Planar Polymer Optical Waveguide with Metal‐Organic Framework Coating for Carbon Dioxide Sensing

An easily fabricated gas sensor based on planar polymer optical waveguides with an integrated zeolite imidazole framework‐8 (ZIF‐8) thin film is presented for carbon dioxide detection and sensing. The planar optical waveguides are made of polymethylmethacrylate and fabricated by hot embossing, which makes it flexible and cost‐efficient. Thin ZIF‐8 films are uniformly grown on the waveguides surface through a simple solution method, which is crucial for the envisioned production of metal organic framework‐based sensing devices on a large scale. Experimental results show that the produced optical elements exhibit a sensitivity of ≈2.5 μW/5 vol% toward carbon dioxide (CO2) with very rapid response time (≈6 s) and excellent reversibility of adsorption and desorption of the gas molecules. The demonstrated planar polymer sensing devices provide the potential to develop flexible on‐chip gas sensors in an inexpensive and reproducible way.