arXiv subjects

J. M. Vicent-Luna

Publications and source records attributed to J. M. Vicent-Luna.

8 recordsLinked to original sources

arXiv2026

Influence of Ultramicroporosity and Surface Chemistry on Dynamic CO2 Capture in Activated Carbons

Activated carbons are promising adsorbents for post-combustion CO2 capture due to their high surface area, tunable microporosity, and resistance to moisture and flue-gas impurities. Despite extensive equilibrium adsorption studies, the dynamic behavior of activated carbons under fixed-bed operating conditions relevant to post-combustion CO2/N2 remains insufficiently understood, particularly for renewable materials. In this work, the adsorption and separation behavior of CO2/N2 mixtures on a commercial coal-derived activated carbon (WS-480) and a biomass-based activated carbon (MSP700-A900CO2) is comparatively evaluated by combining experimental measurements and simulations. We examine the physicochemical properties of both materials, revealing that although WS-480 exhibits a higher of porosity, MSP700-A900CO2 contains a larger fraction of ultramicropores (<0.7 nm) and a broader distribution of oxygen-containing functional groups. These characteristics result in higher CO2 adsorption capacities for MSP700-A900CO2 in fixed-bed breakthrough experiments conducted under varying flow rates, temperatures and CO2 concentrations. We employ atomistic activated carbon models, augmented with surface functional groups as representations of WS-480 and MSP700-A900CO2, achieving close agreement with experimental adsorption data. The validated models are subsequently used to predict CO2/N2 separation under equilibrium and dynamic conditions, reproducing the experimental breakthrough behavior while providing molecular-level insight into the influence of pore structure and surface chemistry on adsorption performance.

cond-mat.mtrl-sci↗

arXiv2026

Evaluating Blended Refrigerants for Thermochemical Energy Storage and Circular Refrigerant Recovery using Activated Carbons

The climate crisis demands a rapid shift to sustainable energy technologies and higher efficiency in existing energy systems. Adsorption-based thermochemical energy storage is a promising alternative due to its high energy density and compatibility with renewable heat sources. In this work, we investigate the adsorption behavior of pure refrigerants (R32, R125, R134a, and R600) and their commercial blends (R410A, R407F, R417A, and R417C) in six activated carbons for thermochemical energy storage and circular refrigerant recovery. A multiscale computational workflow combining Monte Carlo simulations, thermodynamic modeling, and breakthrough simulations is developed to predict adsorption, storage, and separation behavior from pure-component adsorption data. The methodology integrates adsorption potential theory (APT), ideal adsorbed solution theory (IAST), and models for the isosteric heat of adsorption. In addition, an in-house computational framework is developed to calculate heats of adsorption and energy storage densities for both pure refrigerants and multicomponent mixtures. Although developed using molecular simulations as a benchmark, the methodology is directly applicable to experimental studies, since it only requires adsorption isotherms of the pure components as input to evaluate the performance of refrigerant blends. The results show that refrigerant blends can achieve higher storage densities than their pure counterparts due to cooperative adsorption and more efficient molecular packing. Furthermore, the activated carbons selectively separate key refrigerant components, highlighting their potential for sustainable refrigerant recovery. Overall, this work provides a general framework for the rational design and screening of next-generation refrigerant blends for adsorption-driven energy storage and separation applications.

cond-mat.mtrl-sci↗

arXiv2025

Enhancing Direct Air Capture through Potassium Carbonate Doping of Activated Carbons

Direct air capture of carbon dioxide (CO$_2$) is one of the most promising strategies to mitigate rising atmospheric CO$_2$ levels. Among various techniques, adsorption using porous materials is a viable method for extracting CO$_2$ from air, even under humid conditions. However, identifying optimal adsorbent materials remains a significant challenge. Moreover, the performance of existing materials can be improved by doping with active species that boost gas capture, a relatively unexplored field. In this study, we perform atomistic simulations to investigate the adsorption, structural, and energetic properties of CO$_2$ and water in realistic models of activated carbons. We first analyze the impact of explicitly considering surfaces containing functional groups, which aims to imitate the chemical environment of experimental samples. Additionally, we introduce potassium carbonate within the pores of the adsorbent to evaluate its effect on CO$_2$ and water adsorption. Our results demonstrate that both functional groups and potassium carbonate enhance adsorption, primarily by shifting the adsorption onset pressures to lower values. Specifically, potassium carbonate clusters act as extra adsorption sites for CO$_2$ and water, facilitating the nucleation of water molecules and promoting the formation of a hydrogen bond network within the activated carbon pores.

cond-mat.mtrl-sci↗

arXiv2024

Understanding the Role of Open Metal Sites in MOFs for the Efficient Separation of Benzene/Cyclohexane Mixtures

Separating C6 cyclic hydrocarbons, specifically benzene and cyclohexane, presents a significant industrial challenge due to their similar physicochemical properties. We conducted Monte Carlo simulations in the Grand-Canonical ensemble to acquire adsorption properties and separation performance data for benzene and cyclohexane in three metal-organic frameworks featuring coordinatively unsaturated metal sites (Ni-MOF-74, Ni-ClBBTA, and Ni-ClBTDD). The separation performance of these MOFs was analyzed and compared with literature data for adsorbents of different natures, demonstrating superior performance. Additionally, we explored the molecular origins of this effective separation, examining the pore-filling mechanism, interaction of guest molecules with metal centers, and mutual interactions of each adsorbate. Our results highlight that the selected adsorbents, with remarkable loading capacity, can efficiently separate both compounds in a mixture with exceptional effectiveness.

cond-mat.mtrl-sci↗

arXiv2023

Adapted Thermodynamical Model for the Prediction of Adsorption in Nanoporous Materials

In this paper, we introduce a novel, adapted approach for computing gas adsorption properties in porous materials. We analyze the Dubinin-Polanyi's adsorption model and investigate various frameworks to estimate its required essential components. Those are linked to physicochemical properties of the adsorbates, such as the vapor saturation pressure and density in the adsorbed state. To conduct this analysis, we obtain adsorption isotherms for several metal-organic frameworks, encompassing a range of pore sizes, shapes, and chemical compositions. We then apply and evaluate multiple combinations of models for saturation pressure and density. After the evaluation of the method, we propose a working thermodynamic model for computing adsorption isotherms, which entails using the critical isochore as an approximation of the saturation pressure above the critical point and applying Hauer's method with a universal thermal expansion coefficient for density in the adsorbed state. This framework is applicable not only to simulated isotherms but also to experimental data from the literature for various molecules and structures, demonstrating robust predictive capabilities and high transferability. Our method showcases superior performance in terms of accuracy, generalizability, and simplicity compared to existing methods currently in use. For the first time, a method starting from a single adsorption curve and based on physically interpretable parameters can predict adsorption properties across a wide range of operating conditions.

cond-mat.mtrl-sci↗

arXiv2023

Alcohol-Based Adsorption Heat Pumps using Hydrophobic Metal-Organic Frameworks

The building climate industry and its influence on energy consumption have consequences on the environment due to the emission of greenhouse gasses. Improving the efficiency of this sector is essential to reduce the effect on climate change. In recent years, the interest in porous materials in applications such as heat pumps has increased for their promising potential. To assess the performance of adsorption heat pumps and cooling systems, here we discuss a multistep approach based on the processing of adsorption data combined with a thermodynamic model. The process provides properties of interest, such as the coefficient of performance, the working capacity, the specific heat or cooling effect, or the released heat upon adsorption and desorption cycles, and it also has the advantage of identifying the optimal conditions for each adsorbent-fluid pair. To test this method, we select several metal-organic frameworks that differ in topology, chemical composition, and pore size, which we validate with available experiments. Adsorption equilibrium curves were calculated using molecular simulations to describe the adsorption mechanisms of methanol and ethanol as working fluids in the selected adsorbents. Then, using a thermodynamic model we calculate the energetic properties combined with iterative algorithms that simultaneously vary all the required working conditions. We discuss the strong influence of operating temperatures on the performance of heat pump devices. Our findings point to the highly hydrophobic metal azolate framework MAF-6 as a very good candidate for heating and cooling applications for its high working capacity and excellent energy efficiency.

physics.app-ph↗

arXiv2023

Adsorption Characteristics of Refrigerants for Thermochemical Energy Storage in Metal-Organic Frameworks

The adsorption of fluorocarbons has gained significant importance as its use as refrigerants in energy storage applications. In this context, the adsorption behavior of two low global warming potential refrigerants, R125 fluorocarbon and its hydrocarbon analog, R170, within four nanoporous materials, namely MIL-101, Cu-BTC, ZIF-8, and UiO-66 has been investigated. By analyzing the validity of our models against experimental observations, we ensure the reliability of our molecular simulations. Our analysis encompasses a range of crucial parameters, including adsorption isotherms, enthalpy of adsorption, and energy storage densities, all under varying operating conditions.We find remarkable agreement between computed and observed adsorption isotherms for R125 within MIL-101. However, to obtain similar success for the rest of the adsorbents, we need to take into account a few considerations, such as the presence of inaccessible cages in Cu-BTC, the flexibility of ZIF-8, or the defects in UiO-66. Transitioning to energy storage properties, we investigated various scenarios, including processes with varying adsorption and desorption conditions. Our findings underscore the dominance of MIL-101 in terms of storage densities, with R125 exhibiting superior affinity over R170. Complex mechanisms governed by changes in pressure, temperature, and desorption behavior make for complicated patterns, demanding a case-specific approach. In summary, this study navigates the complex landscape of refrigerant adsorption in diverse nanoporous materials. It highlights the significance of operating conditions, model selection, and refrigerant and adsorbent choices for energy storage applications.

cond-mat.mtrl-sci↗

arXiv2021

Efficient Computation of Metal Halide Perovskites Properties using the Extended Density Functional Tight Binding: GFN1-xTB Method

In recent years, metal halide perovskites (MHPs) for optoelectronic applications have attracted the attention of the scientific community due to their outstanding performance. The fundamental understanding of their physicochemical features is essential for improving their efficiency and stability. Atomistic and molecular simulations have played an essential role in the description of the optoelectronic properties and dynamical behaviour of MHPs, respectively. However, the complex interplay of the dynamical and optoelectronic properties in MHPs requires the simultaneous modelling of electrons and ions in relatively large systems, which entails a high computational cost, sometimes not affordable by the standard quantum mechanics methods, such as Density Functional Theory (DFT). Here, we explore the suitability of the recently developed Density Functional Tight Binding (DFTB) method, GFN1-xTB, for simulating MHPs with the aim of exploring an efficient alternative to DFT. The performance of GFN1-xTB for computing structural, vibrational and optoelectronic properties of several MHPs is benchmarked against experiments and DFT calculations. In general, this method produces accurate predictions for many of the properties of the studied MHPs, which are comparable to DFT and experiments. However, we also identify a few shortcomings, related to specific geometries and chemical compositions. Nevertheless, we believe that the tunability of GFN1-xTB is the key to resolving any observed issues and we propose specific targets, whose refinement will turn this method into a powerful computational tool for the study of MHPs and beyond.

cond-mat.mtrl-sci↗