Porous Catalyst Research Articles

Cobalt-Cluster-Based Metal-Organic-Framework-Catalyzed Carboxylative Cyclization of Propargylic Amines with CO2 from Flue Gas.

The fixation of carbon dioxide (CO2) directly from flue gas into valuable chemicals like 2-oxazolidinones is of great significance for economic and environmental benefits, which is typically catalyzed by noble-metal catalysts and under harsh conditions. Herein, a novel 2-fold interpenetrated framework {[Co3(μ2-O)(TCA)2(HDPTA)2]·2H2O·2DMF}n [Co(II)-based metal-organic framework (Co-MOF)] containing [Co3] clusters and highly dense amino groups (-NH2) dispersed in the channel was prepared, exhibiting high solvent/pH stability and CO2 adsorption capacity (24.9 cm3·g-1). Catalytic experiments demonstrated that Co-MOF could catalyze the carboxylative cyclization of propargylic amines to generate 2-oxazolidinones with yields of up to 98% under mild conditions with CO2 directly from flue gas. In addition, Co-MOF retained its structure and catalytic activity after five-cycle catalytic experiments, showing the promising practical application. Density functional theory (DFT) calculation suggested that the [Co3] centers in the MOF activated the C≡C of propargylic amines with much more binding energy than Co(NO3)2, partly accounting for the high catalytic activity of Co-MOF. This work demonstrates the first Co-based MOF material that is highly efficient for carboxylative cyclization of propargylic amines with flue gas as the CO2 source, inspiring further rational design of porous catalysts for efficient CO2 utilization.

Robust Spray Combustion Enabling Hierarchical Porous Carbon-Supported FeCoNi Alloy Catalyst for Zn-Air Batteries.

Rechargeable Zn-air batteries (RZABs) are poised for industrial application, yet they require low-cost, high-performance catalysts that efficiently facilitate both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The pivotal challenge lies in designing multimetal active sites and optimizing the carbon skeleton structure to modulate catalyst activity. In this study, we introduce a novel hierarchical porous carbon-supported FeCoNi bifunctional catalyst, synthesized via a spray combustion method. The carbon, derived from sucrose, was tailored into a hierarchical porous morphology through etching with NO3- ions and NaCl, thereby significantly increasing the surface area for the interaction of the O2 and electrolyte interaction. The in situ formation of FeCoNi alloy nanoparticles ensures their uniform dispersion and anchoring, facilitating electron transport. The strong interaction and charge transfer at the heterogeneous FeCoNi alloy interfaces, along with nitrogen doping, which enhances the OER/ORR activity, endow the FeCoNi/N-PC catalyst with exceptional bifunctional catalytic properties, characterized by an activity parameter of 0.73 V. Furthermore, the RZAB assembled with this catalyst demonstrates outstanding cycling stability and reversibility, with a minimal round-trip efficiency decay of 7.6% over 1380 cycles (460 h) at 10 mA cm-2.

Enhancing CO oxidation performance by controlling the interconnected pore structure in porous three-way catalyst particles.

Highly ordered porous structured particles comprising three-way catalyst (TWC) nanoparticles have attracted attention because of their remarkable catalytic performance. However, the conditions for controlling their pore arrangement to form interconnected pore structures remain unclear. In particular, the correlation between framework thickness (distance between pores) or macroporosity and the diffusion of gaseous reactants to achieve a high catalytic performance has not been extensively discussed. Here, the interconnected pore structure was successfully controlled by adjusting the precursor components (i.e., template particle concentration) via a template-assisted spray process. A cross-sectional image analysis was conducted to comprehensively examine the internal structure and porous properties (framework thickness and macroporosity) of the porous TWC particles. In addition, we propose mathematical equations to predict the framework thickness and macroporosity, as well as determine the critical conditions that caused the formation of interconnected pores and broken structures in the porous TWC particles. The evaluation of CO oxidation performance revealed that porous TWC particles with an interconnected pore structure, thin framework, and high macroporosity exhibited a high catalytic performance owing to the effective diffusion and utilization of their internal parts. The study findings provide valuable insights into the design of porous TWC particles with interconnected pore structures to enhance exhaust gas emission control in real-world applications.

Biomimetic Construction of Ferriporphyrin‐Based Porous Catalysts for Boosting Nitrogen Electroxidation to Nitrate

AbstractElectrocatalytic N2 oxidation reaction (NOR) is an environmentally sustainable approach to synthesize NO3− under mild conditions. Inspired by the ferriporphyrin (FePP) catalytic species in nitrite oxidoreductase, three FePP‐based biomimetic catalysts with different functional groups (─NH2, ─H, and ─COOCH3) are designed and prepared successfully. Theoretical calculations indicate that these functional groups can alter the electron density of Fe catalytic center, affecting their ability to adsorb and activate N2. The strong electron‐donating ability of ─NH2 group can enhance the electron density of iron sites, which reveals a maximum NO3− yield of 728.55 µmol h−1 gFePP−1 and a high Faradaic efficiency of 10.6%. After that, the optimized FePP molecules can be encapsulated into ZIF‐8, which remarkably promoted the N2─to─NO3− transformation with a NO3− production rate of 1767.74 µmol h−1 gFePP−1, achieving the highest catalytic effect among metalloporphyrin‐based molecular catalysts under mild conditions. This work develops an available biomimetic approach to modulate the electron distribution of active metal sites and confine catalytic species into porous crystalline materials for constructing high‐performance NOR electrocatalysts.

Be Aware of Transient Dissolution Processes in Co3O4 Acidic Oxygen Evolution Reaction Electrocatalysts.

Recently, cobalt-based oxides have received considerable attention as an alternative to expensive and scarce iridium for catalyzing the oxygen evolution reaction (OER) under acidic conditions. Although the reported materials demonstrate promising durability, they are not entirely intact, calling for fundamental research efforts to understand the processes governing the degradation of such catalysts. To this end, this work studies the dissolution mechanism of a model Co3O4 porous catalyst under different electrochemical conditions using online inductively coupled plasma mass spectrometry (online ICP-MS), identical location scanning transmission electron microscopy (IL-STEM), and differential electrochemical mass spectrometry (DEMS). Despite the high thermodynamics tendency reflected in the Pourbaix diagram, it is shown that the cobalt dissolution kinetics is sluggish and can be lowered further by modifying the electrochemical protocol. For the latter, identified in this study, several (electro)chemical reaction pathways that lead to the dissolution of Co3O4 must be considered. Hence, this work uncovers the transient character of cobalt dissolution and provides valuable insights that can help to understand the promising stability of cobalt-based materials in already published works and facilitate the knowledge-driven design of novel, stable, abundant catalysts toward the OER in an acidic environment.

Enhancing Ammonia Synthesis and CO Hydrogenation to Methanol via Nonthermal Plasma Catalysis: A Focus on Catalyst Pore Structure and Active Site Design

The increasing energy demand, climate change and sustainable development necessitate the transition from fossil fuels to renewable sources (such feedstock and energy). Green hydrogen is one of the key components in sustainable energies/fuels being crucial for reducing carbon emissions and achieving carbon neutrality. However, hydrogen storage and transportation are challenging, and chemical hydrogen storage reactions such as ammonia synthesis and CO2 hydrogenation (to methanol) are considered promising solutions. Nonthermal plasmas (NTPs) are partially ionized gases with various energetic species, which are produced under ambient conditions being able to facilitate efficient chemical reactions under mild conditions. Importantly, NTP technologies can theoretically utilize green electricity produced by renewable energies (such as solar and wind) showing significant low-carbon potential. Previous studies have shown the catalysts design has an important impact on the performance of catalytic reactions under NTP conditions, and hence this aspect deserves attention. Here this mini review comments on the application of NTP catalytic technologies in ammonia synthesis and CO2 hydrogenation to methanol, with a special focus on catalyst pore structure and active site design. The critical summary and perspective can serve as the most current snapshot of the relevant research fields in NTP technologies, helping their further development.

A semi-analytical solution of a nonlinear boundary value problem arises in porous catalysts.

A semi-analytical solution of a nonlinear boundary value problem arises in porous catalysts.

Silver Nanoparticles Incorporated Covalent Organic Framework Catalyzed Sustainable Synthesis of Cyclic Carbonates and Oxazolidinones Under Atmospheric CO2 Pressure: A Novel Approach of CO2 Utilization

AbstractThis work presents the facile synthesis of Ag nanoparticles‐decorated porous crystalline covalent organic frameworks (namely, Ag@TPT‐TP COF) having exceptional surface area and CO2 uptake capacity to facilitate CO2‐cyclization reactions to produce highly value‐added compounds. Several characterization techniques have been used to thoroughly analyze the as‐synthesized nanomaterial, Ag@TPT‐TP COF. The synthesized Ag NPs‐embedded 2D COF serves as a stable and active porous catalyst for the synthesis of cyclic carbonates from a variety of epoxides and derivatives of 2‐oxazolidinone from propargyl alcohols and amines with high yield and selectivity of the corresponding products via fixation of CO2 (1 atm) under sustainable reaction conditions. The functionalized porous catalyst (Ag@TPT‐TP COF) exhibited exceptional recyclability for both reactions up to six consecutive runs without any visible deterioration in the catalytic activity. Consequently, formation of wide range of compounds are dramatically expanded by these organic transformations and provide a possible pathway for CO2 functionalization to get beyond the energy barrier in this area.

A Porous Copper Catalyst for Electrochemical Nitrate Reduction to Ammonium

A Porous Copper Catalyst for Electrochemical Nitrate Reduction to Ammonium

Design and internal structure analysis of submicron aggregated and porous three-way catalyst particles synthesized via spray drying for enhanced CO conversion

Design and internal structure analysis of submicron aggregated and porous three-way catalyst particles synthesized via spray drying for enhanced CO conversion

Synthesis of hierarchically porous tantalum phosphate catalysts by a sol–gel method for transformation of glucose to 5-hydroxymethylfurfural

A hierarchically porous and highly effective tantalum phosphate (TaP) solid acidic catalyst was synthesized using a sol–gel method accompanied by phase separation for converting glucose to 5-hydroxymethylfurfural (HMF).

An efficient porous carbon catalyst derived by Cobalt-MOF precursor for degrading antibiotics in aqueous system

An efficient porous carbon catalyst derived by Cobalt-MOF precursor for degrading antibiotics in aqueous system

Heterogeneous Iridium(III) conjugated porous polymer photoredox catalyst based on BODIPY

Heterogeneous Iridium(III) conjugated porous polymer photoredox catalyst based on BODIPY

Building a Co-Salen-Immobilized Porous Organic Polymer Catalyst for CO2 Cycloaddition.

The CO2-epoxide addition to cyclic carbonate is of great significance but usually requires high temperatures and CO2 pressures. Herein, a spirobifluorene-based porous organic polymer catalyst is designed with a Co-salen complex immobilized on the backbone (ST-CoSalen-POP) to enable CO2 fixation under mild conditions. ST-CoSalen-POP possesses a high Co-loading content (9.35 wt%), a large pore volume, and high CO2 adsorption capacity. This catalyst achieves a 96% yield in the cycloaddition of CO2 with epoxides at 25°C and 0.1MPa CO2 pressures. Moreover, ST-CoSalen-POP also offers the advantages of wide adaptability over epoxide substrates and high structural stability for three consecutive cycles. This study presents a novel catalytic approach for promoting CO2 fixation, offering a significant advancement in the efficient synthesis of fine chemicals.

The Synthesis, Characteristics, and Application of Hierarchical Porous Materials in Carbon Dioxide Reduction Reactions

The reduction of carbon dioxide to valuable chemical products could favor the establishment of a sustainable carbon cycle, which has attracted much attention in recent years. Developing efficient catalysts plays a vital role in the carbon dioxide reduction reaction (CO2RR) process, but with great challenges in achieving a uniform distribution of catalytic active sites and rapid mass transfer properties. Hierarchical porous materials with a porous hierarchy show great promise for application in CO2RRs owing to the high specific surface area and superior porous connection. Plenty of breakthroughs in recent CO2RR studies have been recently achieved regarding hierarchical porous materials, indicating that a summary of hierarchical porous materials for carbon dioxide reduction reactions is highly desired and significant. In this paper, we summarize the recent breakthroughs of hierarchical porous materials in CO2RRs, including classical synthesis methods, advanced characterization technologies, and novel CO2RR strategies. Moreover, by highlighting several significant works, the advantages of hierarchical porous materials for CO2RRs are analyzed and revealed. Additionally, a perspective on hierarchical porous materials for CO2RRs (e.g., challenges, potential catalysts, promising strategies, etc.) for future study is also presented. It can be anticipated that this comprehensive review will provide valuable insights for further developing efficient alternative hierarchical porous catalysts for CO2 reduction reactions.

In/Outside Catalytic Sites of the Pore Walls in One-Dimensional Covalent Organic Frameworks for Oxygen Reduction Reaction.

Pore channels play a decisive role in mass transport in catalytic systems. However, the influences of the location of catalytic sites inside or outside of the pore walls on the performance were still under-explored due, because it is difficult to construct sites anchored in or outside of pore walls. Herein, one-dimensional covalent organic frameworks with precisely anchored active sites were used to explore the effects of channels on a typical oxygen reduction reaction (ORR) catalysis. Electrocatalytic evaluations showed that single Pt sites located inside of the channels exhibited higher kinetic activity compared to those anchored outside. The in situ spectroscopic analysis revealed that local reconstruction of Pt-Cl breaking and potential-induced anion transport occurred more effectively inside the channels. The superior anion transportability and kinetic activity of the inside-channel active sites also facilitated *OH desorption during the ORR process outperforming their outside-channel counterparts. The results of this study provide strategies for designing active sites in porous catalysts for heterogeneous catalysis.

Constructing Highly Porous Low Iridium Anode Catalysts Via Dealloying for Proton Exchange Membrane Water Electrolyzers.

Iridium (Ir) is the most active and durable anode catalyst for the oxygen evolution reaction (OER) for proton exchange membrane water electrolyzers (PEMWEs). However, their large-scale applications are hindered by high costs and scarcity of Ir. Lowering Ir loadings below 1.0 mgcm-2 causes significantly reduced PEMWE performance and durability. Therefore, developing efficient low Ir-based catalysts is critical to widely commercializing PEMWEs. Herein, an approach is presented for designing porous Ir metal aerogel (MA) catalysts via chemically dealloying IrCu alloys. The unique hierarchical pore structures and multiple channels of the Ir MA catalyst significantly increase electrochemical surface area (ECSA) and enhance OER activity compared to conventional Ir black catalysts, providing an effective solution to design low-Ir catalysts with improved Ir utilization and enhanced stability. An optimized membrane electrode assembly (MEA) with an Ir loading of 0.5 mgIr cm-2 generated 2.0 A cm-2 at 1.79V, higher than the Ir black at a loading of 2.0 mgIr cm-2 (1.63 A cm-2). The low-Ir MEA demonstrated an acceptable decay rate of ≈40 µV h-1 during durability tests at 0.5 (>1200 h) and 2.0 A cm-2 (400 h), outperforming the commercial Ir-based MEA (175 µV h-1 at 2.0 mgIr cm-2).

In/Outside Catalytic Sites of the Pore Walls in One‐Dimensional Covalent Organic Frameworks for Oxygen Reduction Reaction

Pore channels play a decisive for mass transport in catalytic systems. However, the influences of the location of catalytic sites inside or outside of the pore walls on the performance were still under‐explored due, because it is difficult to construct sites anchored in or outside of pore walls. Herein, one‐dimensional covalent organic frameworks (COFs) with precisely anchored active sites were used to explore the effects of channels on a typical oxygen reduction reaction (ORR) catalysis. Electrocatalytic evaluations showed that single Pt sites located inside of the channels exhibited higher kinetic activity compared to those anchored outside. The in situ spectroscopic analysis revealed that local reconstruction of Pt–Cl breaking and potential‐induced anion transport occurred more effectively inside the channels. The superior anion transportability and kinetic activity of the inside‐channel active sites also facilitated *OH desorption during the ORR process outperforming their outside‐channel counterparts. The results of this study provide strategies for designing active sites in porous catalysts for heterogeneous catalysis.

MnO2 Nanowire Thin Mesh With Enhanced Mass Transfer as Hydroxide Exchange Membrane Fuel Cell Cathode

AbstractHydroxide exchange membrane fuel cells (HEMFCs) are promising due to the potential use of nonprecious metal catalysts. However, the performance of HEMFCs based on nonprecious catalysts is still unsatisfactory, and one reason for this is hindered mass transfer in the catalyst layer. In this study, we employ a hydrothermal method to grow in situ a MnO2 nanowire thin mesh (NTM) catalytic layer on the gas diffusion electrode. The HEMFC prepared with MnO2 NTM cathode achieves a peak power density of 425 mW cm−2, surpassing the performance of the HEMFC prepared using the traditional powder catalyst spraying method by four times. High‐frequency resistance and limiting current tests indicate that the MnO2 NTM reduces ohmic resistance and improves mass transfer, thereby enhancing the HEMFC performance. Furthermore, the peak power density of the HEMFC is increased to 626 mW cm−2 by depositing additional active Co3O4 nanoparticles on the MnO2 NTM. These findings demonstrate that an interconnected and porous catalyst layer structure is beneficial for improving mass transfer properties, which in turn enhances HEMFC performance.

Surfactant-modified ZnFe2O4/CaOPS porous acid-base bifunctional catalysts for biodiesel production from waste cooking oil and process optimization

Biodiesel production from waste cooking oil (WCO) with high acid value is useful for clean energy development and utilization. In this work, ZnFe2O4(5)/CaOPS porous bifunctional catalysts were prepared for catalytic production of biodiesel with the help of surfactants such as PVP, SDS and citric acid, using a sol-gel method. The ZnFe2O4(5)/CaOPS catalysts were characterized using XRD, SEM, EDX, NH3-TPD, and BET. The parameters (reaction temperature, catalyst dosage, methanol-oil ratio and reaction time) for the transesterification reaction to produce fatty acid methyl esters (FAMEs) were optimized for the optimal materials using a one-variable method. Experiments were designed using Response Surface Methodology (RSM) and Artificial Neural Network (ANN) for global optimization to obtain the best process parameters. The final average yield of FAMEs was 96.89% under the optimum reaction parameter of catalyst dosage of 5.06wt%, reaction temperature of 63.69°C, reaction time of 212.22min and methanol-oil ratio of 12.96:1. The prepared biodiesel was characterized using FT-IR, 1H NMR as well as 13C NMR and compared with international standard ASTM D6751. The ZnFe2O4(5)/CaOPS catalyst has excellent stability in biodiesel production and has some free fatty acid tolerance. In addition, a cost analysis and sensitivity analysis were done for the production of WCO biodiesel. It is hoped that the research results in this paper can provide a theoretical basis for biodiesel production from WCO with high free fatty acid content.