Synthesis of Supported Nickel Nanoparticles via a Nonthermal Plasma Approach and Its Application in CO₂ Reforming of Methane

A microwave plasma treatment was applied to obtain not only a desired strong metal–support interaction but also well-dispersed nickel nanoparticles supported on ceria. The catalytic properties of these supported nanoparticles were tested in CO₂ reforming of methane. The plasma-treated Ni/CeO₂ catalysts showed enhanced turnover frequencies (TOFs), normalized by Ni on the surface, as compared with the thermally calcined samples. The Ni/CeO₂ treated under plasma with low Ni loading gave an enhanced TOF of 9.5 s^–1 (700 °C, 50% CH₄ and 50% CO₂, and 1 atm) as compared with the thermally calcined catalyst (8.7 s^–1). Increasing the Ni loading on the plasma-treated Ni/CeO₂ catalysts gave an improved TOF (10.4 s^–1) which was stable with time, while the TOF was observed to drop by a factor of 2 relative to the optimal TOF on the thermally calcined catalyst after 5 h. For the plasma-treated samples, concurrent treatment of both the uncalcined ceria support and the loaded metal precursor generated strong metal–support interaction and formation of well-dispersed Ni particles, resulting in a superior and stable TOF with time. In the case of thermally calcined catalysts, the weak metal–support interaction and the agglomeration of Ni clusters together with the migration of the Ni particles into the ceria support hindered the accessibility of active nickel sites, resulting in deactivation of the materials during reaction. Moreover, high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, H₂ temperature-programmed reduction, and X-ray photoelectron spectroscopy yielded a clear picture of the impact of microwave plasma treatment on the nickel particle size, shape, distribution, and interaction with the ceria support

Nitrogen-Doped Carbon Foams Synthesized from Banana Peel and Zinc Complex Template for Adsorption of CO₂, CH₄, and N₂

We report nitrogen-doped, activated carbon foams prepared from banana peels using a self-template method with zinc nitrate, 2-aminophenol, and furfural involved. Importantly, we have extended the banana peel zinc complex soft-template method to investigate the effects of carbonization temperature and postcarbonization CO₂ activation on the carbon pore structure, and examined the effect of N-content on the carbon foam’s equilibrium adsorption capacity for CO₂. The carbon foams contain up to 6.0 wt % nitrogen and feature cellular macroporous structures with BET specific surface areas up to 1426 m²·g^–1. The potential of the carbon foams for CO₂/N₂, CO₂/CH₄, and CH₄/N₂ separations was evaluated by measurement of pure fluid adsorption capacities using a gravimetric adsorption apparatus and calculation of adsorption selectivies at a range of conditions using ideal adsorption solution theory (IAST). The adsorption capacities at a 4000 kPa and 298 K were CO₂ 9.21 mmol·g^–1, CH₄ 5.29 mmol·g^–1, and N₂ 3.29 mmol·g^–1

Porous Polyethersulfone-Supported Zeolitic Imidazolate Framework Membranes for Hydrogen Separation

ZIF-8 thin layer has been synthesized on the asymmetric porous polyethersulfone (PES) substrate via secondary seeded growth. Continuous and dense ZIF-8 layer, containing microcavities, has good affinity with the PES support. Single gas permeance was measured for H₂, N₂, CH₄, O₂, and Ar at different pressure gradients and temperatures. Molecular sieving separation has been achieved for selectively separating hydrogen from larger gases. At 333 K, the H₂ permeance can reach ∼4 × 10^–7 mol m^–2 s^–1 Pa^–1, and the ideal separation factors of H₂ from Ar, O₂, N₂, and CH₄ are 9.7, 10.8, 9.9, and 10.7, respectively. Long-term hydrogen permeance and H₂/N₂ separation performance show the stable permeability of the derived membranes

Porous Scandia-Stabilized Zirconia Layer for Enhanced Performance of Reversible Solid Oxide Cells

Reversible solid oxide cells (RSOCs) developed so far display short-term stability during solid oxide electrolysis cell (SOEC) mode. This is due to the delamination of the strontium-doped lanthanum manganite (LSM) air electrode when tested for a long time. Here, we report a highly stable RSOC operation of LSM for 5 cycles using half and full cells. A scandia-stabilized zirconia (SSZ) porous layer was applied between the dense SSZ electrolyte and the porous LSM electrode. The half-cells were tested under ±0.5 A cm^–2, whereas the full cells were tested at +0.5 and −0.25 A cm^–2 at 800 °C. It was found that the cells with a porous SSZ layer are stable and show a performance increase after five RSOC cycles. The ohmic and polarization resistance of both the half and full cells decreased after each cycle. Also, the maximum power density of the full cell increased from 425 to 550 mW cm^–2, whereas the electrolysis current density increased from 294 to 407 mA cm^–2 after 5 cycles at 1.3 V in 10% H₂O/90% H₂, at 800 °C. This performance enhancement can be ascribed to the creation of oxygen vacancies in LSM under applied current, the alleviation of oxygen partial pressure from the interface and the introduction of electronic conductivity in the electrolyte near the interface. The cell without the SSZ porous layer experienced the zirconate formation, high oxygen partial pressure at the interface as well as the silver deposition at the electrode–electrolyte interface. Therefore, an increase in the polarization resistance for the half-cell and a decrease in the electrolysis current density for the full cell were observed

Mixed Matrix Membranes with Strengthened MOFs/Polymer Interfacial Interaction and Improved Membrane Performance

MOFs-based mixed matrix membranes (MMMs) have attracted extensive attention in recent years due to their potential high separation performance, the low cost, and good mechanical properties. However, it is still very challenging to achieve defect-free interface between micrometer-sized MOFs and a polymer matrix. In this study, [Cd₂L­(H₂O)]₂·5H₂O (Cd-6F) synthesized using 4,4′-(hexafluoroisopropylidene)­diphthalic anhydride (6FDA) as an organic ligand was introduced into the 6FDA-ODA polyimide matrix to achieve novel MOF MMMs. A specific interfacial interaction between MOF crystals and polymer chains was innovatively targeted and achieved through in situ polymerization procedure. The enhanced adhesion between MOF particles and polymer phase was observed, and the improved interfacial interaction between Cd-6F and the 6FDA-ODA polyimide matrix was confirmed by detailed characterizations including FTIR and NMR. In the meantime, the gas permeance and selectivity of the MMMs are strongly dependent on their morphology. The MMM derived from in situ polymerization presents excellent interfaces between micrometer-sized MOF crystals and the polymer matrix, resulting in increased permeability and selectivity. The strategy shown here can be further utilized to select the MOF/polymer pair, eliminate interfacial voids, and improve membrane separation performance of MOFs-based MMMs

Uncommon Pyrazoyl-Carboxyl Bifunctional Ligand-Based Microporous Lanthanide Systems: Sorption and Luminescent Sensing Properties

Seven new isostructural lanthanide metal–organic frameworks (Ln-MOFs), [Ln­(Hpzbc)₂(NO₃)]·H₂O (<b>1-Ln</b>, Ln = Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Er³⁺, and Yb³⁺ ions, H₂pzbc = 3-(1<i>H</i>-pyrazol-3-yl) benzoic acid), with one-dimensional (1D) channels decorated by nitrate anions and pyrazoyl groups have been constructed. <b>1-Ln</b>, as revealed by structural analysis, represent uncommon microporous 3D Ln-pyrazoyl-carboxyl systems using pyrazoyl-carboxyl bifunctional ligands as bridges. The luminescent investigations show that <b>1-Eu</b> is an excellent MOF-based fluorescent probe, with high sensitivity, selectivity, and simple regeneration, for environmentally relevant Fe³⁺ and Cr₂O₇^2– ions. <b>1-Eu</b> also presents highly selective capture for CO₂ over N₂ and CH₄ due to the multiple binding sites for CO₂ molecules, which were supported by Grand Canonical Monte Carlo (GCMC) simulations

Honeycomb Metal–Organic Framework with Lewis Acidic and Basic Bifunctional Sites: Selective Adsorption and CO₂ Catalytic Fixation

Carrying out the strategy of incorporating rod secondary building units and polar functional groups in metal–organic frameworks (MOFs) to accomplish the separation of CO₂ and C₂ hydrocarbons over CH₄ as well as CO₂ fixation, an oxalamide-functionalized ligand <i>N</i>,<i>N</i>′-bis­(isophthalic acid)-oxalamide (H₄BDPO) has been designed. The solvothermal reaction of H₄BDPO with the oxophilic alkaline-earth Ba²⁺ ion afforded a honeycomb Ba-MOF, {[Ba₂(BDPO)­(H₂O)]·DMA}<i>_n</i> (<b>1</b>). Due to the existence of Lewis basic oxalamide groups and unsaturated Lewis acid metal sites in the tubular channels, the activated framework presents not only high C₂H₆, C₂H₄, and CO₂ uptakes and selective capture from CH₄, but also efficient CO₂ chemical fixation as a recyclable heterogeneous catalyst. Grand canonical Monte Carlo simulations were combined to explore the adsorption selectivities for C₂H₆–CH₄ and C₂H₄–CH₄ mixtures as well as the interaction mechanisms between the framework and epoxides

Honeycomb Metal–Organic Framework with Lewis Acidic and Basic Bifunctional Sites: Selective Adsorption and CO₂ Catalytic Fixation

Carrying out the strategy of incorporating rod secondary building units and polar functional groups in metal–organic frameworks (MOFs) to accomplish the separation of CO₂ and C₂ hydrocarbons over CH₄ as well as CO₂ fixation, an oxalamide-functionalized ligand <i>N</i>,<i>N</i>′-bis­(isophthalic acid)-oxalamide (H₄BDPO) has been designed. The solvothermal reaction of H₄BDPO with the oxophilic alkaline-earth Ba²⁺ ion afforded a honeycomb Ba-MOF, {[Ba₂(BDPO)­(H₂O)]·DMA}<i>_n</i> (<b>1</b>). Due to the existence of Lewis basic oxalamide groups and unsaturated Lewis acid metal sites in the tubular channels, the activated framework presents not only high C₂H₆, C₂H₄, and CO₂ uptakes and selective capture from CH₄, but also efficient CO₂ chemical fixation as a recyclable heterogeneous catalyst. Grand canonical Monte Carlo simulations were combined to explore the adsorption selectivities for C₂H₆–CH₄ and C₂H₄–CH₄ mixtures as well as the interaction mechanisms between the framework and epoxides

Uncommon Pyrazoyl-Carboxyl Bifunctional Ligand-Based Microporous Lanthanide Systems: Sorption and Luminescent Sensing Properties

Seven new isostructural lanthanide metal–organic frameworks (Ln-MOFs), [Ln­(Hpzbc)₂(NO₃)]·H₂O (<b>1-Ln</b>, Ln = Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Er³⁺, and Yb³⁺ ions, H₂pzbc = 3-(1<i>H</i>-pyrazol-3-yl) benzoic acid), with one-dimensional (1D) channels decorated by nitrate anions and pyrazoyl groups have been constructed. <b>1-Ln</b>, as revealed by structural analysis, represent uncommon microporous 3D Ln-pyrazoyl-carboxyl systems using pyrazoyl-carboxyl bifunctional ligands as bridges. The luminescent investigations show that <b>1-Eu</b> is an excellent MOF-based fluorescent probe, with high sensitivity, selectivity, and simple regeneration, for environmentally relevant Fe³⁺ and Cr₂O₇^2– ions. <b>1-Eu</b> also presents highly selective capture for CO₂ over N₂ and CH₄ due to the multiple binding sites for CO₂ molecules, which were supported by Grand Canonical Monte Carlo (GCMC) simulations

Solvent or Temperature Induced Diverse Coordination Polymers of Silver(I) Sulfate and Bipyrazole Systems: Syntheses, Crystal Structures, Luminescence, and Sorption Properties

Three new coordination polymers, [Ag₄(H₂bpz)₄(SO₄)₂]·H₂O (<b>1</b>), [Ag₂(H₂bpz)₂(SO₄)]·3H₂O (<b>2</b>), and [Ag₃(H₂bpz)₄]­(SO₄)_2/3(OH)_5/3·4H₂O (<b>3</b>) have been solvothermally synthesized with Ag₂SO₄ and flexible ligand 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (H₂bpz) in different solvents and temperatures. Complex <b>1</b> is a 2-fold interpenetrated three-dimensional (3D) framework with an uncommon (3,5)-connected hms topology. Complex <b>2</b> is a structural isomer of <b>1</b> and shows a three-connected 2D ths net consisting of interesting 3-fold and 2-fold heterochiral helical chains. Complex <b>3</b> discloses a grid layer structure, containing heterochiral helical chains and an unusual <i>meso-</i>helix. More interestingly, three sets of layers in <b>3</b> stack in different directions, affording an unprecedented 2D + 2D + 2D → 3D polycatenating cationic framework with 1D + 3D porous systems. In <b>1</b>–<b>3</b>, H₂bpz exhibit exobidentate bridging fashions with wide-ranged interpyrazole tilting angles and changeable coordination configurations, such as <i>cis</i> and <i>trans</i> fashions in <b>1</b> and <b>3</b> and uniform <i>trans</i> fashion in <b>2</b>. These lead to the isomeric [Ag­(H₂bpz)]_<i>n</i> arrays of wavelike and helical chains in <b>1</b> and <b>2</b>, respectively. Complexes <b>1</b>–<b>3</b> display solid-state photoluminescence stemming from the ligand-centered fluorescent emissions of H₂bpz. Because of the highly polar framework, <b>3</b> shows excellent adsorption selectivity for CO₂ over N₂