A nanocomposite gel based on 1D coordination polymers and nanoclusters reversibly gelate water upon heating

Abstract

A stable nanocomposite metallogel was obtained by the addition of [Na(L)(H₂O)]·2H₂O (HL = 4,6-bis(2-pyridyl)-1,3,5-triazin-2-ol) to an aqueous solution of Cu₂(OAc)₄·2H₂O in a molar ratio of Cu/L = 4 (5.6 wt% gelator concentration), from which 1D coordination polymers [Cu₂L(μ-OAc)₂(μ-OH)] (1) and coordination nanoclusters {[Cu₉L₄(OAc)₇(OH)₅]²⁺}₂ (3) were afforded. The nanoclusters 3 stabilize the 1D coordination polymers 1 and inhibit crystallization of 1 from the system, generating a coordination-based heat-set nanocomposite hydrogel at room and higher temperatures that flows upon cooling to 4 °C, in sharp contrast to most supramolecular gels. Reversible thermo and pH responsive solution–gel phase transitions were observed. The results described herein may open a novel avenue for functional coordination nanocomposite materials.