A porous material with tailor-made pockets stitched into its structure is a promising material for sensing noxious gases. A thin film of the material, coated onto an electrode, formed an electronic sensor that could detect traces of sulfur dioxide gas1. The sensor is a significant step toward real-world devices that can sniff out dangerous gases in real air.

Although several lab-based analytical instruments can detect traces of a specific gas in the air, these instruments are typically large, expensive, power-hungry machines. There is still a need for small, inexpensive, energy-efficient sensors that, for example, could be widely deployed around industrial sites to continually monitor air quality.

One promising way to make such sensors involves porous materials called metal-organic frameworks (MOFs). By making the MOF from different metal atoms and organic linkers, researchers can create materials that selectively absorb specific gases into tailor-made pockets within the structure. Two KAUST research groups, led by materials scientist, Mohamed Eddaoudi, and electronic engineer, Khaled Salama, recently teamed up to develop MOF-based gas sensors.

The researchers selected an indium-based version of a MOF called MFM-300 as their sensor material. A thin film of the material could be grown onto the electrode under mild conditions that do not damage the sensor circuit. The resulting material forms pockets lined with two -OH groups and four C-H groups that selectively bind sulfur-dioxide molecules. In lab tests using simple mixtures of gases, the sensor could detect sulfur dioxide at concentrations of just a few parts per billion.