查看更多>>摘要：We have constructed a state-of-the-art polyimidazole-supported trimetallic composite, PIm/Fe^Zn^Ag, for organic synthesis, transformation, and environmental remediation on a single platform. The sustainable chemistry of organic reactions involving three-component coupling, CO2 insertion, [3 + 2]-click, Knoevenagel condensation, and CO2 cycloaddition reactions, and environmental pollutant reduction and bacterial inhibition are performed to comprehensively evaluate the power of this multifunctional catalyst. Most reactions withstand good functional group tolerance, producing forty-one derivatives with molecularly distinct moieties at good to near-quantitative yields under benign reaction conditions. Full chemical, microscopic, and structural characterizations reveal that metallic Ag, ZnO, and Fe2O3 with well-defined nanostructures are well interspersed and integrated on the PIm support. The metallic centers provide a conjugated multivalent architecture that work synergistically on a platform with moderate surface area and good CO2 adsorption capacity is the key to the multi-functionalities and effectiveness of PIm/Fe^Zn^Ag, which is a current demand for developing green sustainable heterogeneous catalysts.
查看更多>>摘要：Covalent organic framework (COF) is a novel platform to develop efficient and green safe heterogeneous photocatalysts. Additionally, multiple photoredox reactions and mechanism studies over porous catalysts remain to be further exploited. In this context, two benzofuran-embedded COFs (BF-COFs) with favorable solvent tolerance were constructed via tautomerism strategy. Attributing to the benzofuran-hetero[6]radialene knots, BF-COFs displayed as donor-acceptor properties, and exhibited wide visible light response range and well separation efficiency for photogenerated charges. Under visible-light, BF-COFs could promote the C-S bond formation reaction between β-ketoate ester and its analogues with NH4SCN, affording multi-substituted olefins (28 examples, upto 98% yield) efficiently. Moreover, the atomic economic strategy was also applicative to prepare L-proline derived olefins (≥ 99% ee), which could be further converted into the chiral amino-substituted thiazoles (99% yield and ≥ 99% ee). The research about BF-COFs sheds light on the green construction of C-S bond, (chiral) olefins and chiral amino thiazoles.
查看更多>>摘要：Recently, catalyst-free activation of peroxydisulfate (PDS) via visible light has been extensively investigated. However, the intrinsic relationship between the activation of PDS and the characteristics of pollutants has been largely ignored. This study reports that PDS activation by visible light without any artificial catalyst for the removal of fluoroquinolones (FQs), which reduced the adverse on ecological environment and human health concerns. Importantly, the mechanism of PDS activation by the excited triplet state of FQs (~3FQs~*) was proposed. Experimental results demonstrated PDS could generate more -OH with the existence of ~3FQs~*. Meanwhile, the electron transfer pathways from FQs or ~3FQs~* to PDS were studied. Both radical and non-radical oxidation reactions lead to the degradation of FQs in the Vis/PDS system. The degradation pathways and reactive sites were clarified by QTOF analysis and DFT calculations. Additionally, the degradation experiments of various contaminants demonstrated that the system showed excellent selective oxidation for FQs.
查看更多>>摘要：Designing Fe-carbon catalyst with multiple active sites for persulfate (PS) activation to water purification is challenging. Herein, nitrogen-doped biochar (NBC) loaded with ferrous sulfide (FeS) was synthesized via two-step ball milling. In FeS@NBC_(BM)/PS system, both electron transfer process and reactive oxygen species (ROSs) including SO_4~(·-), ~·OH, O_2~(·-) and ~1O2 contributed to phenol degradation. Surface-bound S(II) not only interacted with PS for generating SO_4~(·-), but also accelerated Fe(III)/Fe(II) circulation by reducing Fe(III). NBC was favorable for phenol adsorption and exposure of oxygen-containing groups, graphitic and pyridinic N active sites, which mediated electron transfer or ROSs formation. Owing to multiple active sites, this system fast achieved almost complete phenol degradation with excellent adaptability to wide pH range of 3-9, high anti-interference capacity to coexisting substances, and was efficient to various water matrices. Furthermore, phenol degradation pathways were elucidated by DFT calculations with intermediate products showing lower toxicity, demonstrating great potentials of proposed system.
查看更多>>摘要：Direct catalytic hydrogenation of CO2 is a highly promising route for olefin synthesis. However, achieving high olefin selectivity is predicated on the development of a selective catalyst with acceptable yield and stability. Herein, we report a Sr and Na co-decorated Fe catalyst that showed stable performance in the synthesis of high-valued olefins (ethene, propene and linear α-olefins) with space-time yield up to 290 mg g_(cat)~(-1)h~(-1) without significant deactivation for over 500 h on-stream. The excellent catalytic performance is attributed to the cooperative effect of Sr and Na on the distinct sites (Fe5C2, Fe3C, Fe3O4) in catalyst. In particular, SrCO3 promoted the dispersion of binding Fe sites that facilitated the formation and stabilization of FeC_x phase. Simultaneously, Sr contributed to the electron interaction between Na and Fe species. The dual effect of Sr as both structural and electronic promoters coordinatively improved C-O dissociative adsorption and subsequent C-C coupling, thus facilitated CO2 hydrogenation.
查看更多>>摘要：Water, which is the host of life, introduces many unusual features into the kinetics and energetics of biological reaction systems catalyzed by enzymes. Single atom catalyst has great potential to mimic biological enzymes in regard to special catalytic sites and high efficiency. Here we report a significant promotion by H2O in the environmental reduction of nitrobenzene on an environmentally friendly humic acid supported Pt single atom catalyst. No nitrobenzene conversion took place when only organic solvents were used while high activity of the catalyst was observed in aqueous mixtures (turnover frequency is as high as 1883 h~(-1)). Experiments and density functional theory calculation show that H2O greatly decreased the energy barrier by enabling a biomimetic electron-proton transfer for the hydrogenation process even on single atom Pt catalyst, and a new reaction pathway with phenyl-λ~1-azane as intermediate in the direct hydrogenation of nitrobenzene is proposed.
查看更多>>摘要：Sorption-enhanced steam reforming of ethanol shows potential of supplying high-quality hydrogen with in situ CO2 capture, but suffers from sorbent deactivation. This paper describers the design of functionalized xNiO/CagCo_(12)O_(28) materials, whose phases can be segregated once triggered by the lattice oxygen consumption via NiO/Ca9Co_(12)O_(28)-O~(2-)→Ni-Co+CaO, thus acting as the catalytic sorbent. Their superiorities are demonstrated in: (i) low-temperature activation via lattice oxygen induction; (ii) recyclability via lattice oxygen replenishment; hi) high-quality hydrogen actuation via in situ CO2 adsorption. Hydrogen concentration of 95.56 vol% and near-complete ethanol conversion can be achieved. Moreover, stability across 50 repeated cycles without obvious reduction in catalytic reforming and CO2 adsorption is demonstrated. In situ XKD studies demonstrate the formation of the Ni-Co alloy and the reorganization of the catalytic sorbent. The adsorption energies of ethanol on the surface of Ni(III), Co(III), and Ni-Co(III) were studied by DFT calculations, reaffirming the higher catalytic activity of Ni-Co alloys.
查看更多>>摘要：Artificial photosynthesis is a promising strategy for converting CO2 and H2O into fuels and value-added products, while the low catalytic efficiency greatly restricts its practical applications. Herein, we demonstrated that graphitic carbon nitride with spatially confined Fe single-atom and potassium ion (FeN4/K-g-C3N4) exhibited the high activity and selectivity for photocatalytic CO2 reduction. Specifically, the conversion rates of CO2 into CO could achieve up to 20.00 μmol g~(-1) h~(-1) with nearly 100% selectivity, more than 10 times higher performances than pristine g-C3N4. Comprehensive characterizations and theoretical calculations revealed that the single-atom Fe bonded with four N atoms in g-C3N4 intralayer, which serve as the active center for absorption and activation of CO2 molecules. The alkali K ions inserted the g-C3N4 interlayers owing to their suitable diameters, which could effectively promote charge separation and transfer. Synergizing the spatial confinements of Fe single-atoms and K ions in g-C3N4 remarkably promoted the photocatalytic activity and selectivity for CO2 reduction into CO.
查看更多>>摘要：Liquid fuel reforming is an efficient way to produce hydrogen for mobile fuel cell systems. However, the catalyst is easily damaged by coke formation and thermal sintering during the reaction. In this study, an exsolved PtRu alloy catalyst was investigated for hydrogen production via diesel reforming. The crystal structure, electronic state, and surface morphology of the catalyst were analyzed by XRD, XPS, and TEM. The energetics for the exsolution of metals and their surface alloy formation were also predicted based on DFT calculations. The as-prepared catalyst was found to be a solid solution where Pt and Ru were incorporated into a CeO2 lattice. During the reaction, Pt and Ru were exsolved from the support to form PtRu alloy nanoparticles. Synergistic effects were observed in the PtRu alloy catalyst. It showed improved activity and stability with high resistance to coke formation and thermal sintering compared to monometallic Pt and Ru catalysts.
查看更多>>摘要：Downsizing supported metal of Fe~0-based materials in dealing with ever-growing pharmaceutical contamination issues are highly desired but still challenging. Herein, we develop a modular design protocol to synthesize a family of ultrafine alloy nanoclusters embedded in a nitrogen-enriched carbon framework (NEC@FeM (M=Pd, Pt, Au)). Engineering the fine structure of nitrogen-enriched carbon and interfacial interaction with bimetallic nanoclusters largely suppresses bimetallic overgrowth, eventually producing supported ultrafine (< 4 nm), highly dispersed, well-alloyed nanoclusters. The alloying Fe~0 with M for ultrafine nanoclusters optimize the electron flow, chemical stability, and catalytic property, resulting in the obtained NEC@FeM exhibiting excellent doxorubicin (DOX) degradation performance. Density functional theory calculation combined with experimental results attribute the outstanding DOX degradation ability of NEC@FePd originally to the synergistic effect of enhanced DOX affinity and efficient electrons transfer from Fe to DOX. This work provides a paradigm for the design of ultrafine Fe~0-based nanocluster with application in pollution control.
NSTL