In this article, the effect of a porous material’s flexibility on the dynamic reversibility of a nonwetting liquid intrusion was explored experimentally. For this purpose, high-pressure water intrusion together with high-pressure in situ small-angle neutron scattering were applied for superhydrophobic grafted silica and two metal–organic frameworks (MOFs) with different flexibility [ZIF-8 and Cu2(tebpz) (tebpz = 3,3′,5,5′tetraethyl-4,4′-bipyrazolate)]. These results established the relation between the pressurization rate, water intrusion–extrusion hysteresis, and porous materials’ flexibility. It was demonstrated that the dynamic hysteresis of water intrusion into superhydrophobic nanopores can be controlled by the flexibility of a porous material. This opens a new area of applications for flexible MOFs, namely, a smart pressure-transmitting fluid, capable of dissipating undesired vibrations depending on their frequency. Finally, nanotriboelectric experiments were conducted and the results showed that a porous material’s topology is important for electricity generation while not affecting the dynamic hysteresis at any speed.

Negative thermal expansion (NTE) is the process in which a system decreases its size upon heating and increases it upon cooling. NTE effect is unusual and useful for a great number of practical applications in the fields of electronics, medicine, mechanics, etc. In this work, NTE effect is experimentally investigated for three porous Heterogeneous Lyophobic Systems (HLS), associating water and two grafted mesoporous silicas or the microporous metal−organic framework ZIF-8. Considerable NTE effect, more than 1 order of magnitude higher than best-known materials, is observed for these systems. Additionally, it is demonstrated that for HLS, the temperature range in which NTE takes place is easily controlled by basic characteristics of the porous solid such as pore size distribution.

On-demand access to renewable and environmentally friendly energy sources is critical to address current and future energy needs. To achieve this, the development of new mechanisms of efficient thermal energy storage (TES) is important to improve the overall energy storage capacity. Demonstrated here is the ideal concept that the thermal effect of developing a solid–liquid interface between a non-wetting liquid and hydrophobic nanoporous material can store heat to supplement current TES technologies. The fundamental macroscopic property of a liquid’s surface entropy and its relationship to its solid surface are one of the keys to predict the magnitude of the thermal effect by the development of the liquid–solid interface in a nanoscale environment—driven through applied pressure. Demonstrated here is this correlation of these properties with the direct measurement of the thermal effect of non-wetting liquids intruding into hydrophobic nanoporous materials. It is shown that the model can resonably predict the heat of intrusion into rigid mesoporous silica and some microporous zeolite when the temperature dependence of the contact angle is applied. Conversely, intrusion into flexible microporous metal–organic frameworks requires further improvement. The reported results with further development have the potential to lead to the development of a new supplementary method and mechanim for TES.

Controlling the pressure at which liquids intrude (wet) and extrude (dry) a nanopore is of paramount importance for a broad range of applications, such as energy conversion, catalysis, chromatography, separation, ionic channels, and many more. To tune these characteristics, one typically acts on the chemical nature of the system or pore size. In this work, we propose an alternative route for controlling both intrusion and extrusion pressures via proper arrangement of the grains of the nanoporous material. To prove the concept, dynamic intrusion−extrusion cycles for powdered and monolithic ZIF-8 metal−organic framework were conducted by means of water porosimetry and in operando neutron scattering. We report a drastic increase in intrusion−extrusion dynamic hysteresis when going from a fine powder to a dense monolith configuration, transforming an intermediate performance of the ZIF-8 + water system (poor molecular spring) into a desirable shockabsorber with more than 1 order of magnitude enhancement of dissipated energy per cycle. The obtained results are supported by MD simulations and pave the way for an alternative methodology of tuning intrusion−extrusion pressure using a macroscopic arrangement of nanoporous material.

The work presents an ecological vehicle, which is a touring bicycle with the compact hydraulic system based on the hydraulic / thermomolecular accumulator. Due to the hydrosystem, the cyclist has the ability to store mechanical / hydraulic energy by pedaling during downhill, which is used when moving uphill without pedaling. The prototype was designed some time ago at the Laboratory of Thermomolecular Energetics (TME) of the Igor Sikorsky Kyiv Polytechnic Institute. In order to improve the vehicle technical characteristics, it is proposed to replace the traditional pneumohydraulic accumulator (PHA) with the thermomolecular analogue. The comparative analysis of the vehicle operation with each type of accumulator is carried out.