Detection of Harmful Gases by Copper-Containing Metal–Organic Framework Films

The stabilization of copper clusters in nanosized metal–organic framework crystals, Cu-Y­(BTC), was achieved by a solvent-exchange approach, followed by hydrogen reduction. The formation of copper clusters in the Y­(BTC) nanocrystals generated during the hydrogen reduction process was followed by UV–vis spectroscopy. The Cu-Y­(BTC) nanocrystals were further assembled in thin films with a thickness of 250 nm. The distribution and size of the copper clusters in the films were studied by CO chemisorption, followed by FT-IR spectroscopy combined with transmission electron microscopy. It was shown that the copper clusters with a mean diameter of 6 nm were homogeneously distributed and stabilized in the Cu-Y­(BTC) films. Further, the Cu-Y­(BTC) films were utilized for detection of single harmful gases, such as CO, chloroform, and 2-ethylthiophene, or mixtures of two compounds. The high sensitivity, selectivity, and reversibility of the Cu-Y­(BTC) films toward single CO, chloroform, and 2-ethylthiophene were demonstrated. Noteworthy, the Cu-Y­(BTC) films exhibited a fast response toward CO, even in the presence of chloroform and 2-ethylthiophene, which was due to the high activity and accessibility of copper clusters. The response of Cu-Y­(BTC) toward 2-ethylthiophene was slower in comparison with chloroform, which was attributed to the bigger size and higher viscosity of 2-ethylthiophene

Gas Analysis by Electron Ionization Combined with Chemical Ionization in a Compact FTICR Mass Spectrometer

In this Article, a compact Fourier transform ion cyclotron resonance (FTICR) mass spectrometer based on a permanent magnet is presented. This instrument has been developed for real-time analysis of gas emissions. The instrument is well-suited to industrial applications or analysis of toxic and complex samples where the concentrations can vary rapidly on a wide range. The novelty of this instrument is the ability to use either electron ionization (EI) or chemical ionization (CI) individually or both of them alternatively. Also in CI mode, different precursor ions can be used alternatively. Volatile organic compounds (VOCs) from the ppb level to very high concentrations (% level) can be detected by CI or EI. The magnet is composed of three Halbach arrays, and the nominal field achieved is 1.5 T. The ICR cell is a 3 cm side length cubic cell. The mass range is 12–200 u with a broad band detection. The mass accuracy of 0.005 u and the resolving power allow the separation of isobaric ions such as C₃H₈⁺ and CO₂⁺. Gas introduction via controlled gas pulses, electron ionization, ion–molecule reactions, ion selection, and detection are all performed in the ICR cell. The potential of the instrument will be illustrated by an analysis of a gas mixture containing trace components at ppm level (VOCs) and components in the 0.5–100% range (N₂, alkanes, and CO₂)