Luis Bartolomé

Heterogeneous lyophobic systems (HLSs) are of interest for diverse applications, including energy materials and column chromatography. Within these systems, tuneability is a key property to broaden the scope of application. In this work, we explore how the exogeneous property of crystallite size can be used to tune in the intrusion–extrusion characteristics of various ZIF MOFs of differing chemistries and topologies. We employ a combination of experimental and in silico techniques to investigate and analyze the behavior of distinct ZIFs during high-pressure water intrusion–extrusion. We observed that ZIF-71, despite differing both chemically and topologically from the previously studied ZIF-8, demonstrated a reduction in intrusion/extrusion pressures and intruded volume with a reduction in crystallite size down to the nanoscale. This was corroborated by a stochastic model of the intrusion of the microporous framework, where control of network size could qualitatively match the experimentally observed behavior. For ZIF-67, the broader distribution of crystallite size led to a staggered intrusion step, which was replicated by the model by averaging the PV-isotherms simulated for various network sizes. These results pave the way for the diversification of HLSs to include the known ZIF family capable of water intrusion–extrusion. Furthermore, controlled crystallite size ranges can be used to mimic the performance of pore size distribution in silica without the inherent associated randomness.

Solid–liquid triboelectric generation is a widespread phenomenon relevant for many natural and technological processes. In particular, solid–liquid triboelectric nanogenerators (TENGs) are an emerging approach for sensing and harvesting dispersed mechanical energy and converting it into electrical power. Triboelectric energy generation relies on charge transfer during contact and separation of different materials, combined with electrostatic induction. Compared with conventional sliding, immersion, or pressing modes, the intrusion–extrusion of liquids into and out of hydrophobic nanopores offers promising advantages, including an enlarged effective contact area and the potential for device miniaturization. However, when water is used as the working liquid, limited charge mobility and weak polarization result in low electrical output. To address these limitations, nanofluids represent a promising alternative. In this work, we investigate how minor concentrations of gold nanoparticles affect triboelectrification during water intrusion–extrusion into-from hydrophobic nanoporous silica. The introduction of gold nanoparticles leads to enhanced triboelectrification and an unexpected reversal of the triboelectric peak polarity. The experimental results indicate that nanoparticle size plays a significant role in determining the electrical response. This approach highlights new opportunities for tuning intrusion–extrusion TENG (IE-TENG) performance and may contribute to the development of advanced sensing and energy-harvesting devices.

Solid–liquid contact electrification is widely studied using diverse experimental geometries that are often implicitly assumed to probe equivalent interfacial processes. Here, we directly test this assumption by comparing immersion–emersion, droplet-based contact, and pressure-driven intrusion–extrusion electrification using the same hydrophobic nanoporous silicon monolith and isotopically substituted liquids (H2O and D2O). Despite identical surface chemistry, isotopic substitution produces qualitatively different electrical responses depending on the wetting regime. Immersion–emersion experiments show polarity inversion between H2O and D2O, while droplet measurements reveal distinct charge evolution and periodic opposite-polarity events. In contrast, forced nanopore intrusion preserves polarity but strongly enhances electrical output for D2O. These results demonstrate that wetting of surface nanoroughness during droplet, vs immersion–emersion, vs complete nanopores wetting upon intrusion–extrusion correspond to fundamentally different electrification states. By using isotope substitution as a controlled probe, this work establishes a general framework for disentangling protocol-dependent effects in solid–liquid contact electrification and triboelectric energy conversion.

The wetting behavior of hydrophobic nanoporous materials plays a pivotal role in advanced technologies such as energy storage, molecular separations, catalysis, and biomimetic systems. A central challenge in employing these materials is the precise control of wetting (intrusion) and dewetting (extrusion) pressures. To address this, we investigated how varying the concentration of organic linkers in ZIF-7-8 (composed of Zn-methylimidazole and benzimidazole) influences the intrusion-extrusion behavior of water within its micropores. Remarkably, we noticed that even a minor substitution of organic linkers (below 3%) led to significant and systematic changes in the wetting properties. Owing to the small fraction of substituted linkers, such effect could not be explained by classical models that consider individual cages. To elucidate this phenomenon, we combined experiments with molecular dynamics simulations and stochastic modeling of the crystallites. Our results reveal that the introduction of alien linkers perturbs the hydrogen-bond network, thereby disrupting the cooperative effects fundamental to the intrusion-extrusion process.

The wetting–dewetting of liquids in nanoporous solids is central to nanofluidics, separation, and energy storage, yet its temperature dependence under extreme conditions remains poorly understood. Here, we investigate water intrusion–extrusion in ordered mesoporous silica (SBA-15) functionalized with octyl groups (SBA-15-C8) across 25–250 °C and compare it with hydrophobized silica of disordered porosity. Intrusion pressures in both systems follow the expected negative temperature dependence described by classical capillarity. In contrast, extrusion pressures reveal a striking topology-temperature interplay. Up to 175 °C, SBA-15-C8 releases water at near-ambient pressure, unlike its disordered counterpart. Above 200 °C, however, extrusion from ordered pores converges to the high-pressure behavior of disordered silica, indicating a loss of topological distinction. Atomistic simulations suggest that this transition originates from thermally induced restructuring of the grafted layer: chain stretching effectively narrows the pores and may induce a Cassie–Baxter-like state, enhancing hydrophobicity and facilitating vapor nucleation. These findings demonstrate that pore topology ceases to govern extrusion at elevated temperatures, instead being dictated by a temperature-driven surface reconfiguration. The results contribute to a fundamental understanding of capillarity under extreme confinement and open opportunities for exploiting high-temperature wetting/dewetting in energy conversion, damping, and thermal management technologies.

The wettability of nanoporous materials is a key property for a diverse range of applications. However, the heat generated in this process remains largely unexplored. Herein, the heats of intrusion/extrusion into/from ZIF-8 + water systems of various ZIF-8 crystallite sizes were measured at different temperatures. We found that decreasing crystallite size to the nanoscale resulted in a reduction of the magnitude of the heats of intrusion/extrusion. These results were mirrored in simulations, where the reduction of intrusion heat by reducing the characteristics dependent on crystallite size was comparable to the values obtained experimentally. We related this to the reduction in filling at lower pressures. We recorded the inversion of the sign of the heats of intrusion/extrusion measured at high temperatures. In addition, the heat/work ratio of the intrusion/extrusion processes was dependent on temperature while independent of crystallite size, decoupling the two parameters and making them tunable exogenously.

Triboelectrification is of great importance for many classical (petroleum, pharmaceutical, polymers) and emerging (generators, sensors) technologies. For energy generation, the contact area between the materials experiencing tribocharging is a key parameter: in addition to the nature of the materials, tribocharging scales with contact area. In this work, an approach is proposed to maximize tribocharging contact area by exploring the cycle of water intrusion–extrusion into–from hydrophobic nanopores with surface area orders of magnitude higher compared to flat or even nanotextured surfaces. Here this study reports the first experimental evidence of electrical energy generation upon water intrusion‐extrusion cycle under bias voltage‐free conditions. Combining these experiments with hierarchical molecular dynamic simulations/ab initio calculations, a microscopic mechanism of triboelectrification is hypothesized for water and grafted silica. The proposed approach provides a methodological alternative to studying solid–liquid contact electrification and an alternative root for a noticeable increase of specific contact area for solid–liquid triboelectric nanogenerators.

Forced wetting (intrusion) and spontaneous dewetting (extrusion) of hydrophobic/lyophobic nanoporous materials by water/nonwetting liquid are of great importance for a broad span of technological and natural systems such as shock-absorbers, molecular springs, separation, chromatography, ion channels, nanofluidics, and many more. In most of these cases, the process of intrusion-extrusion is not complete due to the stochastic nature of external stimuli under realistic operational conditions. However, understanding of these partial processes is limited, as most of the works are focused on an idealized complete intrusion-extrusion cycle. In this work, we show an experimental system operating under partial intrusion/extrusion conditions and present a simple model that captures its main features. We rationalize these operational conditions in terms of the pore entrance and cavity size distributions of the material, which control the range of intrusion/extrusion pressures.