Compact Thermal Actuation by Water and Flexible Hydrophobic Nanopore

Abstract

Efficient and compact energy conversion is at the heart of the sustainable development of humanity. In this work it is demonstrated that hydrophobic flexible nanoporous materials can be used for thermal-to-mechanical energy conversion when coupled with water. In particular, a reversible nonhysteretic wetting-drying (contraction-expansion) cycle provoked by periodic temperature fluctuations was realized for water and a superhydrophobic nanoporous Cu₂(tebpz) MOF (tebpz = 3,3',5,5'-tetraethyl-4,4'-bipyrazolate). A thermal-to-mechanical conversion efficiency of ∼30% was directly recorded by high-precision <i>PVT</i>-calorimetry, while the operational cycle was confirmed by <i>in operando</i> neutron scattering. The obtained results provide an alternative approach for compact energy conversion exploiting solid-liquid interfacial energy in nanoscopic flexible heterogeneous systems.