificity and reproducibility in the test of human serum samples, indicating its wide application prospects in the early-stage diagnosis of tumors.

ZIF-67 Derived MnO2 Doped Electrocatalyst for Oxygen Reduction Reaction

In this study, zeolitic imidazolate framework (ZIF-67) derived nano-porous carbon structures that were further hybridized with MnO2 were tested for oxygen reduction reaction (ORR) as cathode material for fuel cells. The prepared electrocatalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive X-ray Analysis (EDX). Cyclic voltammetry was performed on these materials at different scan rates under dissolved oxygen in basic media (0.1 M KOH), inert and oxygen rich conditions to obtain their I–V curves. Electrochemical impedance spectroscopy (EIS) and Chronoamperometry was also performed to observe the materials’ impedance and stability. We report improved performance of hybridized catalyst for ORR based on cyclic voltammetry and EIS results, which show that it can be a potential candidate for fuel cell applications.

Zeolitic imidazolate framework (ZIF)-derived porous carbon materials for supercapacitors: an overview

The present analysis focuses on the synthetic methods used for the application of supercapacitors with various mysterious architectures derived from zeolitic imidazolate frameworks (ZIFs). ZIFs represent an emerging and unique class of metal–organic frameworks with structures similar to conventional aluminosilicate zeolites, consisting of imidazolate linkers and metal ions. Their intrinsic porous properties, robust functionalities, and excellent thermal and chemical stabilities have resulted in a wide range of potential applications for various ZIF materials. In this rapidly expanding area, energetic research activities have emerged in the past few years, ranging from synthesis approaches to attractive applications of ZIFs. In this analysis, the development of high-performance supercapacitor electrodes and recent strategies to produce them, including the synthesis of various heterostructures and nanostructures, are analyzed and summarized. This analysis goes via the ingenuity of modern science when it comes to these nanoarchitecture electrodes. Despite these significant achievements, it is still difficult to accurately monitor the morphologies of materials derived from metal–organic frameworks (MOFs) because the induction force during structural transformations at elevated temperatures is in high demand. It is also desirable to achieve the direct synthesis of highly functionalized nanosized materials derived from zeolitic imidazolate frameworks (ZIFs) and the growth of nanoporous structures based on ZIFs encoded in specific substrates for the construction of active materials with a high surface area suitable for electrochemical applications. The latest improvements in this field of supercapacitors with materials formed from ZIFs as electrodes using ZIFs as templates or precursors are discussed in this review. Also, the possibility of usable materials derived from ZIFs for both existing and emerging energy storage technologies is discussed.

The present analysis focuses on the synthetic methods used for the application of supercapacitors with various mysterious architectures derived from zeolitic imidazolate frameworks (ZIFs).

Synthesis and Performance of MOF-Based Non-Noble Metal Catalysts for the Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells: A Review

Hydrogen is widely regarded as a prime energy carrier for bridging the gap between renewable energy supply and demand. As the energy-generating component of the hydrogen cycle, affordable and reliable fuel cells are of key importance to the growth of the hydrogen economy. However, the use of scarce and costly Pt as an electrocatalyst for the oxygen reduction reaction (ORR) remains an issue to be addressed, and in this regard, metal-organic frameworks (MOFs) are viewed as promising non-noble alternatives because of their self-assembly capability and tunable properties. Herein, recent (2018-2020) works on MOF-based electrocatalysts containing N-doped C, Mn, Fe, Co, multiple metals, and multiple sites are reviewed and summarized with a focus on ORR activity, and the principal physicochemical properties and electrochemical performance of these catalysts realized using rotating electrodes are compared.

Investigation on Electroreduction of CO2 to Formic Acid Using Cu3(BTC)2 Metal-Organic Framework (Cu-MOF) and Graphene Oxide

A recent class of porous materials, viz., metal-organic frameworks (MOFs), finds applications in several areas. In this work, Cu-based MOFs (Cu-benzene-1,3,5-tricarboxylic acid) along with graphene oxide, viz., Cu-MOF/GO, are synthesized and used further for reducing CO2 electrochemically. The reduction was accomplished in various supporting electrolytes, viz., KHCO3/H2O, tetrabutylammonium bromide (TBAB)/dimethylformamide (DMF), KBr/CH3OH, CH3COOK/CH3OH, TBAB/CH3OH, and tetrabutylammonium perchlorate (TBAP)/CH3OH to know their effect on product formation. The electrode fabricated with the synthesized material was used for testing the electroreduction of CO2 at various polarization potentials. The electrochemical reduction of CO2 is carried out via the polarization technique within the experimented potential regime vs saturated calomel electrode (SCE). Ion chromatography was employed for the analysis of the produced products in the electrolyte, and the results showed that HCOOH was the main product formed through reduction. The highest concentrations of HCOOH formed for different electrolytes are 0.1404 mM (-0.1 V), 66.57 mM (-0.6 V), 0.2690 mM (-0.5 V), 0.2390 mM (-0.5 V), 0.7784 mM (-0.4 V), and 0.3050 mM (-0.45 V) in various supporting electrolyte systems, viz., KHCO3/H2O, TBAB/DMF, KBr/CH3OH, CH3COOK/CH3OH, TBAB/CH3OH, and TBAP/CH3OH, respectively. The developed catalyst accomplished a significant efficiency in the conversion and reduction of CO2. A high faradic efficiency of 58% was obtained with 0.1 M TBAB/DMF electrolyte, whereas for Cu-MOF alone, the efficiency was 38%. Thus, the work is carried out using a cost-effective catalyst for the conversion of CO2 to formic acid than using the commercial electrodes. The synergistic effect of GO sheets at 3 wt % concentration and Cu+OH- interaction leads to the formation of formic acid in various electrolytes.

MOF-Derived CuPt/NC Electrocatalyst for Oxygen Reduction Reaction

Metal-organic frameworks (MOFs) have been at the center stage of material science in the recent past because of their structural properties and wide applications in catalysis. MOFs have also been used as hard templates for the preparation of catalysts. In this study, highly active CuPt/NC electrocatalyst was synthesized by pyrolyzing Cu-tpa MOF along with Pt precursor under flowing Ar-H2 atmosphere. The catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). Rotating disk electrode study was performed to determine the oxygen reduction reaction (ORR) activity for CuPt/NC in 0.1 M HClO4 at different revolutions per minute (400, 800, 1200, and 1600) and it was also compared with commercial Pt/C catalyst. Further the ORR performance was evaluated by K-L plots and Tafel slope. CuPt/NC shows excellent ORR performance with onset potential of 0.9 V (vs. RHE), which is comparable with commercial Pt/C. The ORR activity of CuPt/NC is demonstrated as an efficient electrocatalyst for fuel cell.

Practical MOF Nanoarchitectonics: New Strategies for Enhancing the Processability of MOFs for Practical Applications

Over the past decades, the development of porous materials has directly or indirectly affected industrial production methods. Metal-organic frameworks (MOFs) as an emerging class of porous materials exhibit some unique advantages, including controllable composition, a large surface area, high porosity, and so on. These attractive characteristics of MOFs have led to their potential applications in energy storage and conversion devices, drug delivery, adsorption and storage, sensors, and other areas. However, powdered MOFs have limited practical applications owing to poor processability, safety hazards from dust formation, and poor recyclability. In addition, the inherent micro/mesoporosities of MOFs also reduce the accessibility and diffusion kinetics for large molecules. To improve their processability for practical applications, MOFs are often deposited as MOF layers or films (i.e., MOF-coated composites) on supporting materials or are formed into 3D structured composites, such as aerogels and hydrogels. In this article, we review recent researches on these MOF composites, including their synthetic methods and potential applications in energy storage devices, heavy metal ion adsorption, and water purification. Finally, the future outlook and challenges associated with the large-scale fabrication of MOF-based composites for practical applications are discussed.

Thermally reduced mesoporous manganese MOF @reduced graphene oxide nanocomposite as bifunctional electrocatalyst for oxygen reduction and evolution

Oxygen electrocatalysis plays a crucial role in harnessing energy from modern renewable energy technologies like fuel cells and metal–air batteries. But high cost and stability issues of noble metal catalysts call for research on tailoring novel metal–organic framework (MOF) based architectures which can bifunctionally catalyze O₂ reduction and evolution reactions (ORR & OER). In this work, we report a novel manganese MOF @rGO nanocomposite synthesized using a facile self-templated solvothermal method. The nanocomposite is superior to commercial Pt/C catalyst both in material resource and effectiveness in application. A more positive cathodic peak (E_pc = 0.78 V vs. RHE), onset (E_onset = 1.09 V vs. RHE) and half wave potentials (E_1/2 = 0.98 V vs. RHE) for the ORR and notable potential to achieve the threshold current density (E_{@10 mA cm⁻²}= 1.84 V vs. RHE) for OER are features promising to reduce overpotentials during ORR and OER. Small Tafel slopes, methanol tolerance and acceptable short term stability augment the electrocatalytic properties of the as-prepared nanocomposite. Remarkable electrocatalytic features are attributed to the synergistic effect from the mesoporous 3D framework and transition metal–organic composition. Template directed growth, tunable porosities, novel architecture and excellent electrocatalytic performance of the manganese MOF @rGO nanocomposite make it an excellent candidate for energy applications.

Oxygen electrocatalysis plays a crucial role in harnessing energy from modern renewable energy technologies like fuel cells and metal–air batteries.