Adjusting the Stacking Model of Two-Dimensional Covalent Organic Frameworks for Volatile Acid Sensing via Spatial Effects

Covalentorganic frameworks (COFs) are polymer networks with aprecise structure and permanent porosity, making them an attractiveplatform for the detection of volatile analytes due to their chemicalstability and accessible active sites. In this study, based on electron-rich N,N,N & PRIME;,N & PRIME;-tetrakis(4-aminophenyl)-1,4-benzenediaminemoiety, two 2D COFs with different topological structures and stackingmodels were designed by the strategy of spatial effect. The conductivityof the AB-stacked COF-NUST-20 was an order of magnitude higher thanthat of the AA-stacked COF-NUST-30. With the protonation of the iminebond, both COFs exhibited a strong, rapid, and reversible visiblecolor change in response to corrosive HCl vapor. In addition, theAB-stacked COF-NUST-20, which facilitates both interlayer and intralayercharge transfer, shows better sensing performance. These findingsdemonstrate the usefulness of all-aromatic 2D COFs as real-time responsivechemosensors and provide insight into the design of sensing materialswith high sensitivity.