Electrochemical reduction of CO2 to valuable fuels is appealing for CO2 fixation and energy storage. However, the development of electrocatalysts with high activity and selectivity in a wide potential window is challenging. Herein, atomically thin bismuthene (Bi‐ene) is pioneeringly obtained by an in situ electrochemical transformation from ultrathin bismuth‐based metal–organic layers. The few‐layer Bi‐ene, which possesses a great mass of exposed active sites with high intrinsic activity, has a high selectivity (ca. 100 %), large partial current density, and quite good stability in a potential window exceeding 0.35 V toward formate production. It even deliver current densities that exceed 300.0 mA cm−2 without compromising selectivity in a flow‐cell reactor. Using in situ ATR‐IR spectra and DFT analysis, a reaction mechanism involving HCO3− for formate generation was unveiled, which brings new fundamental understanding of CO2 reduction.

The detection of hypochlorite (ClO–) content in tap water is extremely important because excess amounts of hypochlorite can convert into highly toxic species and inadequate amounts of hypochlorite cannot fully kill bacteria and viruses. Although several metal–organic frameworks (MOFs) have been successfully employed as fluorescent sensors for hypochlorite detection, all these sensors are based on single emission that responds to the dose of hypochlorite. Ratiometric sensors are highly desirable, which can improve the sensitivity, accuracy, and reliability via self-calibration. Herein, a nanoscale dual-emission multivariate 5-5-Eu/BPyDC@MOF-253-NH2 was synthesized by sequential mixed-ligand self-assembly and postsynthesis method. Among the two emission bands of 5-5-Eu/BPyDC@MOF-253-NH2, the strong blue emitting derived from ligands is sensitive to hypochlorite, while the red emitting derived from Eu­(III) almost keeps invariable. Therefore, 5-5-Eu/BPyDC@MOF-253-NH2 was exploited as a fluorescent ratiometric nanosensor for “on–off” sensing of hypochlorite. Notably, the proposed sensing system showed an excellent performance including fast response (within 15 s), relative high specificity, wide linear range (0.1–30 μM), and low detection limit (0.094 μM). Besides, the suppressed blue emitting was recovered after the addition of ascorbic acid (AA) that consumes ClO– via the redox reaction. Therefore, 5-5-Eu/BPyDC@MOF-253-NH2 was further employed as a fluorescent ratiometric nanosensor for the “on–off–on” sensing of AA. This work represents the first MOF-based fluorescent “switch” for the ratiometric sensing of hypochlorite and the second for ratiometric sensing of AA.

Electrochemical reduction of CO2 to valuable fuels is appealing for CO2 fixation and energy storage. However, the development of electrocatalysts with high activity and selectivity in a wide potential window is challenging. Herein, atomically thin bismuthene (Bi‐ene) is pioneeringly obtained by an in situ electrochemical transformation from ultrathin bismuth‐based metal–organic layers. The few‐layer Bi‐ene, which possesses a great mass of exposed active sites with high intrinsic activity, has a high selectivity (ca. 100 %), large partial current density, and quite good stability in a potential window exceeding 0.35 V toward formate production. It even deliver current densities that exceed 300.0 mA cm−2 without compromising selectivity in a flow‐cell reactor. Using in situ ATR‐IR spectra and DFT analysis, a reaction mechanism involving HCO3− for formate generation was unveiled, which brings new fundamental understanding of CO2 reduction.

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First-principles calculations were used to assess the potential of ordered TiMC and TiMCT2 (M = Cr, Mo; T = O, S) monolayers as high-performance anode materials of lithium-ion batteries (LIBs). The predicted results reveal that Li can easily adsorb on the surfaces of TiMC monolayers, especially on the TiMCT2 monolayers. The density of states analysis shows that TiMC (M = Cr and Mo) and TiCrCO2 monolayers exhibit metallicity with good intrinsic advantages for the application of LIBs. The calculated lowest Li-ion diffusion barriers of pristine TiCrC and TiMoC monolayers on the Ti surface are 0.031 and 0.049 eV, which provide an excellent charge/discharge rate in anode materials. Furthermore, the theoretical capacity of TiCrC is 479 mAh g–1 when the concentration of Li reaches 2, and TiMoC will exhibit a large theoretical capacity when the open circuit voltage drops to 0 V. In addition, TiCrCO2 exhibits relatively high theoretical capacity (373 mAh g–1). Among all studied materials, pristine TiMC (M = Cr and Mo) and functionalized TiCrCO2 monolayers should be promising candidates as anode materials for LIBs.