One-step preparation of nanobeads-based polypyrrole hydrogel by a reactive-template method and their applications in adsorption and catalysis

In this manuscript, nanobeads-based polypyrrole (PPy) hydrogel was prepared by a reactive-template method in one-step. Fe₃O₄ nanoparticles were selected as reactive-templates, which not only acted as the oxidants to initiate polymerization of pyrrole monomer, but also guided the growth of polymer chains. No surfactants were involved in whole preparation procedure, leading to a superior purity of products. Because PPy hydrogels were obtained by cross-linking individual nanobeads, they have bridged nano-dimension and macro-dimension together; thus displayed a three-dimensional hierarchical porous structure. By taking advantage of structural merits, PPy hydrogels exhibited large surface area and plenty of interconnected channels, which made them act as good candidates for adsorbents of rhodamine B (RhB). During the adsorption experiment, their adsorption kinetics were carefully investigated. In comparison tests, their equilibrium adsorption capacities were higher than that of referenced PPy (R-PPy) hydrogels prepared by a classical oxidation polymerization. In addition to be used as adsorbent, PPy hydrogels could serve as support to load Pd nanoclusters. During the catalytic reduction of RhB with NaBH₄ as reducing agent under the same Pd loadings, PPy/Pd hydrogels displayed better catalytic activity than that of R-PPy/Pd hydrogels, and their rate constant and turnover frequency was 12 and 4.8 times higher than that of the latter.