Developing a binary composite of covalent organic framework and gold microstructures: Highly efficient dual-mode catalyst for analysis of nitrophenol isomers and their oxidative products

As a key hazard, nitrophenol and its byproducts are a vital raw material in the industry and potentially released into aquatic environments, which affects the ecosystem and severely threatens living systems. It is crucial to detect nitro-hazards quantitatively and systematically. The unique structures of isomer separation and catalytic reduction are highly complex in a single system, not yet reported detection method. The present report constructed robust gold-microstructures (AuMSs) with bis-triazole-derived covalent organic framework (BTCOF) was developed to analyze the dual-mode application of electrochemical redox signals and catalytic degradation of nitrophenol isomers (NPIs) and their oxidative products. The synergistic interaction of tunable surfaces on binary materials enhanced catalytic efficiency, faster kinetic rates, and poor passivation. Based on the variance in pKa values, both NPIs and nitrosophenols (NSPIs) could be identified, peak separated, and sensed simultaneously. A catalyst combined with NaBH4, enabled NPIs reduction within ten minutes. This proposed electrochemical method achieved a nanomolar LOD (1.82, 1.67, and 1.15 × 10-9 M for o-, m-, and p-NPs), excellent sensitivity to ultrawide linear concentrations while being selective, and reproducible. Moreover, AuMSs-BTCOF/GCE detected NPIs in the industrial effluents and biofluids samples with recovery rates between 94.70-99.95 ± 0.18% with RSD < 3%. The electrochemical result was validated by conventional method with proven statistical analysis (error < 4.0%). In the catalytic reduction of NPIs, the catalyst is more than 89.24% efficient, and durable stability. The designed system has proven to be an effective, sensitive, and accurate dual-detection tool for monitoring environmental targets and diagnosing diseases.