Unveiling the catalytic potency of a novel hydrazone-linked covalent organic framework for the highly efficient one-pot synthesis of 1,2,4-triazolidine-3-thiones†

A novel hydrazone-linked covalent organic framework (TRIPOD-DHTH COF) was synthesized through the ultrasonic treatment of 2,5-dihydroxyterephthalohydrazide (DHTH) and 4,4′,4′′-[1,3,5-triazine-2,4,6-triyltris(oxy)]tris-benzaldehyde (TRIPOD). The COF was extensively analyzed using FT-IR, PXRD, SEM, TEM, BET, XPS, TGA, and DTA techniques. The characterization studies revealed the presence of mesoporous properties and high thermal stability, with a surface area measuring 2.78 m² g⁻¹ and an average pore size of 8.88 nm. The developed COF demonstrated exceptional catalytic activity in synthesizing 1,2,4-triazolidine-3-thiones from thiosemicarbazide and various ketones and aldehydes using a water : ethanol (1 : 2) medium at room temperature. A significant yield (80–98%) of 1,2,4-triazolidine-3-thiones was obtained in a low reaction time (4–20 min). The role of TRIPOD as a precursor in the synthesis of the COF and as a reactant in the synthesis of 1,2,4-triazolidine-3-thione (3l) was found to be fascinating. The synthesized COF maintained its catalytic activity over eight runs, underscoring its efficiency and reusability, highlighting its potential for sustainable chemical syntheses.