11 Search Results

The use of covalent organic frameworks (COFs) for hazardous radioiodine capture has been highly sought after recently. However, the synthesis of high-performance COF adsorbents while circumventing the limitations of traditional solvothermal methods remains largely unexplored. Herein, we for the first time combine microwave-assisted synthesis and mixed-linker strategy to fabricate multivariate COF adsorbents (X% OMe-TFB-BD COFs, X% = 0, 33, 50, 67, and 100 mol%) with varying ratios of benzidine (BD) and 3,3'-dimethoxylbenzidine (BD-OMe) linkers in a rapid and facile manner. Adjusting the BD-OMe/BD mole ratios has led to distinct variations in density, crystallinity, porosity, morphology, and thermal/chemical stability of themore » resultant COFs, which empowered fine-tuning of the adsorption performance towards static iodine vapor. Remarkably, the 50% OMe-TFB-BD COF exhibited an ultrahigh iodine adsorption capability of 8.2 g g^–1, surpassing those of single-component COFs, mixed-linker COFs with other methoxy content, physically blended mixtures, and most existing COF adsorbents. Moreover, 50% OMe-TFB-BD COF was recyclable seven times without obvious loss in its adsorption capacity. Finally, this work underscores the substantial potential of microwave-assisted mixed-linker strategy as a viable approach for developing multivariate COFs with shortened reaction times, precisely tailored pore environment, and tunable sorption properties, which are of considerable promise for environmental remediation and other niche applications.« less

Reversibly adjusting the active structures of supported metal catalysts in response to dynamic working conditions has long been pursued. Here we report the reaction-environment-modulated transformations of subnanometre-sized Pd on CeO₂ for efficient methane removal, leveraging the reaction environments at different stages of automotive exhaust aftertreatment. During the cold start of vehicles, inactive Pd₁ single atoms are readily transformed into PdO_$$x$$ subnanometre clusters by CO even at room temperature with excess O₂, resulting in boosted low-temperature CH₄ oxidation. At elevated temperatures, dispersion of PdO_$$x$$ cluster into Pd₁ against metal sintering renders outstanding hydrothermal stability to the catalyst, to be activated duringmore » the next vehicle start. Combined experimental and computational studies elucidate the dynamically evolved Pd speciation on CeO₂ at an atomic level. In conclusion, modulating the reversible nature of supported metals helps overcome the long-existing trade-off between low-temperature activity and high-temperature stability, also providing a new paradigm for designing intelligent catalysts that brings single-atom/cluster catalysts closer to real applications.« less

In this study, liquid-phase chemical grafting method was used to graft Zn onto TiO₂ with preferentially exposed (1 0 1) or (0 0 1) facet. The obtained Zn_xTi_yO_z materials were characterized using various techniques (e.g., XRD, Raman, DRIFTS etc.) and evaluated for the acetone-to-isobutene reaction. It was found that over TiO₂ (0 0 1), both terminal and bridging hydroxyls were readily titrated by Zn deposition, whereas a substantial amount of bridging hydroxyls on TiO₂ (1 0 1) remained. Although dominant Zn-O-terminated surface was obtained on two Zn_xTi_yO_z samples, bridging hydroxyls with high H-D exchange reactivity were observed on Zn_xTi_yO_z (1more » 0 1) compared with Zn_xTi_yO_z (0 0 1). The bridging hydroxyls showing rapid proton transfer efficiently stabilizes a transition state of diacetone alcohol intramolecular rearrangement for isobutene production as opposed to the diacetone alcohol dehydration.« less

Cu sulfides as a template for Ag/Cu sulfide catalysts for electrochemical CO ₂ . With the introduction of Ag, nanosheet show increased C2+ product generation. The catalysts undergo a morphology evolution as CO ₂ reduction proceeds.

Abstract Efficient electro‐oxidation of formic acid, methanol, and ethanol is challenging owing to the multiple chemical reaction steps required to accomplish full oxidation to CO ₂ . Herein, a ternary CoPtAu nanoparticle catalyst system is reported in which Co and Pt form an intermetallic L1 ₀ ‐structure and Au segregates on the surface to alloy with Pt. The L1 ₀ ‐structure stabilizes Co and significantly enhances the catalysis of the PtAu surface towards electro‐oxidation of ethanol, methanol, and formic acid, with mass activities of 1.55 A/mg _Pt , 1.49 A/mg _Pt , and 11.97 A/mg _Pt , respectively in 0.1  m HClO ₄more » . The L1 ₀ ‐CoPtAu catalyst is also stable, with negligible degradation in mass activities and no obvious Co/Pt/Au composition changes after 10 000 potential cycles. The in situ surface‐enhanced infrared absorption spectroscopy study indicates that the ternary catalyst activates the C−C bond more efficiently for ethanol oxidation.« less

Abstract Efficient electro‐oxidation of formic acid, methanol, and ethanol is challenging owing to the multiple chemical reaction steps required to accomplish full oxidation to CO ₂ . Herein, a ternary CoPtAu nanoparticle catalyst system is reported in which Co and Pt form an intermetallic L1 ₀ ‐structure and Au segregates on the surface to alloy with Pt. The L1 ₀ ‐structure stabilizes Co and significantly enhances the catalysis of the PtAu surface towards electro‐oxidation of ethanol, methanol, and formic acid, with mass activities of 1.55 A/mg _Pt , 1.49 A/mg _Pt , and 11.97 A/mg _Pt , respectively in 0.1  m HClO ₄more » . The L1 ₀ ‐CoPtAu catalyst is also stable, with negligible degradation in mass activities and no obvious Co/Pt/Au composition changes after 10 000 potential cycles. The in situ surface‐enhanced infrared absorption spectroscopy study indicates that the ternary catalyst activates the C−C bond more efficiently for ethanol oxidation.« less

Monodisperse nanoparticles are successful model systems for understanding structure–property relationships at the nanoscale and applications like catalysis and nanomedicine.

Abstract We report a general chemical approach to synthesize strongly ferromagnetic rare‐earth metal (REM) based SmCo and SmFeN nanoparticles (NPs) with ultra‐large coercivity. The synthesis started with the preparation of hexagonal CoO+Sm ₂ O ₃ (denoted as SmCo‐O) multipods via decomposition of Sm(acac) ₃ and Co(acac) ₃ in oleylamine. These multipods were further reduced with Ca at 850 °C to form SmCo ₅ NPs with sizes tunable from 50 to 200 nm. The 200 nm SmCo ₅ NPs were dispersed in ethanol, and magnetically aligned in polyethylene glycol (PEG) matrix, yielding a PEG‐SmCo ₅ NP composite with the room temperature coercivity ( Hmore » _c ) of 49.2 kOe, the largest H _c among all ferromagnetic NPs ever reported, and saturated magnetic moment ( M _s ) of 88.7 emu g ⁻¹ , the highest value reported for SmCo ₅ NPs. The method was extended to synthesize other ferromagnetic NPs of Sm ₂ Co ₁₇ , and, for the first time, of Sm ₂ Fe ₁₇ N ₃ NPs with H _c over 15 kOe and M _s reaching 127.9 emu g ⁻¹ . These REM based NPs are important magnetic building blocks for fabrication of high‐performance permanent magnets, flexible magnets, and printable magnetic inks for energy and sensing applications.« less

We report here a general chemical approach to synthesize strongly ferromagnetic rare-earth metal (REM) based SmCo and SmFeN nanoparticles (NPs) with ultra-large coercivity. The synthesis started with the preparation of hexagonal CoO+Sm₂O₃ (denoted as SmCo-O) multipods via decomposition of Sm(acac)₃ and Co(acac)₃ in oleylamine. These multipods were further reduced with Ca at 850 °C to form SmCo₅ NPs with sizes tunable from 50 to 200 nm. The 200 nm SmCo₅ NPs were dispersed in ethanol, and magnetically aligned in polyethylene glycol (PEG) matrix, yielding a PEG-SmCo₅ NP composite with the room temperature coercivity (H_c) of 49.2 kOe, the largest H_cmore » among all ferromagnetic NPs ever reported, and saturated magnetic moment (M_s) of 88.7 emu g^-1, the highest value reported for SmCo₅ NPs. The method was extended to synthesize other ferromagnetic NPs of Sm₂Co₁₇, and, for the first time, of Sm₂Fe₁₇N₃ NPs with H_c over 15 kOe and M_s reaching 127.9 emu g^-1. These REM based NPs are important magnetic building blocks for fabrication of high-performance permanent magnets, flexible magnets, and printable magnetic inks for energy and sensing applications.« less