Hydrophobic functionalization of a metal–organic framework as an ammonia visual sensing material under high humidity conditions

Abstract

Since exhaled ammonia (NH₃) is one of the metabolic markers of liver and kidney diseases, ammonia visual sensing materials in humid environments have received extensive attention and investigation. Herein, through a tailor-made pore environment provided by metal–organic framework (MOF) materials (CH₃-Cu(BDC)), we achieved NH₃ anti-interference sensing with apparent color changing under humid conditions. With methyl (CH₃–) functionalization, CH₃-Cu(BDC) demonstrated a strong response for trace ammonia and showed high selectivity under a humid environment. Grand canonical Monte Carlo (GCMC) simulations indicated that CH₃-Cu(BDC) showed stronger attraction towards NH₃ molecules than H₂O. Benefiting from the target changing coordination environment, CH₃-Cu(BDC) showed a rapid response and simple analysis properties for patients’ exhaled air. The strategy used in this study not only provides a demonstration case for NH₃ colorimetric sensing with high humidity and anti-interference but also introduces a new method for painless and quick exhaled breath analysis for diagnosis of patients with kidney and liver diseases.