UNAM-3: A soft hybrid inorganic-organic material with self-healing properties, solvent adaptability and electrical conductivity

The structural adaptability of porous materials provides a versatile platform for designing systems for multifaceted applications, such as adsorption and sensing. In hybrid materials, integrating this dynamic behavior with the functional properties of inorganic and organic building blocks can lead to multifunctional materials. This work presents UNAM-3 , a new inorganic-organic hybrid material with solvent-exchangeable porosity based on the stable and redox-active Keggin polyoxometalate [SiW 12 O 40 ] 4– and the dimeric radical-cation of N,N,N′,N′-tetraethylbenzidine ([TEB ⦁+ ] 2 ). These charged molecules assemble via electrostatic and nonclassical hydrogen-bond interactions into a 3D network with 1D channels capable of reversibly exchange dimethyl sulfoxide, dichloromethane, tetrahydrofuran, toluene, methanol, and acetonitrile, by dynamically modulating the framework's volume and symmetry as a function of the solvent's size. Additionally, UNAM-3 exhibits an electrical conductivity of 4.24 x 10 −7 S cm −1 . To define the role of each building block, we synthesized two additional hybrid materials: a precursor of UNAM-3 comprising the protonated TEBH 2 2+ and the Keggin anion (compound 1 ), and [TEB ⦁+ ] 2 [I 3 − ] 2 , a non-porous hybrid material with a conductivity of 1.38 x 10 −8 S cm −1 . The latter comparison underscores the polyoxometalate's dual role in enabling porosity and enhancing conductivity. The robust electrostatic nature of the network, together with its intrinsic porosity, is responsible for its flexibility and self-healing.