A novel N,S-rich COF and its derived hollow N,S-doped carbon@Pd nanorods for electrochemical detection of Hg2+ and paracetamol

Highlights: • A new N,S-rich covalent-organic framework (COF_BTT-TZT) is prepared. • A Hg²⁺ sensor is developed based on COF_BTT-TZT. • Using COF_BTT-TZT as precursor and template, hollow N,S-doped C@Pd nanorods is obtained. • An electrochemical paracetamol sensor is proposed based on N,S-doped C@Pd nanorods. • The sensors exhibited good performances for Hg²⁺ and paracetamol. Covalent-organic frameworks (COFs) are conjugate crystalline polymers with high porosity, controllable pores and structure as well as large specific surface area, showing great potential for electrochemical sensors. Here, a new N,S-rich COF_BTT-TZT is proposed by direct amine-aldehyde dehydration condensation between 4,4',4′'-(1,3,5-triazine-2,4,6-triyl)trianiline (TZT) and benzo [1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde (BTT). The COF_BTT-TZT has a hexagonal hcb structure with theoretical pore of 2.2 nm and presents rod-like morphology with many small flakes on its surface. Particularly, there are lots of S and N atoms in COF_BTT-TZT, which provides abundant adsorption sites for Hg²⁺ so that it can be used to detect Hg²⁺. The proposed Hg²⁺ sensor has a linear range of 0.54 nM–5.0 μM and a detection limit of 0.18 nM. Besides, using COF_BTT-TZT as precursor and template, the hollow N,S-doped C@Pd nanorods which possesses many tiny Pd nanoparticles embedded in rods-like hollow structure are obtained. An electrochemical paracetamol sensor is also proposed based on the N,S-doped C@Pd nanorods, showing low detection limit of 11 nM and wide linear range of 33 nM–120 μM. The good results provide an important guidance for the application of COF in electrochemical sensors.