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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. 

H₂S/CH₄and CO₂/CH₄separations show opposing trends, making simultaneous improvement challenging. This is addressed by increasing free volume to enhance competitive sorption effects and boosting diffusion selectivity throughin situcrosslinking.