Thermal-Responsive Polyoxometalate-Metalloviologen Hybrid: Reversible Intermolecular Three-Component Reaction and Temperature-Regulated Resistive Switching Behaviors.

The development of new-type memristors with special performance is of great interest. Herein, an inorganic-organic hybrid crystalline polyoxometalate (POM) with usual dynamic structures is reported and used as active material for fabricating memristor with unique temperature-regulated resistive switching behaviors. The hybrid POM not only exhibits tunable thermochromic properties, but also thermal-induced reversible aggregation and disaggregation reactions, leading to reversible structural transformations in SCSC fashion. Further, the memory device using the hybrid POM as active layer exhibits uncommon performance, which can keep resistive switching silent in the low temperature range of 30-150 °C, but show nonvolatile memory behavior in the high temperature range of 150-270 °C. Particularly, the silent and working states at three special temperatures (30, 150 and 270 °C) can be monitored by chromism. The correlation between structure and resistive switching property of the material has been discussed. The work demonstrates that crystalline inorganic-organic hybrid POMs are promising materials for making memristors with superior performance.

Encapsulating Halometallates into 3-D Lanthanide-Viologen Frameworks: Controllable Emissions, Reversible Thermochromism, Photocurrent Responses, and Electrical Bistability Behaviors.

The encapsulation of guests into metal-organic frameworks (MOF) is an efficient strategy to generate novel multifunctional materials with enhanced properties. Herein, four halometallate@MOF composites with formulas of {(Pb2I4Br3)[(Pr(bpdo)4(H2O)2]·(H2O)}n (1), {[Pb3I10(H2O)2][Y2(bpdo)5(OH)2]·4(H2O)}n (2), {(Bi2I9)[(Pr(bpdo)3(H2O)]}n (3), {(Bi4I18)[(La(bpdo)4(H2O)2]2}n (4) (bpdo = 4,4'-bipyridine N,N'-dioxide) were prepared. In these composites, lanthanide-viologen MOF act as matrices, whose cavities were penetrated by halometallates. Consequently, the insertion of electron-rich halometallates into electron-deficient lanthanide-viologen matrices leads to the presence of strong room temperature charge transfer (CT) interactions. Importantly, these composites exhibit enhanced photo/thermal stabilities, controllable white emissions, reversible thermochromisms, and good photocurrent response performances. Specially, the memory devices based on these composites illustrate reversible electrical bistability behaviors, which can be assigned to ohmic and space-charge-limited conduction (SCLC) mechanisms. This kind of composite can be utilized as a multifunctional platform with enhanced stability.