Dispersed Ag Nanoparticles Research Articles

Ag Nanoparticles-Confined Doped within Triazine-Based Covalent Organic Frameworks for Syngas Production from Electrocatalytic Reduction of CO2.

Electrocatalytic CO2 reduction reaction (CO2RR) emerges as a promising avenue to mitigate carbon emissions, enabling the capture and conversion of CO2 into high-value products such as syngas with CO/H2. One of the crucial aspects lies in the tailored development of durable and efficient electrocatalysts for the CO2RR. Covalent organic frameworks (COFs) possess unique characteristics that render them attractive candidates for catalytic applications. However, the relationship between structure and performance still requires further exploration; especially, most COFs with such properties are limited to COFs containing specific groups such as phthalocyanine or porphyrin groups. Here, we custom-synthesize two azine-linked nitrogen-rich COFs constructed from triazine building blocks, which are doped with ultrafine and highly dispersed Ag nanoparticles (Ag@TFPT-HZ and Ag@TPT-HZ). Thus-obtained COFs can serve as electrocatalysts for the CO2RR, and a comprehensive investigation has been conducted to uncover the intricate structure-performance relationship within these materials. Notably, Ag@TFPT-HZ exhibits superior CO selectivity in the electrocatalytic CO2RR, achieving a FECO of 81% and a partial current density of 7.65 mA·cm-2 at the potential of -1.0 V (vs reversible hydrogen electrode (RHE)). In addition, Ag@TPT-HZ as an electrocatalyst can continuously produce syngas with a CO/H2 molar ratio of 1:1, an ideal condition for methanol synthesis. The observed distinct performance between these two COFs is attributed to the presence of O atoms in TFPT-HZ. These O atoms facilitate a higher loading capacity of Ag nanoparticles (11 wt %) and generate a greater number of active sites, thereby enhancing electrochemical activity and promoting faster reaction kinetics. Therefore, two tailor-made two-dimensional (2D) nitrogen-rich COFs with various active sites as electrocatalysts can exhibit different outstanding electrocatalytic performances for CO2RR and possess high cycling stability (>50 h). This work offers valuable insights into the design and synthesis of electrocatalysts, particularly in elucidating the intricate relationship between their structure and performance.

Enhanced sonophoto-catalytic and adsorption capabilities of Fe3O4@MC/MWCNT-CuO/Ag for petrochemical organic pollutants degradation from industrial process streams

To address the problem of petrochemical organic pollutants in water, specifically monoethylene glycol (MEG) present in industrial process streams, in this research, we synthesized and evaluated a multifunctional nanocomposite, Fe3O4@MC/MWCNT-CuO/Ag. The nanocomposite was produced by combining magnetic Fe3O4 nanoparticles, methylcellulose (MC), multi-walled carbon nanotubes (MWCNTs), and CuO/Ag nanoparticles by an integrated synthesis process. A consistent dispersion of nanoparticles, with diameters ranging from 30-40 nm, was discovered by FESEM analysis, showing effective integration without aggregation. Effective synthesis was demonstrated by well-doped and evenly dispersed CuO and Ag nanoparticles. Functional groups that improve electrostatic interactions with contaminants hence enhancing catalytic performance and adsorption efficiency, were validated by FTIR analysis. XRD indicated an unchanged crystal structure with an average crystallite size of 8.67 nm. The anticipated elemental composition was verified by EDS & mapping. A VSM study revealed magnetic characteristics (9.33 emu/g) that simplify nanocomposite separation and reuse. TGA proved thermal stability to be up to 600 °C. A BET study showed a highly specific surface area of 67.661 m2/g, enhancing adsorption. According to DRS and PL studies, the bandgap was lowered by 1.31 eV, which led to better optical absorption. The nanocomposite exhibited notable MEG removal efficiency, with 72 % in adsorption, 65 % in photocatalysis, and 56 % in sonocatalysis. This makes it a promising alternative for the remediation of organic pollutants in water treatment.

Mechanisms of mercury removal from water with highly efficient MXene and silver-modified polyethyleneimine cryogel composite filters

Safeguarding aquatic ecosystems and human health requires effective methods for removing pollutants. Mercury (Hg) is a very toxic pollutant with a global presence and is highly mobile and persistent. Here, innovative materials were prepared for separating Hg(II) from water, and the mechanisms underlying the efficient uptake of Hg species have been investigated. The sorbents include silver (Ag) nanoparticles and multilayered Ti3C2Tx MXene, both incorporated into the structure of a three-dimensional polyethyleneimine porous cryogel (PEI) that acts as a scaffold holding and exposing nano active sites involved in the removal of Hg. Specifically, Ag particles were deposited onto MXene phases, and the resulting composite was embedded in the macroporous PEI polymer (PEI/MXene@Ag cryogel). The composite has beneficial properties regarding Hg removal: 99% of Hg was separated from waste within 24 h in batch studies. The maximum removal capacity of Hg reached 875 mg/g from HgCl2, and 761 mg/g and 1280 mg/g from Hg(OAc)2 and Hg(NO3)2 salts by PEI/MXene@Ag. The Hg uptake stems from the composite’s relatively large specific surface area, layered porous channels, and highly dispersed Ag nanoparticles in the multilayered Ti3C2Tx MXene. The matrix in the water samples that were treated with the composite did not hinder the uptake of Hg by PEI/MXene@Ag. The high effectiveness achieved for the removal of Hg, combined with rapid adsorption kinetics, high efficiency, and selectivity, positions it as an efficient solution. Future work should address upscaling its preparation for increasing readiness towards mitigating Hg in surface water.

Modulating the Electrocatalytic CO2-CO Performance by Ag Morphology

Highly selective conversion of CO2 into CO molecules remains a major challenge in electrocatalytic CO2 reduction reactions, and metallic silver-based materials have great potential. However, the selectivity and activity of traditional silver (Ag)-based materials cannot reach the desired level, and the development of new Ag-based materials has become a hot research topic. Here, novel ag-glomerated spore-shaped Ag nanomaterials are reported for the efficient reduction of CO2 to CO. The unique nanostructures endowed with larger specific surface area, and the spore-like dispersed Ag nanoparticles (NPs) have more unsaturated Ag sites, which endowed the catalysts with higher intrinsic activity. Electrochemical tests show that spore-like Ag can obtain a Faraday efficiency (FE) of 95.6% at −1 V vs RHE, which is much higher than that of Ag nanowires (NWs) (73%) and ordinary Ag NPs (83%) synthesized in the same period. By using the three different morphologies of Ag synthesized as a research platform and statistically comparing the FE in the corresponding voltage interval, we obtained the influence of morphology effect on the selectivity of CO product production by electrocatalytic CO2 production over Ag-based catalysts, which can be further used as a guideline for catalyst development.

Atomic level dispersed nickel coupled with silver nanoparticle to boost the efficiency of CO2 conversion to CO via spin electrons regulation

Modulating the electronic configuration by coupling multi-scale active sites for electrocatalytic conversion of CO2 to CO is extremely challenging in terms of structural analysis and mechanism elucidation. Herein, a catalyst NiAD/AgNPs@CN with both atomic-level dispersed Ni and Ag nanoparticles on N-doped carbon substrate has been designed to reveal the true active sites and catalytic mechanism in complex materials. NiAD/AgNPs@CN exhibits CO Faraday efficiency (FECO) of 99.97% at −0.88 V (vs. RHE) in H-type cell and 91.77% FECO with a high current density of 79.70 mA/cm2 in flow cell. DFT calculations show that the tiny change in the energy level of spin electrons at atomic sites has a significant impact on the CO2 activation. The regulation of atomic Ni on Ag sites is the main reason for improving CO2RR performance. This work gives a new understanding on the catalytic mechanism of composite materials structured by atomic-level dispersed metal and nanoparticles.

Ultradeep Removal of Acetaldehyde from Ethanol through Catalytic Hydrogenation with Highly Dispersed Ag Nanoparticles Supported on Phenyl-Modified SiO2

Ultradeep Removal of Acetaldehyde from Ethanol through Catalytic Hydrogenation with Highly Dispersed Ag Nanoparticles Supported on Phenyl-Modified SiO₂

SYNTHESIS, CHARACTERIZATION OF CeO2@Ag HOLLOW SPHERES AND EVALUATION OF THEIR CATALYST ACTIVITY FOR THE REDUCTION OF 4-NP

A CeO2@Ag hollow spherical composite catalyst was synthesized with the template method. Firstly, a SiO2@CeO2 core-shell structure was synthesized using SiO2 spheres as the template, and then the SiO2 core was removed by etching to obtain hollow CeO2 spheres. The CeO2 hollow microspheres have a large specific surface area, which can effectively suppress the aggregation of Ag nanoparticles, leading to CeO2@Ag with a regular morphology and well dispersed Ag nanoparticles. There is a strong synergistic effect between CeO2 and Ag, which is beneficial to improving the catalytic performance. As a result, the CeO2@Ag hollow spherical composite catalyst can reduce 4-nitrophenol efficiently.

Hollow Starlike Ag/CoMo-LDH Heterojunction with a Tunable d-Band Center for Boosting Oxygen Evolution Reaction Electrocatalysis.

It is a challenging task to utilize efficient electrocatalytic metal hydroxide-based materials for the oxygen evolution reaction (OER) in order to produce clean hydrogen energy through water splitting, primarily due to the restricted availability of active sites and the undesirably high adsorption energies of oxygenated species. To address these challenges simultaneously, we intentionally engineer a hollow star-shaped Ag/CoMo-LDH heterostructure as a highly efficient electrocatalytic system. This design incorporates a considerable number of heterointerfaces between evenly dispersed Ag nanoparticles and CoMo-LDH nanosheets. The heterojunction materials have been prepared using self-assembly, in situ transformation, and spontaneous redox processes. The nanosheet-integrated hollow architecture can prevent active entities from agglomeration and facilitate mass transportation, enabling the constant exposure of active sites. Specifically, the powerful electronic interaction within the heterojunction can successfully regulate the Co3+/Co2+ ratio and the d-band center, resulting in rational optimization of the adsorption and desorption of the intermediates on the site. Benefiting from its well-defined multifunctional structures, the Ag0.4/CoMo-LDH with optimal Ag loading exhibits impressive OER activity, the overpotential being 290 mV to reach a 10 mA cm-2 current density. The present study sheds some new insights into the electron structure modulation of hollow heterostructures toward rationally designing electrocatalytic materials for the OER.

Ag/Reduced Graphene Oxide/Carbon Fiber Composites as Electrodes for Highly Stable and Responsive Marine Electric Field Sensors

The increasing demand for maintenance-free, cost-effective, and high-stability flexible electrodes is highly anticipated for the research of marine electric-field sensors, and various carbon fibers (CFs) are considered the most suitable carbon-based electrode for the purpose. Nevertheless, the conventional fabrication of acidified or nitrogenized CF electrodes did not attract great attention for commercial application, which has limitations in the case of simultaneous cost-effectiveness and long-term stability. In this study, with homemade reduced graphene oxide (rGO) load, the prepared double carbon substrate Ag-rGO-CF composite electrodes have a honeycomb rGO conductive skeleton and the dispersed Ag nanoparticles via a facile hermetic oxidation process and hydrothermal method. The prepared Ag-rGO-CF composite electrode demonstrated an outstanding electrode performance, including low resistance, high electrochemical reaction rate, and stable potential with long-term stability and low cost. The electric double-layer (EDL) structure theory from the Gouy–Chapman–Stern model and double carbon substrate mechanism between CFs and rGO with the help of Ag were clarified, whose principle is to strengthen the adsorption force and electrostatic attraction of the electrode and to offset the residual charge while reducing the thickness of the electric double layer to achieve the purpose of potential balance. The Ag-rGO-CF composite electrode has presented long-term stability and high sensitivity, especially a wide application bandwidth. The Ag-rGO-CF composite electrode made in this study is a competitive candidate material as a flexible marine electrode field sensor.

Highly conductive Ag-SiNx composite thin film anode engineering for transparent battery

Silicon nitride-based electrodes (SiNx), have been proposed as promising candidates for high-capacity transparent anode electrodes in earlier studies. Unfortunately, they have low electrical conductivity, resulting in some disadvantages such as power density for application in thin film batteries. To improve electrical conductivity, bulk batteries use conductive carbon additives, which also impair transmittance. Thus, we conducted this research to enhance the electrochemical properties by improving the conductivity without compromising the transmittance by uniformly dispersed Ag nanoparticles in SiNx thin film. We obtained an Ag-SiNx composite thin-film anode via continuous composition spread sputtering and investigated the effect of the Ag concentration. The capacity of the thin-film battery raised to 242.8 μAh/cm2·μm with Ag0.236SiO0.7N anode compared to the SiO0.7N anode which had a capacity of 37.2 μAh/cm2·μm. In addition, while SiO0.7N was operated only up to 2 C, Ag0.236SiO0.7N has driven up to 5 C and 10 C, which are high C rates, was also possible. AgxSiO0.7N thin film with less than 0.236 mol content demonstrates an optical transmittance of over 60% in the visible area. These results indicate that improving the electrical conductivity by the addition of an Ag during the silicon nitride deposition can increase its electrochemical performance while maintaining its applicability to transparent batteries.

Novel ZnO/Ag nanohybrids prepared from Ag+-doped layered zinc hydroxides as highly active photocatalysts for the degradation of dyes and Ciprofloxacin

The design and the synthesis of highly active nanohybrid photocatalysts for environmental remediation is a topical issue in the context of sustainable development. The hybridization of a semiconductor with noble metal nanoparticles (NPs) has been demonstrated to be a versatile strategy to restrict the recombination of photogenerated electron-hole pairs and thus increase the photocatalytic activity. However, the uniform association of nanosized metal particles with ZnO NPs remains a challenge. Herein, a novel synthesis of ZnO NPs hybridized with Ag(0) NPs is presented. Ag+-doped layered zinc hydroxides (LZHs) were prepared in aqueous solution in the presence of triethanolamine and subsequently Ag+ ions were photoreduced into metallic Ag NPs embedded into LZHs. The LZHs not only promote the dispersion of Ag NPs but also limit their growth. The Ag(0)-doped LZHs obtained after hydrothermal treatment was finally transformed into ZnO/Ag nanohybrids by a mild thermal treatment at 300 °C for 5 min, which allows high interface coupling between ZnO and Ag NPs. ZnO associated with 3 mol% Ag exhibits the highest photocatalytic activity for the degradation of dyes (Rhodamine B and Remazol Brillant Blue R) and of the Ciprofloxacin antibiotic. The high photocatalytic performance of the ZnO/Ag(3) nanohybrid originates from the charge transfer in the ZnO/Ag nanohybrid and from the enhanced harvesting of visible light. The ZnO/Ag(3) photocatalyst also exhibits a high practical stability, indicating its great potential for real photocatalytic applications.

Silver Ion-Exchanged Anionic Metal–Organic Frameworks for Iodine Adsorption: Silver Species Evolution from Ions to Nanoparticles

Ag clusters and nanoparticles have attracted much attention in the fields of environmental catalysis and pollutant removal. It is a common strategy to fabricate highly dispersed Ag nanoparticles in porous scaffolds via in situ growth. Here, anionic metal–organic frameworks (MOFs) have been employed to provide robust supports for Ag species. Ag nanoparticles with well-defined sizes are observed in MOFs when internal NH2Me2+ is exchanged with extrinsic Ag+ ions. The extended X-ray absorption fine structure and X-ray photoelectron spectroscopy spectra confirm that about 20% of Ag+ are reduced into Ag0, while the rest 80% are still Ag+ species. The comparison of Ag loading into anionic and neutral Cu-BTC MOFs suggests that the exchangeable cations facilitate Ag+ migration into the interior of MOFs and thus alleviate its aggregation and spontaneous reduction. Besides, the adsorption tests verify that all the Ag species in MOFs are accessible to iodine vapor to form AgI. The charge transfer from frameworks to trapped iodine and the water in the air promote the formation of iodide ions, which react with Ag+ to produce AgI. The iodine adsorption performance of MOF beads was also evaluated using the pore diffusion model. This work provides insights into the evolution of Ag species in MOFs and potential Ag-based adsorbents for radioiodine capture.

Dispersion and Homogeneity of MgO and Ag Nanoparticles Mixed with Polymethylmethacrylate.

This study aims to examine the impact of the direct and indirect mixing techniques on the dispersion and homogeneity of magnesium oxide (MgO) and silver (Ag) nanoparticles (NPs) mixed with polymethylmethacrylate (PMMA). NPs were mixed with PMMA powder directly (non-ethanol-assisted) and indirectly (ethanol-assisted) with the aid of ethanol as solvent. X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscope (SEM) were used to evaluate the dispersion and homogeneity of MgO and Ag NPs within the PMMA-NPs nanocomposite matrix. Prepared discs of PMMA-MgO and PMMA-Ag nanocomposite were analyzed for dispersion and agglomeration by Stereo microscope. XRD showed that the average crystallite size of NPs within PMMA-NP nanocomposite powder was smaller in the case of ethanol-assisted mixing compared to non-ethanol-assisted mixing. Furthermore, EDX and SEM revealed good dispersion and homogeneity of both NPs on PMMA particles with ethanol-assisted mixing compared to the non-ethanol-assisted one. Again, the PMMA-MgO and PMMA-Ag nanocomposite discs were found to have better dispersion and no agglomeration with ethanol-assisted mixing when compared to the non-ethanol-assisted mixing technique. Ethanol-assisted mixing of MgO and Ag NPs with PMMA powder obtained better dispersion, better homogeneity, and no agglomeration of NPs within the PMMA-NP matrix.

Functionalized agarose hydrogel with in situ Ag nanoparticles as highly recyclable heterogeneous catalyst for aromatic organic pollutants.

In the present research work, a highly recyclable catalyst of Ag-based agarose (HRC-Ag/Agar) hydrogel was successfully fabricated through a simple and efficient in situ reduction method without the aid of additional surface active agent. The interaction between the rich hydroxyl functional (-OH) groups in agarose and Ag can effectively control the growth and dispersion of Ag nanoparticles (NPs) in the HRC-Ag/Agar hydrogel and keep Ag NPs free from chemical contamination, which also guarantees the reusability of HRC-Ag/Agar hydrogel as catalysts. HRC-Ag/Agar hydrogel without freeze drying and calcination was investigated for their potential applications as highly active/recyclable catalysts in reducing aromatic organic pollutants (p-nitrophenol (4-NP), methylene blue (MB) and rhodamine B (RhB)) by KBH4. The optimal HRC-Ag/Agar-1.9 hydrogel can complete the catalytic reduction of 4-NP within 11min. Moreover, HRC-Ag/Agar-1.9 hydrogel achieves the high conversion rate (> 99%) through ten catalytic runs. Similarly, HRC-Ag/Agar-1.9 hydrogel was able to achieve a reduction efficiency of RhB at 98% within 17min and that of MB at 95% within 40min. The advantages of simple synthetic procedure, no secondary pollution, strong stability and easily separated make the HRC-Ag/Agar hydrogel have great potential prospect for environmental applications.

Engineering Triboelectric Charge in Natural Rubber-Ag Nanocomposite for Enhancing Electrical Output of a Triboelectric Nanogenerator.

An environmentally friendly triboelectric nanogenerator (TENG) is fabricated from a natural rubber (NR)-Ag nanocomposite for harvesting mechanical energy from human motions. Ag nanoparticles (AgNPs) synthesized with two different capping agents are added to NR polymer for improving dielectric constant that contributes to the enhancement of TENG performance. Dielectric constant is modulated via interfacial polarization between AgNPs and NR matrix. The effects of AgNP concentration, particle size and dispersion in NR composite, and type of capping agents on dielectric properties and electrical output of the NR composite TENG are elucidated. It is found that, apart from AgNPs content in the NR-Ag nanocomposite, cations of CTAB capping agent play important roles not only on the dispersion of AgNPs in NR matrix but also on intensifying tribopositive charges in the NR composite. In addition, the application of the NR-Ag TENG as a shoe insole is also demonstrated to convert human footsteps into electricity to power small electronic devices. Furthermore, with the presence of Ag nanoparticles, the fabricated shoe insole also exhibits antibacterial property against Staphylococcus aureus that causes foot odor.

Efficient electrocatalytic reduction of CO2 to CO on highly dispersed Ag nanoparticles confined by Poly(ionic liquid)

Efficient electrocatalytic conversion of CO2 to CO is a promising mode for CO2 transformation driven by renewable electricity. Herein, varied poly(ionic liquid)-Ag (PIL-Ag) hybrids are facilely synthesized by impregnating chloride-based PIL with silver salts. The remarkable confinement effect of PIL on the patterns of in-situ formed highly dispersed Ag–Cl species leads to the corresponding complexes, clusters, and nanoparticles (NPs) in the inner domain, while their distribution is highly correlated to both microstructures of the PIL skeleton and silver salts launched. As a result, the highly dispersed imidazolium-pyridine-imidazolium tridentate sites at the PIL layer combined with a compatible supply rate of Ag+ cation enables the formation of abundant AgCl NPs in PIL-Cl@AgOAc-1.0, which provided a high CO selectivity of 96.8 % with a high partial current density of 207.0 mA cm−2 at –0.91 V (vs RHE) in 1 M KOH. Besides, long-term electrolysis was conducted at 100 mA cm−2 for 100 h with a slight decay of selectivity to ∼ 86 %. Further, despite the similar intrinsic activity of three Ag–Cl species, the patterns of Ag–Cl species, the number of active sites, and the mass transfer of reactants within the hybrids jointly determine the apparent electrocatalytic performance obtained at high rates.

Tribological Properties of Polydopamine-Modified Ag as Lubricant Oil Additives

Nanoparticles agglomerate easily because of their high surface energy, which seriously reduces their tribological properties as lubricant additives. In this work, the core-shell nanoparticles Ag@polydopamine (PDA) were successfully prepared by the self-oxidation of dopamine hydrochloride on the surface of Ag nanoparticles and the dispersion of Ag nanoparticles in PAO6 was improved to promote anti-wear behaviors. The tribological properties of Ag@PDA nanocomposites as additives in poly alpha olefin (PAO) oil were studied under different concentrations, pressure and speed conditions by UMT-5 tribometer. It was demonstrated that the strong electrostatic repulsion of the PDA structure made the Ag nanoparticles better dispersed in PAO oil, thus playing a better lubricating role. When the concentration of the modified nanoparticles was 0.25 wt%, the friction coefficient of the lubricating oil decreased by 18.67% and no obvious wear was observed on the friction pair surface. When the Ag@PDA content was higher than 0.25 wt%, the tribological performance of the lubricating oil was weakened, which may be due to excessive Ag@PDA acting as an abrasive on the friction surface, thereby increasing friction and wear. The friction coefficient of the lubricating oil containing Ag@PDA decreased with the increase in load, but hardly changed with the increase in frequency.

Palygorskite Supporting Homogeneously Dispersed Ag Nanoparticles: Molten Salt Method and Enhanced Antibacterial Performance

AbstractSupported silver nanoparticles (Ag NPs) have been used extensively as antibacterial agents in biomedicine, biotechnology, and environmental remediation. However, a facile and scalable method for preparing Ag NPs dispersed homogeneously on supports remains a challenge. In this study, a novel molten salt method was developed successfully to synthesize the supported, homogeneously dispersed Ag NPs on palygorskite. Abundant pores and ample surface hydroxyl groups of palygorskite served as anchoring sites, preventing the rapid growth, aggregation, and sintering of Ag NPs. Typically, palygorskite was mixed with AgNO3 (as a precursor) and NaNO3 (as a dispersant), and then the mixture was heated slowly. During the heating process, the AgNO3 decomposed gradually into Ag NPs and the molten NaNO3 with a high concentration of ions dispersed the newly formed Ag NPs. The Ag NPs were dispersed homogeneously on the palygorskite and had very small particle sizes (~5.8 nm) even for a significant loading amount (~9 wt.%). As antibacterial agents, the Ag/palygorskite nanocomposites showed enhanced antibacterial activity, compared with those synthesized without the introduction of molten NaNO3. In addition, the key effect of the surface hydroxyl groups of palygorskite on the characteristics of the loaded Ag and the corresponding antibacterial activity were also elucidated. As such, the present work provided a novel and facile strategy for the synthesis, without a chemical reductant or surfactant, of supported, highly dispersed Ag NPs on clay minerals and this could have potential in the scalable production and practical application of Ag-based antibacterial materials.

Chitosan-promoted sepiolite supported Ag as efficient catalyst for catalytic oxidative degradation of formaldehyde at low temperature

The chitosan (CTs) modified high purity sepiolite (HP-Sep) supported Ag nanoparticles catalyst (CTs-Ag/HP-Sep) was prepared by impregnation and applied in the catalytic oxidation of HCHO. 5CTs-10Ag/HP-Sep-300 (5 and 10 represent the weight percentage of 5% chitosan and 10% Ag, and 300 represents the calcination temperature of 300 °C) with abundant amino and hydroxyl groups, smaller highly dispersed metallic Ag nanoparticles presented superior adsorbability of HCHO and better oxidative degradation performance. The 100 ppm HCHO under the GHSV of 6000 mL/g·h can be completely oxidized to H2O and CO2 at low temperature of 52 °C. The addition of CTs was conducive to the HCHO adsorption, the formation of smaller Ag nanoparticles with lattice oxygen and the transformation of formate into carbonate species, hence promoting the HCHO oxidative degradation. The possible reaction route was discussed in detail based on the results of XPS and in-situ DRIFTS. This study will provide a promising way for designing highly efficient heterogeneous catalysts by combining nature clay with polymers supported active metal for the oxidative degradation of HCHO at low temperature.

Green carboxylation of CO2 triggered by well-dispersed silver nanoparticles immobilized by melamine-based porous organic polymers

CO2 fixation via directly formation of C-C bonds to obtain carboxylation compound is an essential reaction in industry. Creating efficient, inexpensive and industrially valuable key catalysts have always been a desire, but also an urgent challenge. Here, we synthesized a kind of melamine-based porous organic polymers (POPs) evenly loaded Ag Nanoparticles (Ag NPs/Melamine-based POPs) by the gas bubbling-assisted membrane reduction (GBMR) approach. The melamine-based POPs were used as good nitrogen-rich supports for loading and dispersing Ag nanoparticles. Ag NPs/ melamine-based POPs exhibited good CO2 absorption capacity (2.1 mmol/g, 273 K and 0.1 MPa) and the excellent activity was up to 93% towards the carboxylation of terminal alkynes with CO2 under mild reaction conditions (323 K, 0.1 MPa). And the TOF is 2.23 h−1. Specially, this is very few report of heterogeneously catalyzed directly formation of carboxylation compound only applying terminal alkynes with CO2 under low temperature and atmospheric pressure. The mechanistic study revealed that the well-dispersed Ag active species promoted highly efficient and green conversion of CO2. Moreover, the catalyst was easily recovered and could be reused at least six times with retention of high catalytic activity.