Multicomponent tandem polymerization for the preparation of a pyrazole-containing porous organic polymer for iodine capture and the nitro reduction reaction

Abstract

Developing a straightforward and efficient strategy for incorporating functionality in porous materials is of paramount importance. Functionality can endow these materials with enhanced performance in established applications or enable new performances in emerging application domains. Herein, we present the synthesis of a pyrazole-containing porous organic polymer (PPOP) via a multicomponent tandem polymerization reaction involving tetrakis(4-ethynylphenyl)silane, terephthaloyl chloride, and hydrazine hydrate. The integration of pyrazole units into a porous network bestows new functionality on PPOP and leads to excellent iodine capture performance and suitable support for silver nanoparticles, which can act as an efficient catalyst for nitro reduction reactions. PPOP exhibits an iodine vapor adsorption capacity of 3.52 ± 0.15 g g⁻¹, which is comparable to or higher than many existing iodine adsorbents. Mechanistic investigations reveal that the adsorption is governed by a combination of physisorption and chemisorption. Chemisorption is facilitated by electron transfer from electron-rich moieties, particularly pyrazole groups, within the adsorbent to I₂, leading to the formation of polyiodides and charge-transfer complexes. When loaded with silver nanoparticles, PPOP can catalyze the reduction reactions of nitroaromatics to aminoaromatics with nearly complete conversion within 20 min at room temperature. This research underscores the utility of multicomponent tandem polymerization reactions for the rational design and synthesis of functional POPs with potential applications in diverse fields.