Advance sensing of high energy explosive: A DFT-Based study of C₅N framework performance

The detection of explosive materials is essential for environmental safety, and military monitoring. In this work, a pyridine-based C₅N covalent framework surface was investigated as a sensing material for the detection of explosive molecules FOX-7, H-FOX, LLM-16, and TATB using density functional theory (DFT) calculations. Evaluation of the electronic properties was done by natural bond orbital (NBO), electron density difference (EDD), frontier molecular orbital (FMO) and density of states (DOS) analyses. The calculated interaction energies reveal that TATB and H-FOX exhibit stronger adsorption on the C₅N surface, while LLM-16 shows relatively weaker interaction. NCI and QTAIM analyses confirm that the adsorption is dominated by weak noncovalent interactions such as van der Waals forces and π-π interactions. Charge transfer from the C₅N surface to the analytes is confirmed through NBO and EDD analyses. FMO and DOS results indicate a reduction in the HOMO-LUMO energy gap upon adsorption, demonstrating improved conductivity and sensing capability of the C₅N surface. Among the studied analytes, LLM-16 shows the largest reduction in the energy gap, suggesting the highest sensing sensitivity. Furthermore, recovery time calculations indicate rapid desorption behavior, highlighting the reusability of the sensor. Overall, the results suggest that the C₅N surface is a promising sensing material for the efficient detection of explosive molecules.