Scalable Melt Polymerization Synthesis of Covalent Organic Framework Films for Room Temperature Low-Concentration SO₂ Detection

The development of highly efficient sensors for low-concentration SO₂ at room temperature is important for human health and fine chemistry, but it still faces critical challenges. Herein, a scalable olefin-linked covalent organic framework (COF) with an ultramicroporous structure and abundant binding sites is first developed as the SO₂ sensing material. The COF can adsorb SO₂ of 220 cm³/g at 1 bar and 40 cm³/g at 0.01 bar and 298 K, surpassing all reported COFs. The computational and kinetic adsorption studies deeply unveil the selective adsorption mechanism for low-concentration SO₂. Furthermore, the multicomponent gas mixture breakthrough experiments confirm that the COF can specifically capture low-concentration (2000 ppm) SO₂. We innovated a melt polymerization technology to fabricate COF films with adjustable substrates and film thicknesses. COF films are directly grown on the interdigital electrodes to prepare the SO₂ sensor device, which possesses a low detection limit (86 ppb) and excellent selectivity for SO₂ in the presence of 10 other potentially interfering gases. Compared to other reported SO₂ sensors, its overall performance is among the top. Prominently, the sensor maintains a stable output signal for more than two months, and recovery can be easily achieved by simply purifying nitrogen at room temperature without heating. This study marks the first use of COFs for SO₂ sensing, opening new possibilities for COFs in the detection of low-concentration toxic gases and manufacturing gas sensor devices.