Quantitative Time-Resolved Visualization of Catalytic Degradation Reactions of Environmental Pollutants by Integrating Single-Drop Microextraction and Fluorescence Sensing.

Current methods for evaluating catalytic degradation reactions of environmental pollutants primarily rely on chromatography that often suffers from intermittent analysis, a long turnaround period, and complex sample pretreatment. Herein, we propose a quantitative time-resolved visualization method to evaluate the progress of catalytic degradation reactions by integrating sample pretreatment [single-drop microextraction, (SDME)], fluorescence sensing, and a smartphone detection platform. The dechlorination reaction of chlorobenzene derivatives was first investigated to validate the feasibility of this approach, in which SDME plays a critical role in direct sample pretreatment, and inorganic CsPbBr3 perovskite encapsulated in a metal-organic framework (MOF-5) was utilized as the fluorescent chromogenic agent (FLCA) in SDME to realize fast in situ colorimetric detection via the color switching from green (CsPbBr3) to blue (chlorine lead bromide, inorganic CsPbCl3 perovskite). The smartphone, which can calculate the B/G value of FLCA, serves as a data output window for quantitative time-resolved visualization. Further, a [Eu(PMA)]n (PMA= pyromellitic acid) fluorescent probe was constructed to use as an FLCA for the in situ evaluation of cinnamaldehyde and p-nitrophenol catalytic reduction. This approach not only minimizes the utilization of organic solvents and achieves quantitively efficient time-resolved visualization but also provides a feasible method for in situ monitoring of the progress of catalytic degradation reactions.

Direct Synthesis of Nanosheet-Stacked Hierarchical "Honey Stick-like" MFI Zeolites by an Aromatic Heterocyclic Dual-Functional Organic Structure-Directing Agent.

Soft template designing is the most promising strategy for the synthesis of zeolite nanosheets. MFI nanosheets directed by soft templates (containing long-chain alkyl groups or aromatic groups as hydrophobic component) can be found frequently; however, so far, MFI nanosheets synthesized by soft templates with aromatic heterocycle groups (e. g., s-triazine groups) are rare. Herein, a nanosheet-stacked hierarchical MFI zeolite (NSHM) has been synthesized by using a triply branched s-triazine-based surfactant as a bifunctional organic structure-directing agent. On the basis of a geometrical match relationship, a formation model has been proposed. Synthesized NSHM had abundant mesopores stacked by nanosheets and exhibited a high surface area (430 m2 ⋅ g-1 ). The 1 wt% Pd/NSHM attained a significant increase in yield of cyclohexanol/cyclohexanone mixture (from 66 to 85 %) in the oxidation of cyclohexane compared with Silicalite-1 and SBA-15 as supports.

Autothermal CaO Looping Biomass Gasification for Renewable Syngas Production.

Biomass gasification is regarded as a promising alternative to fossil fuels for producing sustainable and clean value-added products. However, the challenges including low energy efficiency, CO2 emission, and ash agglomeration significantly delay the deployment of the technology. Herein, we first proposed a novel autothermal CaO looping biomass gasification (Auto-CaL-Gas) technology, in which CaO-based materials react with flue gas with a high concentration of CO2 (>30 vol %) to produce heat inside the gasifier, simultaneously providing energy for low-temperature biomass gasification using CO2 as a gasification agent. Upon use of this concept the syngas production exhibited a significant increase from 0.21 kg/h to 0.90 kg/h in the Aspen simulation results and more than 3-fold improvement in the experimental results.

Lanthanide metal-organic frameworks as ratiometric fluorescent probes for real-time monitoring of PFOA photocatalytic degradation process.

The assessment of perfluorooctanoic acid (PFOA) photocatalytic degradation usually involves tedious pre-treatment and sophisticated instrumentation, making it impractical to evaluate the degradation process in real-time. Herein, we synthesized a series of lanthanide metal-organic frameworks (Ln-MOFs) with outstanding fluorescent sensing properties and applied them as luminescent probes in the photocatalytic degradation reaction of PFOA for real-time evaluation. As the catalytic reaction proceeds, the fluorescence color changes significantly from green to orange-red due to the different interaction mechanisms between the electron-deficient PFOA and smaller radius F- with the ratiometric fluorescent probe MOF-76 (Tb: Eu = 29:1). The limit of detection (LOD) was calculated to be 0.0127 mM for PFOA and 0.00746 mM for F-. In addition, the conversion rate of the catalytic reaction can be read directly based on the chromaticity value by establishing a three-dimensional relationship graph of G/R value-conversion rate-time (G/R indicates the ratio between green and red luminance values in the image.), allowing for real-time and rapid tracking of the PFOA degradation. The recoveries of PFOA and F- in the actual water samples were 99.3-102.7% (RSD = 2.2-4.4%) and 100.7-105.3% (RSD = 3.9-6.8%), respectively. Both theoretical calculations and experiments reveal that the detection mechanism was attributed to the photoinduced electron transfer and energy transfer between the analytes and the probe. This method simplifies the sample analysis process and avoids the use of bulky instruments, and thus has great potential on the design and development of quantitative time-resolved visualization methods to assess catalytic performance and reveal mechanisms.

Enhanced hydrogen production from catalytic biomass gasification with in-situ CO2 capture.

In order to cope with the global energy crisis and environmental pollution problems, there are urgent needs for clean energy such as biomass-derived hydrogen. CaO is effective to promote hydrogen production from biomass gasification due to its high capacity of in-situ CO2 capture. In this work, a two-stage fixed bed reactor was used to produce hydrogen by catalytic conversion of biomass with and without in-situ CO2 capture. In addition, three Ni loadings (5 wt%, 10 wt%, and 20 wt%) supported by Al2O3 and sol-gel CaO have been prepared and tested. The BET analysis shows the surface area of the catalysts increases first and then decreases with the increase of Ni loading. Results from high-resolution transmission electron microscopy (HRTEM) images reveals that NiO particles are well distributed over the porous CaO. The X-ray diffraction (XRD) analysis indicates the NiO nanocrystalline size is increased with increasing Ni loading on Ni/Al2O3, and the most homogeneous dispersion was shown by 10 wt% Ni/CaO. Around 666 mgCO2/gCaO of CO2 adsorption capacity and 850 min stability were obtained using the sol-gel CaO sorbent. Compared to the reference Ni/Al2O3 catalysts, the resistance of carbon deposition on the Ni/CaO results in a lower coke deposition, which is attributed to the basicity of the catalysts. In addition, the increase of loading promotes the decomposition of biomass-derived oxygenated compounds. Much more hydrogen is obtained using the Ni/CaO catalysts compared with Ni/Al2O3 due to in-situ CO2 capture. However, the sintering and particle agglomeration using the 20 wt% Ni-catalyst might be responsible for the reduction of hydrogen production. The highest H2 concentration of 19.32 vol% at 424 °C was obtained when the 10 wt% Ni/CaO catalyst was used.

Electrostatic Self-Assembly of Sandwich-Like CoAl-LDH/Polypyrrole/Graphene Nanocomposites with Enhanced Capacitive Performance.

A novel sandwich-like composite with ultrathin CoAl-layered double hydroxide (LDH) nanoplates electrostatically assembled on both sides of two-dimensional polypyrrole/graphene (PG) substrate has been successfully fabricated using facile hydrothermal techniques. The PG not only serves as an excellent conductive and structural scaffold to enhance the transmission of electrons and prevent aggregation of CoAl-LDH nanoplates but also contributes to the enhancement of the specific capacitance. Owing to the homogeneous dispersion of CoAl-LDH nanoplates and its intimate interaction with PG substrate, the resulting CoAl-LDH/PG nanocomposite material exhibits excellent capacitive performance, for example, enhanced gravimetric specific capacitance (864 F g-1 at 1 A g-1 ), high rate performance (75% retention at 20 A g-1), and excellent cycle life (almost no degradation in supercapacitor performance after 5000 cycles) in aqueous KOH solution. Furthermore, the assembled asymmetric capacitor is able to deliver a superhigh energy density of 46.8 Wh kg-1 at 1.2 kW kg-1 and maintain 90.1% of its initial capacitance after 10 000 cycles. These results indicate a rational assembly strategy toward a high-performance pseudocapacitive electrode material with excellent rate performance, high specific capacitance, and outstanding cycle stability.