Phosphotungstic acid-doped covalent triazine framework as a bifunctional heterogeneous catalyst for one-pot multicomponent synthesis of spiro-quinazolinones under green reaction conditions

Abstract

Functionalized covalent triazine frameworks have emerged as nitrogen-rich porous materials with abundant functional moieties that enable uniform and stable immobilisation of active species for heterogeneous catalysis. Herein, we report a facile approach to introduce bifunctionality into a porous triazine framework via post-synthetic doping, involving the incorporation of phosphotungstic acid into a piperazine–cyanuric chloride-based COF. The resultant bifunctional catalyst, PTA@PC-COF, demonstrated excellent performance in the tandem one-pot multicomponent synthesis of spiro-quinazolinones, with a high turnover frequency (TOF) of 395.50 h⁻¹. The reaction afforded an excellent yield of the desired products (87–96%) within a very short reaction time (5–12 min) under green reaction conditions. The catalyst was comprehensively characterised using various spectroscopic techniques, including BET, SEM, PXRD, FT-IR, XPS, elemental mapping, and TGA. The material PTA@PC-COF exhibited high thermochemical stability and good recyclability over seven consecutive runs with negligible loss in catalytic efficiency, underscoring its potential as a sustainable catalytic system for green, scalable organic synthesis of spiro-quinazolinones.