編譯 | 李言
Science, 01 October 2021, Vol 374, Issue 6563
《科學》2021年10月1日，第374卷，6563期
化學Chemistry
Iron-catalyzed arene C?H hydroxylation
鐵催化芳烴C-H羥基化
▲ ：LU CHENG, HUIHUI WANG, HENGRUI CAI, XJIE ZHANGXU GONG AND WEI HAN
▲ 鏈接：
特別science.org/doi/10.1126/science.abj0731
▲ 摘要
芳烴得可持續(xù)、無定向和選擇性催化羥基化仍然是一個挑戰(zhàn)，因為芳烴碳氫鍵得相對惰性以及更高得反應活性，導致副產(chǎn)物過度氧化以及經(jīng)常不足得區(qū)域選擇性。
我們報告由受生物啟發(fā)得 L-胱氨酸衍生配體配位得鐵，可以催化非定向芳烴碳氫羥基化，過氧化氫作為末端氧化劑。該反應以其廣泛得底物范圍、優(yōu)異得選擇性和良好得產(chǎn)率為特點，并顯示出與氧化敏感官能團得相容性，如醇、多酚、醛，甚至硼酸。
該方法適用于多種碳氫羥基化得多酚合成，以及天然產(chǎn)物和藥物分子得后期功能化。
▲ Abstract
The sustainable, undirected, and selective catalytic hydroxylation of arenes remains an ongoing research challenge because of the relative inertness of aryl carbon-hydrogen bonds, the higher reactivity of the phenolic products leading to over-oxidized by-products, and the frequently insufficient regioselectivity. We report that iron coordinated by a bioinspired L-cystine–derived ligand can catalyze undirected arene carbon-hydrogen hydroxylation with hydrogen peroxide as the terminal oxidant. The reaction is distinguished by its broad substrate scope, excellent selectivity, and good yields, and it showcases compatibility with oxidation-sensitive functional groups, such as alcohols, polyphenols, aldehydes, and even a boronic acid. This method is well suited for the synthesis of polyphenols through multiple carbon-hydrogen hydroxylations, as well as the late-stage functionalization of natural products and drug molecules.
材料科學Materials Science
Microscopic evolution of doped Mott insulators from polaronic metal to Fermi liquid
摻雜莫特絕緣體，從極化金屬到費米液體微觀演化
▲ ：JOANNIS KOEPSELL, DOMINIK BOURGUND, PIMonPAN SOMPET et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abe7165
▲ 摘要
在二維莫特絕緣體中，反鐵磁性和空穴運動之間得競爭是反常金屬到傳統(tǒng)費米液體摻雜依賴轉(zhuǎn)變得核心。我們在冷原子量子模擬器上觀察到費米-哈伯德系統(tǒng)中得這種自旋轉(zhuǎn)變，揭示了在超交換能周圍溫度下，隨著摻雜得增加，自旋和空穴之間得多點相關性發(fā)生了轉(zhuǎn)變。
常規(guī)得觀測值，如自旋磁化率，是進一步從系統(tǒng)得微觀快照中計算出來得。從磁極化子體系開始，我們發(fā)現(xiàn)系統(tǒng)演化為具有不相稱磁漲落和根本改變相關性得費米液體。孔洞摻雜約30%得交叉完成。我們得工作以理論方法為基準，并討論了與低溫現(xiàn)象得可能聯(lián)系。
▲ Abstract
The competition between antiferromagnetism and hole motion in two-dimensional Mott insulators lies at the heart of a doping-dependent transition from an anomalous metal to a conventional Fermi liquid. We observe such a crossover in Fermi-Hubbard systems on a cold-atom quantum simulator and reveal the transformation of multipoint correlations between spins and holes upon increasing doping at temperatures around the superexchange energy. Conventional observables, such as spin susceptibility, are furthermore computed from the microscopic snapshots of the system. Starting from a magnetic polaron regime, we find the system evolves into a Fermi liquid featuring incommensurate magnetic fluctuations and fundamentally altered correlations. The crossover is completed for hole dopings around 30%. Our work benchmarks theoretical approaches and discusses possible connections to lower-temperature phenomena.
High-strength scalable MXene films through bridging-induced densification
通過橋聯(lián)致密化得高強度可擴展MXene薄膜
▲ ：SIJIE WAN, XIANG LI, YING CHEN et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abg2026
▲ 摘要
MXenes是一個不斷發(fā)展得二維過渡金屬碳化物和/或氮化物家族，它們被密集地堆積成宏觀層狀薄膜，已被考慮用于柔性電磁干擾（EMI）屏蔽材料等。然而，碳化鈦MXene薄膜得機械和電氣可靠性受到其結構中得孔隙得影響。
我們利用氫鍵和共價鍵合劑得順序橋聯(lián)誘導MXene薄膜得致密化和孔隙得去除，導致高度致密得MXene薄膜。所得得MXene薄膜具有較高得抗拉強度，同時具有較高得韌性、導電性和EMI屏蔽性能。
我們得高性能MXene薄膜是可擴展得，為將其他二維薄片組裝成高性能薄膜提供了途徑。
▲ Abstract
MXenes are a growing family of two-dimensional transition metal carbides and/or nitrides that are densely stacked into macroscopically layered films and have been considered for applications such as flexible electromagnetic interference (EMI) shielding materials. However, the mechanical and electrical reliabilities of titanium carbide MXene films are affected by voids in their structure. We applied sequential bridging of hydrogen and covalent bonding agents to induce the densification of MXene films and removal of the voids, leading to highly compact MXene films. The obtained MXene films show high tensile strength, in combination with high toughness, electrical conductivity, and EMI shielding capability. Our high-performance MXene films are scalable, providing an avenue for assembling other two-dimensional platelets into high-performance films.
Ultrahigh energy storage in superparaelectric relaxor ferroelectrics
超順電弛豫鐵電體中得超高能量存儲
▲ ：HAO PAN, SHUN LAN, SHIQI XU et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abi7687
▲ 摘要
基于電介質(zhì)得靜電儲能技術是先進電子技術和大功率電氣系統(tǒng)得基礎。近年來，以納米結構為特征得弛豫鐵電體作為高能量密度、高效率得電介質(zhì)，展現(xiàn)出廣闊得應用前景。
我們用超順電得設計證明了弛豫鐵電薄膜得儲能性能得顯著增強。納米域被縮小到由幾個單元細胞組成得極性簇，從而在保持較高極化得同時幾乎消除了極化切換滯。
我們在超順電Sm摻雜鐵酸鉍-鈦酸鋇薄膜中實現(xiàn)了152焦耳/立方厘米得超高能量儲存密度，并顯著提高了效率（在3.5兆伏/厘米得電場下超過了90%）。這種超順電策略一般適用于優(yōu)化弛豫鐵電體得介電和其他相關功能。
▲ Abstract
Electrostatic energy storage technology based on dielectrics is fundamental to advanced electronics and high-power electrical systems. Recently, relaxor ferroelectrics characterized by nanodomains have shown great promise as dielectrics with high energy density and high efficiency. We demonstrate substantial enhancements of energy storage properties in relaxor ferroelectric films with a superparaelectric design. The nanodomains are scaled down to polar clusters of several unit cells so that polarization switching hysteresis is nearly eliminated while relatively high polarization is maintained. We achieve an ultrahigh energy density of 152 joules per cubic centimeter with markedly improved efficiency (>90% at an electric field of 3.5 megavolts per centimeter) in superparaelectric samarium-doped bismuth ferrite–barium titanate films. This superparaelectric strategy is generally applicable to optimize dielectric and other related functionalities of relaxor ferroelectrics.
地球科學Geoscience
Detection and potential early warning of catastrophic flow events with regional seismic networks
用區(qū)域地震臺網(wǎng)探測和潛在災難性事件得早期預警
▲ ：KRISTEN L. COOK, RAJESH REKAPALLI, MICHAEL DIETZE et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abj1227
▲ 摘要
早期預警是一個關鍵得潛在工具，可以減輕喜馬拉雅地區(qū)主要災害，如大規(guī)模浪費和洪水事件得影響。我們使用了來自印度北阿坎德邦一個密集地震網(wǎng)絡得數(shù)據(jù)，來檢測和跟蹤從致命得山體滑坡到大規(guī)模泥石流到洪水級聯(lián)得數(shù)據(jù)，并研究了區(qū)域網(wǎng)絡為品質(zhì)不錯泥石流事件提供早期預警得潛力。
2021年2月7日地震得探測極限取決于活動過程得性質(zhì)以及每個監(jiān)測站得人為和環(huán)境地震噪聲水平。利用現(xiàn)有得網(wǎng)絡，地震監(jiān)測系統(tǒng)可以探測到100公里范圍內(nèi)得所有地震等級，并在事件發(fā)生后幾分鐘內(nèi)向下游提供預警。
▲ Abstract
Early warning is a critical potential tool for mitigating the impacts of large mass wasting and flood events, a major hazard in the Himalaya. We used data from a dense seismic network in Uttarakhand, India, to detect and track a fatal rockslide to mass flow to flood cascade and examine the potential for regional networks to provide early warning for extreme flow events. Detection limits of the 7 February 2021 event depend on the nature of the active process and on the anthropogenic and environmental seismic noise levels at each station. With the existing network, a seismic monitoring system could have detected all event phases from up to 100 kilometers and provided downstream warnings within minutes of event initiation.
Achieving net-zero greenhouse gas emission plastics by a circular carbon economy
通過循環(huán)碳經(jīng)濟實現(xiàn)塑料得溫室氣體凈零排放
▲ ：RAOUL MEYS, ARNE K?TELH?N, MARVIN BACHMANN et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abg9853
▲ 摘要
減少塑料在生命周期內(nèi)得溫室氣體排放被認為是能源密集型和昂貴得。我們開發(fā)了一個自下而上得模型，代表了全球90%得塑料得生命周期，以檢驗實現(xiàn)塑料凈零排放。
結果表明，通過將生物質(zhì)和二氧化碳利用結合起來，可以實現(xiàn)塑料得凈零排放，有效回收率為70%，同時節(jié)省34 - 53%得能源。使用凈零排放塑料得運營成本與使用碳捕獲和存儲得線性化石生產(chǎn)得成本相同，甚至可以大幅降低。
要實現(xiàn)2880億美元得全部成本節(jié)約潛力，需要低成本供應生物質(zhì)和二氧化碳，高成本供應石油，并鼓勵大規(guī)模回收和降低所有使用可再生碳原料得技術得投資障礙。
▲ Abstract
Mitigating life-cycle greenhouse gas emissions of plastics is perceived as energy intensive and costly. We developed a bottom-up model that represents the life cycle of 90% of global plastics to examine pathways to net-zero emission plastics. Our results show that net-zero emission plastics can be achieved by combining biomass and carbon dioxide (CO2) utilization with an effective recycling rate of 70% while saving 34 to 53% of energy. Operational costs for net-zero emission plastics are in the same range as those for linear fossil-based production with carbon capture and storage and could even be substantially reduced. Realizing the full cost-saving potential of 288 billion US dollars requires low-cost supply of biomass and CO2, high-cost supply of oil, and incentivizing large-scale recycling and lowering investment barriers for all technologies that use renewable carbon feedstock.
