Solution-processed lead-free halide perovskite gas sensors possess low gas detection limits, offering promising alternatives to traditional metal oxide chemiresistors. However, halide perovskite chemiresistors often suffer from poor selectivity and durability due to a lack of coordinatively unsaturated surface metal ions and their sensitivity to humidity. To address these issues, a general strategy is presented in which the Cs₂PdBr₆ perovskite surface is coated with covalent organic framework (COF) to provide hybrid sensor materials that are highly sensitive to specific gases and demonstrate excellent stability under real-working conditions. The hybrid chemiresistors demonstrate high sensitivity and controllable selectivity toward NO₂ or NH₃ gases. Specifically, TAPB–PDA@Cs₂PdBr₆ achieves a detection limit of 10 ppb for NO₂, the lowest value reported for a perovskite-based gas sensor, maintaining its performance after continuous exposure to ambient air for several weeks. In contrast, COF-5@Cs₂PdBr₆ shows high selectivity to NH₃ and has a detection limit of 40 ppb. Structural and spectroscopic characterization combined with mechanistic studies provide molecular-level insights into the outstanding properties of these new hybrid sensor materials, which set a new benchmark in the field, i.e., surpassing the selectivity and sensitivity of conventional halide perovskite sensors.

中文翻译：

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共价有机框架增强型金属卤化物钙钛矿，用于选择性和灵敏气体传感


溶液处理的无铅卤化物钙钛矿气体传感器具有较低的气体检测限，为传统的金属氧化物化学电阻器提供了有前途的替代品。然而，由于缺乏配位不饱和表面金属离子及其对湿度的敏感性，卤化物钙钛矿化学电阻器通常具有较差的选择性和耐用性。为了解决这些问题，提出了一种通用策略，其中 Cs₂PdBr₆ 钙钛矿表面涂有共价有机框架 （COF），以提供对特定气体高度敏感并在实际工作条件下表现出出色稳定性的混合传感器材料。混合化学电阻器对 NO₂ 或 NH₃ 气体表现出高灵敏度和可控选择性。具体来说，TAPB–PDA@Cs₂PdBr₆ 对 NO₂ 的检测限为 10 ppb，这是基于钙钛矿的气体传感器报告的最低值，在连续暴露于环境空气中数周后仍能保持其性能。相比之下，COF-5@Cs₂PdBr₆ 对 NH₃ 具有高选择性，检测限为 40 ppb。结构和光谱表征与机理研究相结合，为这些新型混合传感器材料的出色特性提供了分子水平的见解，这在该领域树立了新的标杆，即超越了传统卤化物钙钛矿传感器的选择性和灵敏度。