Spin-Crossover in an Exfoliated 2D Coordination Polymer and Its Implementation in Thermochromic Films

Abstract

Development of novel 2D materials with singular and thrilling properties has aroused large interest due to the novel unexpected applications that can be derived from there. In this sense, coordination polymers (CPs) have appeared as matching candidates thanks to their rational chemical design and the added-value properties given by the presence of metal ions. This is the case of switchable spin crossover systems that have been proposed as excellent candidates for data storage or sensing, among others. Here we report the delamination of crystals of the 2D spin crossover (SCO) {[Fe(L1)2](ClO4)2}∝ (1) CP by liquid-phase exfoliation (LPE) in water. The application of this top-down technique results in the formation of flakes with controlled thicknesses, down to 1-2 nm thick (mostly mono-and bi-layer), that retain the chemical composition and SCO interconversion of the bulk material. Moreover, these flakes can be handled as stable colloidal dispersions for many days. This allows for a controlled transfer to solid substrates and the formation of thermochromic polymeric films as a proof-of-concept of device. These first results will definitely open new venues and opportunities for the investigation and future integration of these original switchable 2D materials in devices.

Ultrasound-assisted exfoliation of a layered 2D coordination polymer with HER electrocatalytic activity

“…This result, together with other studies [21] , [22] , [16] , [17] , [23] , [24] , has clearly demonstrated the importance of properly selecting the mixture of solvent and ultrasounds for a good delamination process. Overall, seemly candidates for LPE processes present weak interactions between layers due to occluded interlayer molecules that can be easily uninvolved under sonication in the appropriate solvent [25] .…”

Realization of reversible thermochromic polydiacetylene through silica nanoparticle surface modification

“…15,16 Metal thermochromic materials undergo color transition with the variation of temperature attributable to changes in crystal lattice, ligand geometry and crystal water. [17][18][19] Once thermochromic materials experience irreversible changes due to oxidation, decomposition or melting in physical or chemical properties during the heating process, the chromatic behavior will be unidirectional that the material cannot recover its primary color after cooling. The using efficiency of thermochromic material will be reduced.…”

Delamination of 2D coordination polymers: The role of solvent and ultrasound

“…In addition to its rich chemical flexibility, 2D-CPs contain metallic ions that confer novel optical, magnetic and/or electrical properties [4]. All these premises have already crystallized in different examples of 2D materials relevant for the electrochemical detection of H2O2 [5], functional thin films [6], molecular sieve membranes [7], polymer composites for gas separation [8][9], catalysis [10][11], photoluminescence [12][13], or several electronic applications [14] such as field effect transistors [15], chemoresistive gas sensors [16] including e-textiles [17], electrochemical oxygen reduction catalysts [18], supercapacitors [19][20][21] or spin-cross over systems [22].…”