Zeolites have exceptional catalytic performance in oil refining and chemical synthesis that can be attributed to their well-defined porous structures that host active sites. This study pinpoints the exact locations of aluminum atoms in ZSM-5 structures—a key zeolite catalyst. Aluminum siting governs catalytic efficiency in acid and redox processes. Anomalous x-ray powder diffraction (AXRPD) at the aluminum K-edge probes the long-range order of aluminum atoms within the ZSM-5 frameworks, precisely quantifying both isolated aluminum atoms and Al(-O-Si-O-)xAl sequences (aluminum pairs). Supported by nuclear magnetic resonance studies, AXRPD unambiguously determines the crystallographic organization of aluminum pairs, recognized spectroscopically as α, β, and γ sites, linking their distribution to superior catalytic activity in propene oligomerization. This combined approach provides essential insights for optimizing zeolite catalysts and enhancing their performance.
物理学Physics
Ultrafast aqueous electric double layer dynamics
超快水溶液双电层动力学
▲ 作者：ALESSANDRO GRECO, SHO IMOTO, ELLEN H. G. BACKUS, YUKI NAGATA, JOHANNES HUNGER AND MISCHA BONN
Chemical recycling to monomers is a key strategy for a sustainable circular polymer economy. However, most efforts have focused on polymers with carbon backbones. Recycling of silicone polymers and corresponding materials, featuring a robust inorganic backbone and tunable properties, remains in its infancy. We present a general method for depolymerization of a very wide range of silicone-based materials and postconsumer waste, including end-of-life cross-linked polydimethylsiloxane-based networks within formulated materials. The reaction proceeds at 40°C, harnessing an efficient gallium catalyst for a million-fold rate enhancement and boron trichloride as the chlorine source, to produce nearly quantitative yields of (methyl)chlorosilanes, key intermediates in the Müller-Rochow process that anchors the silicone industry.
Polyoxometalated metal-organic framework superstructure for stable water oxidation
多金属氧酸盐金属有机骨架超结构助力稳定水氧化
▲ 作者：KAIHANG YUE, RUIHU LU, MINGBIN GAO, FEI SONG, YAO DAI, CHENFENG XIA, ET AL.
Organic farming is often considered to be more sustainable than conventional farming. However, both farming systems comprise highly variable management practices. In this study, we show that in organic and conventional arable fields, the multifunctionality of soils decreases with increasing agricultural management intensity. Soil organic carbon content and bacterial biomass, respectively, were the strongest abiotic and biotic predictors of soil multifunctionality. Greater soil multifunctionality was associated with less-frequent inversion tillage and higher frequency of grass-legume cover cropping, and organic farming did not outperform conventional farming. Our results suggest that reducing management intensity will enhance soil multifunctionality in both conventional and organic farming. This implies that, in contexts where high-yielding, high-intensity agriculture prevails, the paradigm of sustainable intensification should be replaced by “productive deintensification.
Exoplanets classified as super-Earths are commonly observed on short-period orbits, close to their host stars, but their abundance on wider orbits is poorly constrained. Gravitational microlensing is sensitive to exoplanets on wide orbits. We observed the microlensing event OGLE-2016-BLG-0007, which indicates an exoplanet with a planet-to-star mass ratio roughly double the Earth-Sun mass ratio, on an orbit longer than Saturn’s. We combined this event with a larger sample from a microlensing survey to determine the distribution of mass ratios for planets on wide orbits. We infer that there are ~0.35 super-Earth planets per star on Jupiter-like orbits. The observations are most consistent with a bimodal distribution, with separate peaks for super-Earths and gas giants. We suggest that this reflects differences in their formation processes.
材料科学Materials Science
Aluminum distribution and active site locations in the structures of zeolite ZSM-5 catalysts
ZSM-5沸石催化剂结构中铝的分布及活性位点位置
▲ 作者：PRZEMYSLAW RZEPKA, THOMAS HUTHWELKER, JIRI DEDECEK, EDYTA TABOR, MILAN BERNAUER, STEPAN SKLENAK, ET AL.
The electric double layer (EDL) is critical in electrochemical capacitors and transistors, on-water chemistry, and bioelectric technologies. Ion dynamics within the EDL define the limits for charging and discharging processes. Classical EDL models struggle at high electrolyte concentrations, and observing EDL dynamics has been challenging. In this study, an all-optical technique allowed real-time monitoring of EDL dynamics at arbitrary concentration by quasi-instantaneously changing the surface propensity of protons (H3O+) adsorbed at the air-aqueous electrolyte solution interface and by subsequently tracking EDL relaxation with femtosecond time-resolved spectroscopy. EDL reorganization occurred on picosecond timescales and was strongly concentration dependent. Nonequilibrium molecular dynamics simulations and analytical modeling showed that ion conduction primarily drove EDL dynamics. This research quantified EDL dynamics and identified its primary driver, providing insights for optimization of electrochemical applications.
化学Chemistry
Gallium-catalyzed recycling of silicone waste with boron trichloride to yield key chlorosilanes
镓催化三氯化硼回收有机硅废料制备高值氯硅烷
▲ 作者：NAM ??C V?, AURéLIE BOULEGUE-MONDIèRE, NICOLAS DURAND , JOSéPHINE MUNSCH, MICKA?L BOSTE, RUDY LHERMET, ET AL.
Stable, nonprecious catalysts are vital for large-scale alkaline water electrolysis. Here, we report a grafted superstructure, MOF@POM, formed by self-assembling a metal-organic framework (MOF) with polyoxometalate (POM). In situ electrochemical transformation converts MOF into active metal (oxy)hydroxides to produce a catalyst with a low overpotential of 178 millivolts at 10 milliamperes per square centimeter in alkaline electrolyte. An anion exchange membrane water electrolyzer incorporating this catalyst achieves 3 amperes per square centimeter at 1.78 volts at 80°C and stable operation at 2 amperes per square centimeter for 5140 hours at room temperature. In situ electrochemical spectroscopy and theoretical studies reveal that the synergistic interactions between metal atoms create a fast electron-transfer channel from catalytic iron and cobalt sites, nickel, and tungsten in the polyoxometalate to the electrode, stabilizing the metal sites and preventing dissolution.
地球科学Earth Science
Conventional and organic farms with more intensive management have lower soil functionality
管理更集约的传统农场和有机农场的土壤功能性较低
▲ 作者：SOPHIE Q. VAN RIJSSEL, GUUSJE J. KOORNEEF, G. F. (CISKA) VEEN, MIRJAM M. PULLEMAN, RON G. M. DE GOEDE, ROB N. J. COMANS, ET AL.
