Bioinspired molecular recognition via pore confinement and interfacial electric-field regulation in g-C3N5@Zn-TCPP for selective breath ammonia sensing.

Ammonia (NH3) in exhaled breath is a promising biomarker for non-invasive monitoring of metabolic disorders, but achieving selective and sensitive detection under complex breath environments remains challenging. Here, we report a bioinspired g-C3N5@Zn-TCPP heterojunction formed through π-π stacking that enables molecular-recognition-driven breath NH3 sensing. Inspired by the synergistic functions of ammonium transporter (AmtB) and ammonia monooxygenase (AMO), this heterostructure integrates pore-confined molecular enrichment with interfacial electric-field regulation. The intrinsic aperture of Zn-TCPP (∼2.8 Å), closely matching the kinetic diameter of NH3 (2.6 Å), enables size-selective molecular sieving, while the g-C3N5-induced interfacial electric field modulates the electronic environment of Zn2+ active sites and strengthens Lewis acid-base interactions with NH3 molecules. Benefiting from this synergistic molecular recognition mechanism, the optimized 0.08@g-;C3N5@Zn-TCPP sensor achieves a remarkable response (R0/Rg = 223 toward 5 ppm NH3), a low detection limit of 232 ppb, and excellent durability over 1000 bending cycles at room temperature. Machine-learning-assisted analysis further enables accurate discrimination of NH3 from interfering gases (R2 = 0.91). The sensor also distinguishes breath NH3 variations between healthy individuals and disease-related samples, highlighting its potential for intelligent non-invasive breath analysis. This work establishes a bioinspired molecular recognition strategy by coupling pore confinement with interfacial electric-field regulation, providing a new paradigm for selective gas sensing and wearable health-monitoring platforms.