Publisher：Colloids and Surfaces A: Physicochemical and Engineering Aspects  

Metal-organic frameworks (MOFs) are crystalline materials composed of metal ions and organic ligands, exhibiting distinctive physicochemical properties, including a large surface area, adjustable porosity, and malleability. These properties render MOFs superior to traditional porous matrices, particularly in adsorption and separation applications. In the present study, four metal ions (Mg²⁺, Co²⁺, Ni²⁺, and excess Ca²⁺) were directly integrated into the HKUST-1 structure to enhance its CO₂ adsorption capacity. Incorporating the four metals in excess resulted in a notable increase in the specific surface area and pore volume of N₂ adsorption compared to the pristine HKUST-1. Samples with larger specific surface area and pore volume exhibited enhanced CO₂ adsorption performance, indicating that doping excess metals introduces additional adsorption active sites. Notably, the combination of multiple analytical techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR), demonstrates that the modified sample exhibits enhanced crystallinity compared to the parent sample. The grain morphology remains unaltered, and no new chemical structures have been generated. Gold is present in the structure, albeit in trace amounts. Thus, the increase in active sites is due to competition between copper in the structure, the introduced excess doped metal coordination, and the generation of defects. Among the samples tested, Ca-HKUST-1 has demonstrated the most notable advancement, exhibiting an unprecedented three-fold increase in CO₂ absorption capacity compared to the original MOF. The synthesis process of this material is straightforward and cost-effective, rendering it highly suitable for industrial applications.

DOI： 10.1016/j.colsurfa.2024.135179

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Publisher：International Communications in Heat and Mass Transfer  

Adsorption heat pumps (AHPs) have been envisioned to be the next generation of cooling systems owing to their low electricity consumption and negligible total equivalent warming impact (TEWI). This study investigated the adsorption characteristics, thermodynamic properties, and environmental impact of HFC32 onto six waste mangrove-derived activated carbons (MACs), which were synthesized at various operating conditions. Adsorption isotherms were acquired below and above critical temperatures (30, 50, 70, and 90 °C) by a high-precision thermogravimetric analyzer (TGA). Notably, the most promising sample exhibited a remarkable HFC32 adsorption capacity (2.628 kgref per kgads), which is a benchmark for any HFC/AC pair to date. Six sets of isotherm data were fitted with well-established Dubinin-Astakhov (D–A) and Tóth equations, resulting in a notably high goodness of fit. The isosteric heat of adsorptions was also assessed and elucidated using the ideal Clausius-Clapeyron model and modified non-ideal models proposed by Rahman et al. and Chakrabarty et al. Furthermore, a comprehensive thermodynamic and ecological footprint analysis, including the specific cooling effect (SCE), coefficient of performance (COP), Clapeyron analysis, and total equivalent warming impact (TEWI) assessment, were conducted. The implementation of the aforementioned MAC/HFC pair can potentially achieve an SCE of 457 kJ kgads–1 for space cooling and approximately 25% reduction in CO2 emissions. Adsorption uptake, SCE, COP, and TEWI analyses collectively emphasize the significant potential of pairing MACs with HFC32 in designing an environmentally sustainable AHP.

DOI： 10.1016/j.icheatmasstransfer.2024.107828

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Publisher：International Communications in Heat and Mass Transfer  

This study experimentally and numerically investigated CO2 adsorption characteristics onto a highly porous activated carbon. Adsorption kinetics and isotherms experiments were conducted using a high-precision thermogravimetric analyzer. The effects of key parameters, specifically adsorbent bed thickness, temperatures, and pressure, were considered. The two isotherm models were employed to correlate the measured data, and they showed a decent fit. Numerical simulations were carried out using COMSOL Multiphysics software under a coupled heat and mass transfer model. The simulated results showed a reasonable agreement with the experimental uptakes for all studied parameters. The results also showed that the diffusion time constant Ds0/Rp2 is pressure-dependent and varies with the adsorbent bed thickness. The Ds0/Rp2 at each adsorption temperature is calculated and fitted with the Arrhenius equation. Estimated averaged values of limiting Ds0/Rp2 for adsorbent bed thicknesses of 0.9, 5, and 25 mm, respectively, equal to 2.18 × 10−1, 8.64 × 10−2, and 2.05 × 10−2 1/s. Linearly increasing adsorbent bed thickness causes a rapid nonlinear drop in Ds0/Rp2. The findings from this research provide valuable information on the mass transfer characteristics of CO2 onto activated carbon. So, engineers can design optimized heating/cooling systems that operate more effectively, resulting in higher efficiency, reduced system costs, and lower carbon emissions.

DOI： 10.1016/j.icheatmasstransfer.2024.107779

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Publisher：Technologies  

This study utilizes waste Albizia lebbeck wood from a sawmill to prepare activated carbon adsorbents and explores their potential application in adsorption cooling systems with a novel hydrofluoroolefin (HFO) refrigerant characterized by a low global warming potential. Activated carbon was synthesized through a simple and green steam activation method, and the optimal carbon shows a specific surface area of 946.8 m2/g and a pore volume of 0.843 cm3/g. The adsorption isotherms of HFO-1234ze(E) (Trans-1,3,3,3-tetrafluoropropene) on the activated carbon were examined at 30, 40, and 50 °C up to 400 kPa using a customized constant-volume variable-pressure system, and significant adsorption of 1.041 kg kg−1 was achieved at 30 °C and 400 kPa. The experimental data were fitted using both the Dubinin–Astakhov and Tóth models, and both models provided excellent fit results. The D–A adsorption model simulated the net adsorption capacity at possible operating temperatures. The isosteric of adsorption was determined using the Clausius–Clapeyron and modified Dubinin–Astakhov equations. In addition, the specific cooling effect and coefficient of performance were also studied.

DOI： 10.3390/technologies12070104

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Publisher：Thermal Science and Engineering Progress  

Metal-organic framework (MOF), an advanced category of porous coordination polymers, has recently gained prominence as a novel class of adsorbent materials, captivating the attention of researchers worldwide engaged in diverse applications related to adsorption. An adsorption heat lifter or adsorption heat transformer (AdHT) plays a crucial role in elevating the temperature of a waste heat source. This is achieved by harnessing the adsorption enthalpy or isosteric heat of adsorption. The system performance of the AdHT system is affected by the working pairs, which leads to a possible application for MOF/water working pairs in such a system. In this study, 2-tank and 3-tank systems are invoked to investigate and compare the coefficient of performances (COPs) of three MOFs: MOF–801, aluminum fumarate, and MIL–100(Fe) paired with water while considering an atmospheric temperature of 308.15 K. With a waste heat source and cooling water temperature difference (T<inf>D</inf>) of 70 K in the 3-tank system, MOF–801/water outperforms aluminum fumarate and MIL-100(Fe). Considering a temperature driving force that explains the temperature change of heat transfer fluid during the flowing procedure inside pipes, ΔT = 5 K, the MOF–801/water pair can provide a gross temperature lift of around 30 K at a relatively good COP of 0.4867. There are very few articles that studied the MOFs/water pair for AdHT 2-tank and 3-tank system applications. Hence, the results of this study highlight their viability for designing environmentally friendly and energy-efficient heating systems.

DOI： 10.1016/j.tsep.2024.102595

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Publisher：International Communications in Heat and Mass Transfer  

Adsorption Cooling Systems ADCS as a thermally-driven technology provide an environmentally benign solution to supply cooling needs and utilize low-temperature heat sources. Adsorbent materials are the key element in the cooling performance of the ADCS. Poor heat transfer and low packing density are the main drawbacks of the conventional adsorbents, such as silica gel, that hinder the ADCS performance. Consolidated composite adsorbents represent a great solution for this problem, in which the binder material plays a significant role in the composite adsorbent synthesis and performance. In this paper, composite adsorbent based on RD Silica Gel SG as parent material and amino acid-based Polymerized Ionic Liquid PIL as a binder material, is synthesized at different PIL percentages, namely 2%, 5%, and 10%. The thermal and adsorption characteristics of the developed composite adsorbents in addition to the theoretical cooling performance ADCS with water adsorbate have been investigated. The results show that the thermal diffusivity has been improved by a maximum value of 20% for Composite 3, while the average volumetric water uptake has been enhanced for Composite 1 by a maximum value of 20.6%, compared to the parent silica gel.

DOI： 10.1016/j.icheatmasstransfer.2023.106862

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Solar Energy  

This study presents a theoretical thermoeconomic performance assessment of a novel solar-powered high-temperature heat pump (HTHP)/adsorption cogeneration system for simultaneous electricity production and cooling. Photovoltaic/thermal (PVT) solar collectors are used to capture solar thermal energy and generate electricity that is partially used to drive the HTHP compressor. The HTHP is mainly used to absorb the captured solar thermal energy through its evaporator coils to keep the collectors at lower operating temperatures for better electricity generation. Then through the HTHP compressor, the thermal energy is amplified to produce higher-temperature hot water to drive the adsorption chiller for improved cooling production. The performance of the proposed system (PVT-HTHP) is compared to the performance of the PVT-only, and evacuated tube collectors (ETC-only) powered adsorption chiller for the same solar collector area. A parametric study with different operating HTHP conditions has been performed to determine the optimal operational scenario for the proposed system. A low-GWP refrigerant R1234ze(Z) is considered for the HTHP and compared against the conventional high-GWP R134a option. A complete dynamic mathematical model is developed for the studied systems and solved by MATLAB software. Under the summer conditions of Alexandria, Egypt, the average cooling capacity is improved substantially from 3.91 kW for PVT-only to 8.6 kW for ETC-only and 10.21 kW for proposed PVT-HTHP configuration with R1234ze(Z) and operating evaporator and condenser temperatures of 35 °C and 90 °C, respectively. The best-performing configuration from the energy efficiency perspective is the proposed PVT-HTHP with R1234ze(Z) refrigerant at a value of 46.8% when the operating HTHP evaporator and condenser saturation temperatures of 35 °C and 80 °C, respectively. The economic assessment of the proposed PVT-HTHP system proves that the system can be applied feasibly with a payback period (PBP) of 7.5 years.

DOI： 10.1016/j.solener.2023.03.017

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Other Link： https://doi.org/10.1016/j.solener.2023.03.017

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of The Institution of Engineers (India): Series C  

Nearly two billion air-conditioning (AC) units are currently being used for space cooling worldwide. The majority of these ACs use R134a as the working fluid, a greenhouse gas (GHG) with a global warming potential (GWP) of 1300 kg-CO2-eq. According to the rules set by the world environment safety organizations, the GWP of domestic air-conditioning systems must not exceed 750 kg-CO2-eq. Hence, the R134a must be phased out by 2025, and an alternative refrigerant with similar thermodynamic properties yet low GWP is required. Therefore, the authors have investigated several potential binary/ternary refrigerant blends in this study. Among the studied refrigerants, R445A, R30A, and NPB2 (newly proposed blend: 8% R152a + 92% R1234yf) can reduce 90–99% global warming impact (more than 200 million tonnes of CO2 emission equivalent) caused by the domestic air-conditioning systems every year.

DOI： 10.1007/s40032-023-00927-y

Scopus

Other Link： https://doi.org/10.1007/s40032-023-00927-y

Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Journal of Refrigeration  

HFOs are currently being adopted for adsorption refrigeration applications due to their zero ozone depletion potential and paltry global warming potential. In this study, a constant volume variable pressure (CVVP) system is designed and built to experimentally investigate the adsorption characteristics of HFO-1234ze(E) onto Maxsorb III. Experiments were performed to obtain refrigerant uptakes at adsorption temperatures of 30, 40, and 50°C at variable refrigerant pressures. The maximum experimental adsorption uptake is 1.73 kg·kg–1 at 0.607 relative pressure. The uptake starts to increase sharply from 0.01 relative pressure and slows down at 0.2 relative pressure. The experimental adsorption isotherm data were correlated with Tóth and Dubinin-Astakhov (D–A) adsorption isotherm models. Uptake difference based on Tóth and D–A adsorption model at possible working temperature has been simulated. Isosteric heats of adsorption were determined from Clausius–Clapeyron relation, and their dependence on uptake was also analyzed and reported. Additionally, the specific cooling effects and coefficient of performance are investigated. These findings are crucial for the system performance assessment of a practical adsorption refrigeration system.

DOI： 10.1016/j.ijrefrig.2022.11.005

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Other Link： https://doi.org/10.1016/j.ijrefrig.2022.11.005

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Thermal Science and Engineering Progress  

Metal-organic frameworks (MOFs) are inorganic–organic hybrid porous crystalline materials featured by exceptionally high surface area, tunable porosity, and controllable chemical structures, making them efficient candidates for gas adsorption. HKUST-1 is a promising MOF constructed from the coordination bonding of copper paddle-wheel metal nodes and 1,3,5-benzenetricarboxylates. In this study, HKUST-1 was synthesized according to a hydrothermal synthesis procedure, and two alkaline metal ions (Ca2+ and Mg2+) and two transitional metal ions (Co2+ and Zn2+) were individually doped in situ in the framework of HKUST-1. The synthesized pristine HKUST-1 and the metal-doped MM-HKUST-1 were then characterized experimentally. MM-HKUST-1 samples were isostructural with the pristine MOF, and larger surface area and increased pore volume were observed due to metal doping. The effect of the presence of different metals on the water sorption capacity was investigated by volumetric water sorption analysis. The incorporation of metal ions Co2+ and Mg2+ enhanced the affinity towards water vapor, whereas the equilibrium uptake capacity of the other two metal-doped samples was comparable with the parent one. The increased water uptake capacity eventually increased the SCE of the Co-HKUST-1 sample for providing cooling of 15 °C with heat source temperatures of 50 °C and 60 °C.

DOI： 10.1016/j.tsep.2022.101453

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Other Link： https://doi.org/10.1016/j.tsep.2022.101453

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Sustainable Materials and Technologies  

Adsorption-assisted energy conversion technologies are receiving extensive attention recently as a sustainable technology for meeting the worldwide energy demand. The advancement of this technology relies on the development of the mass and heat transfer properties of the adsorbent materials. MOF-801, a zirconium-based microporous metal organic framework (MOF), is regarded as a promising adsorbent for adsorption-assisted energy conversion technologies. This study focuses on enhancing the water sorption properties of MOF-801 by introducing different transitional metals, nickel, and cobalt, into the framework. Herein, two novel bimetallic MOFs were synthesized by partial substitution of the metal zirconium in MOF-801 with nickel and cobalt, employing a one-pot solvothermal synthesis method. The bimetallic MOFs, Ni-MOF-801, and Co-MOF-801, were found isostructural with the pristine MOF-801. Porous properties were measured experimentally, and an increment in total surface area and microporous surface area was observed for both samples. The water adsorption isotherm of the samples was measured, and a greater affinity at the lower pressure region was observed compared to the pristine MOF due to the synergistic effects of two metals in the frameworks. This greater affinity towards water vapor resulted in an increase in effective net uptake and specific cooling effect. The thermophysical properties were measured experimentally over a wide range of temperatures, and an improvement was found in the doped MOF-801 samples. Co-MOF-801 outperformed the pristine MOF-801 with a 43% improvement in specific cooling effect for delivering high-grade cooling at 10 °C with the same working conditions. The results will significantly contribute towards the development of high-performance next generation adsorption-based energy conversion systems.

DOI： 10.1016/j.susmat.2022.e00442

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Other Link： https://doi.org/10.1016/j.susmat.2022.e00442

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Applied Thermal Engineering  

To further the research on R32 refrigerant-based adsorption cooling applications, Maxsorb-III activated carbon composites synthesized with the additives of H25 Graphene nanoplatelets (GNP), 1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide ([HMIM][Tf2N]) ionic liquid with polyvinyl alcohol (PVA) are studied for cooling performance evaluation. Their respective kinetic characteristics and heat of adsorption assessments are carried out for this purpose in the present study. The adsorption kinetics characteristics are studied using gravimetrically for the composite samples. A first-order kinetics model is seen to fit their kinetic uptakes with regression coefficients ≥ 0.97. The heat of adsorption estimates of the composites for varying uptakes and temperatures are numerically evaluated, incorporating the non-ideal behavior of the refrigerant. An approach for a holistic comparison of the cooling performances of the composites containing their respective heat and mass transfer characteristics for compact heat exchanger designs is further proposed. While the composite with the highest Maxsorb-III mass fraction yields the highest specific and volumetric cooling powers, the composite with the highest thermal conductivity requires the lowest heat exchanger area with a slightly larger adsorbent volume of around 12.1% over the former. A second law thermodynamic analysis is further carried out to evaluate the composite performances for cooling applications.

DOI： 10.1016/j.applthermaleng.2022.118359

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Other Link： https://doi.org/10.1016/j.applthermaleng.2022.118359

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Bulletin of the Chemical Society of Japan  

Current greenhouse gas emissions suggest that keeping global temperature increase below 1.5 degrees, as espoused in the Paris Agreements will be challenging, and to do so, the achievement of carbon neutrality is of utmost importance. It is also clear that no single solution can meet the carbon neutral challenge, so it is essential for scientific research to cover a broad range of technologies and initiatives which will enable the realization of a carbon free energy system. This study details the broad, yet targeted research themes being pioneered within the International Institute for Carbon-Neutral Energy Research (I2CNER). These approaches include hydrogen materials, bio-mimetic catalysts, electrochemistry, thermal energy and absorption, carbon capture, storage and management and refrigerants. Here we outline the state of the art for this suite of technologies and detail how their deployment, alongside prudent energy policy implementation can engender a carbon neutral Japan by 2050. Recognizing that just as no single technological solution will engender carbon neutrality, no single nation can expect to achieve this goal alone. This study represents a recognition of conducive international policy agendas and is representative of interdisciplinary, international collaboration.

DOI： 10.1246/bcsj.20210323

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Other Link： https://doi.org/10.1246/bcsj.20210323

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijrefrig.2021.08.014

Other Link： https://doi.org/10.1016/j.ijrefrig.2021.08.014

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Heat Transfer Engineering  

Activated carbon signifies extensive carbonized materials of a high degree of porosity and has a wide range of applications. The porous and thermal properties of activated carbon (AC) are primarily dependent on the chosen raw material and synthesis conditions. In this article, the thermophysical properties of twelve waste biomass-derived AC samples are investigated and correlated. These AC samples are synthesized from mangrove and waste palm trunk. The samples are different in terms of carbonization temperature (500 and 600°C), activation temperature (600 to 900°C), and the mixing ratio (4 or 6) of the activation chemical, which is potassium hydroxide. The specific heat capacity of W-AC-C600-A900-K6 is found to have the lowest (0.843 to 1.14 kJ kg−1 K−1), and M-AC-C500-A900-K4 shows the highest (1.18 to 1.86 kJ kg−1 K−1) among the studied samples. Experimental data are fitted with the Green-Perry model with an error of less than 2%. This study also accounts for the comparison of specific heat capacity of studied samples and other adsorbents such as AC obtained from different precursors, silica gels, carbon-based consolidated composites, and metal-organic frameworks found in the literature. Moreover, this study gives the insight to synthesize high-quality AC from unknown biomass sources for a particular application.

DOI： 10.1080/01457632.2021.2001743

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Other Link： https://doi.org/10.1080/01457632.2021.2001743

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Energy  

Solid-gas adsorption has drawn considerable attention utilizing low-grade waste heat and environment-friendly refrigerants for cooling, heating, and air-conditioning. However, low sorption capacity of the adsorbents is a long-standing challenge for achieving highly efficient adsorption heat pumps. This study aims to analyze and compare the performance of green synthesized transitional metal (10% Ni and 10% Co) doped aluminum fumarate metal-organic frameworks as adsorbent materials in an adsorption chiller where water is considered as the refrigerant. Water uptakes on these adsorbents were measured at 303 K, 323 K, and 343 K gravimetrically. It was found that both Ni and Co-doped samples showed higher equilibrium uptake when compared with the parent sample while the adsorption isotherm moved towards the lower pressure region. Additionally, adsorption cycles involving the pressure, temperature, and uptakes (P-T-q diagrams) were drawn to investigate their cyclic performances. The specific cooling effects were also calculated and compared among the associated adsorbent/adsorbate pairs having the adsorption, desorption, evaporator, and condenser temperatures considered as 303 K, 353 K, 288 K, and 308 K, respectively. Additional studies were conducted using the inverse gas chromatography technique to investigate the relation between the surface properties and the water adsorption isotherms.

DOI： 10.1016/j.energy.2021.122079

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Other Link： https://doi.org/10.1016/j.energy.2021.122079

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2021.121112

Other Link： https://doi.org/10.1016/j.ijheatmasstransfer.2021.121112

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/01457632.2020.1777005

Other Link： https://doi.org/10.1080/01457632.2020.1777005

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijrefrig.2020.12.032

Other Link： https://doi.org/10.1016/j.ijrefrig.2020.12.032

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.applthermaleng.2020.115361

Other Link： https://doi.org/10.1016/j.applthermaleng.2020.115361

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijrefrig.2019.10.027

Other Link： https://doi.org/10.1016/j.ijrefrig.2019.10.027

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.applthermaleng.2019.114431

Other Link： https://doi.org/10.1016/j.applthermaleng.2019.114431

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2019.118579

Other Link： https://doi.org/10.1016/j.ijheatmasstransfer.2019.118579

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2349301

Other Link： https://doi.org/10.5109/2349301

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5109/2321014

Other Link： https://doi.org/10.5109/2321014

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jced.7b00818

Other Link： https://doi.org/10.1021/acs.jced.7b00818

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.applthermaleng.2017.09.057

Other Link： https://doi.org/10.1016/j.applthermaleng.2017.09.057

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijhydene.2017.07.035

Other Link： https://doi.org/10.1016/j.ijhydene.2017.07.035

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.7567/JJAP.54.125701

Other Link： https://doi.org/10.7567/JJAP.54.125701