Layer-by-layer assembled dual-ligand conductive MOF nano-films with modulated chemiresistive sensitivity and selectivity

In this paper, a dual-ligand design strategy is demonstrated to modulate the performance of the electronically conductive metal-organic frameworks (EC-MOFs) thin film with a spray layer-by-layer assembly method. The thin film not only can be precisely prepared in nanometer scale (20-70 nm), but also shows the pin-hole-free smooth surface. The high quality nano-film of 2,3,6,7,10,11-hexaiminotriphenylene (HITP) doped Cu-HHTP enables the precise modulation of the chemiresistive sensitivity and selectivity. Selectivity improvement over 220% were realized for benzene vs. NH₃, as well as enhanced response and recovery properties. In addition, the selectivity of the EC-MOF thin film sensors toward other gases (e.g. triethylamine, methane, ethylbenzene, hydrogen, butanone, and acetone) vs. NH₃ at room temperature is also discussed.