Single-Step Laser Direct Writing of MOF-5 and Graphitic Carbon Bilayer Microstructures for CO₂ Sensing

Metal-organic frameworks (MOFs) have attracted considerable interest as adsorbent materials because of their high molecular adsorption capability. To fully utilize these properties in electrically operable microstructures, integration with conductive structures is essential, as it addresses the inherent electrical limitations of MOFs. Conventional approaches for fabricating MOF-integrated electrically conductive structures typically require separate steps for material synthesis, patterning, and integration with conductive structures. In this study, we demonstrate single-step laser direct writing of arbitrarily patterned microstructures composed of MOF-5 and graphitic carbon for CO₂ sensing. The laser process forms MOF-5, which has been reported to exhibit CO₂ adsorption capability, together with conductive graphitic carbon within a single written microstructure, eliminating the need for separate fabrication and integration steps. The fabricated microstructures exhibit resistance changes upon CO₂ adsorption by MOF-5, while the incorporated graphitic carbon generates Joule heating under applied voltage, thereby promoting desorption of the adsorbed CO₂. These results indicate that single-step laser direct writing is a promising strategy for fabricating MOF-integrated microstructures that combine adsorption capability with electrical conductivity, providing a basis for broader integration of MOFs into functional microscale devices.