Facile synthesis of hyperbranched Eu-MOF structures for the construction of a CsPbBr3/Eu-MOF composite and its application as a ratiometric fluorescent probe

CsPbBr3 nanocrystals (NCs) exhibit great potential for various optoelectronic applications due to their excellent optoelectrical properties. However, the poor stability inherited from the ionic crystal structure limits their practical applications. Hence, coupling CsPbBr3 NCs with protective and functional materials for achieving superior properties is one of the current research challenges. Herein, three-dimensional hyperbranched structures of Eu-MOF were developed as effective frameworks coupled with CsPbBr3 NCs. Rich Eu-MOF morphologies including sheaf-like, dumbbell-like, and urchin-like ones were achieved in a controllable way via introducing an Al(Ac)3 additive. The crystal splitting growth mechanism was found to dominate the formation of hierarchical Eu-MOF structures, as evidenced by the time-dependent morphological evolution of an urchin-like Eu-MOF. In addition, acidic carboxylate salts (such as Al(Ac)3, Zn(Ac)2, Pb(Ac)2, Cu(Ac)2, Ni(Ac)2) effectively modulate the splitting of Eu-MOF crystal growth, which is deemed to be the synergistic effect of metal ions and acetate ions. Subsequently, a series of CsPbBr3/Eu-MOF composites were synthesized by pre-preparing various Eu-MOF hyperbranched structures, and they demonstrate excellent dual-emissive optical properties. A ratiometric fluorescence probe fabricated by encapsulating CsPbBr3 in the three-dimensional hyperbranched Eu-MOF structure exhibits remarkable sensitivity, good linearity, and high selectivity for DMF detection.