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Abstract Exceeding the energy density of lithium−carbon monofluoride (Li−CF_x), today's leading Li primary battery, requires an increase in fluorine content (x) that determines the theoretical capacity available from C−F bond reduction. However, high F‐content carbon materials face challenges such as poor electronic conductivity, low reduction potentials (<1.3 V versus Li/Li⁺), and/or low C−F bond utilization. This study investigates molecular structural design principles for a new class of high F‐content fluoroalkyl‐aromatic catholytes that address these challenges. A polarizable conjugated system—an aromatic ring with an alkene linker—functions as electron acceptor and redox initiator, enabling a cascade defluorination of an adjacent perfluoroalkyl chain (R_F= −C_nF_2n+1). The synthesized molecules successfully overcome premature deactivation observed in previously studied catholytes and achieve close‐to‐full defluorination (up to 15/17 available F), yielding high gravimetric capacities of 748 mAh g⁻¹_{fluoroalkyl‐aromatic}and energies of 1785 Wh kg⁻¹_{fluoroalkyl‐aromatic}. The voltage compatibility between fluoroalkyl‐aromatics and CF_xenables design of hybrid cells containing C−F redox activity in both solid and liquid phases, with a projected enhancement of Li–CF_xgravimetric energy by 35% based on weight of electrodes+electrolyte. With further improvement of cathode architecture, these “liquid CF_x” analogues are strong candidates for exceeding the energy limitations of today's primary chemistries. 

Abstract The detection of methane is important for industry, environment, and our daily life, but is made challenging by its small size, high volatility, and nonpolar nature. Herein, a tungsten‐capped calix[4]arene‐basedp‐doped conducting polymer with hexafluorophosphate or perchlorate counter‐anions as a transducer is used to detect methane in dry air. The host–guest interaction between calixarene moieties within the polymer chain and methane molecules leads to the resistance variation of the polymer. The experimental limit of detection (LoD) of methane for the polymer‐based sensor is demonstrated to be less than 50 ppm at room temperature, and the extrapolated theoretical LoD of 2 ppm represents exceptional sensitivity to methane. Furthermore, the discrimination of methane from interfering volatile organic compounds is achieved by exploiting a sensor array using complementary chemiresistors and principal component analysis. 

Abstract Fluid‐like sliding graphenes but with solid‐like out‐of‐plane compressive rigidity offer unique opportunities for achieving unusual physical and chemical properties for next‐generation interfacial technologies. Of particular interest in the present study are graphenes with specific chemical functionalization that can predictably promote adhesion and wetting to substrate and ultralow frictional sliding structures. Lubricity between stainless steel (SS) and diamond‐like carbon (DLC) is experimentally demonstrated with densely functionalized graphenes displaying dynamic intersheet bonds that mechanically transform into stable tribolayers. The macroscopic lubricity evolves through the formation of a thin film of an interconnected graphene matrix that provides a coefficient of friction (COF) of 0.01. Mechanical sliding generates complex folded graphene structures wherein equilibrated covalent chemical linkages impart rigidity and stability to the films examined in macroscopic friction tests. This new approach to frictional reduction has broad implications for manufacturing, transportation, and aerospace. 

Abstract Polymer membranes with ultrahigh CO₂permeabilities and high selectivities are needed to address some of the critical separation challenges related to energy and the environment, especially in natural gas purification and postcombustion carbon capture. However, very few solution‐processable, linear polymers are known today that access these types of characteristics, and all of the known structures achieve their separation performance through the design of rigid backbone chemistries that concomitantly increase chain stiffness and interchain spacing, thereby resulting in ultramicroporosity in solid‐state chain‐entangled films. Herein, the separation performance of a porous polymer obtained via ring‐opening metathesis polymerization is reported, which possesses a flexible backbone with rigid, fluorinated side chains. This polymer exhibits ultrahigh CO₂permeability (>21 000 Barrer) and exceptional plasticization resistance (CO₂plasticization pressure > 51 bar). Compared to traditional polymers of intrinsic microporosity, the rate of physical aging is slower, especially for gases with small effective diameters (i.e., He, H₂, and O₂). This structural design strategy, coupled with studies on fluorination, demonstrates a generalizable approach to create new polymers with flexible backbones and pore‐forming side chains that have unexplored promise for small‐molecule separations.