Rising CO2 emissions and environmental pollution entail the need to develop advanced utilizing renewable energy technologies. Adsorption Cooling (AC) is a novel energy saving and environmentally benign technology, which allows effective utilization of solar or waste heat. The efficiency of AC greatly depends on the properties of adsorbents used. Metal-organic framework NH2-MIL-125 is considered promising for AC due to its step-wise isotherms of water adsorption and large adsorption capacity. Less data is available on the details of water transport in NH2-MIL-125 pores, although it is a crucial parameter for evaluating key performance indexes of AC. Here, the kinetics of water adsorption on loose NH2-MIL-125 grains was measured using an Isothermal Differential Step method. The effects of grain size and water uptake are studied. The rate limiting stages are determined and the corresponding water diffusivities are calculated. The data obtained are essential for optimization of AC cycles and adsorber configuration.

With the rise of intensive computing, the power consumption of big data centers (BDCs) has increased significantly, with 40 % being spent on cooling. This requires the development of energy-efficient technologies for cooling BDC components. Adsorption Cooling (AC) is an environmentally friendly technology that can utilize BDC waste heat to cool their components. However, the ultra-low temperature level (45-60 degrees & Scy;) of this heat requires the search for new advanced adsorbents specialized for these harsh conditions, which is the aim of this study. Firstly, the demands for adsorbent sorption properties are formulated; the water adsorption equilibrium is compared for commercially available mesoporous silicas (pore sizes ranging from 2 to 8 nm) to select the most promising adsorbent for this cycle. At a heat rejection temperature of 30 degrees C, the mesoporous silica with 4.6 nm pores produces cold at T = 25 degrees C, sufficient for cooling BDC, with water uptake of 0.44-0.47 gH2O/gads, and can be regenerated at 50-60 degrees C. The main performance indexes of the cycle are assessed: the Coefficient of Performance of 0.86 and Specific Cooling Power of 0.7-3.1 kW/kg. This provides a solid foundation for the designing a compact energy-saving adsorption unit for waste heat recovery and BDCs cooling using this commercially available and cost-effective adsorbent.

Intensification of the adsorption dynamics is a strategic way to make adsorption chillers and heat pumps more competitive with conventional vapour compression systems. This can be achieved by consolidating the adsorbent bed with a heat exchanger to enhance heat transfer. This work investigates the dynamics of water adsorption on a commercial adsorbent SAPO-34 for three bed configurations, namely, a reference bed consisting of a monolayer of loose beads located on an aluminium plate, and two consolidated beds - a monolayer of beads glued to the plate, and a homogeneous coating of the plate prepared with binder. The morphology and texture of the prepared beds were studied by optical and scanning electron microscope techniques as well as by low temperature nitrogen adsorption. Six binders involved, both organic (hydroxyethyl cellulose, polyvinylpyrrolidone, polyaniline) and inorganic (heat-conductive compound CPTD, bentonite clay, colloidal silica sol), produced varying effects. It was found that the most preferred configuration involves SAPO beads glued to the plate with bentonite for which the heat transfer was enhanced by a factor of 1.2-1.7 while maintaining sufficient mass transfer. The effective heat transfer coefficient was measured for the most promising binders and selected configurations, and varied between 120 and 248 W/(m2 K). The heat transfer acceleration permitted the specific cooling power (at a conversion of 0.8) to increase from 2.7 kW/kg for loose beads of 0.8-0.9 mm size to 3.5 kW/kg for the same beads bound with bentonite. Thus, gluing pre-made commercial adsorbent beads with heat-exchanger with suitable binders presents a simple and promising method to enhance the adsorption dynamics, resulting in a more compact design of adsorption chillers.

Adsorption heat pumps are an alternative way of heat and cold generation. Due to the high adsorption capacity and high specific energy storage capacity, the SWS-1L adsorbent can be efficient in adsorption heat pumps. The physicochemical properties of various adsorbents and kinetics of adsorption and desorption of vapors of working fluids based on them have been studied quite well, and methods have been developed to optimize the efficiency of cycles with consideration of a large number of determining parameters: properties of adsorbent, temperature, pressure, and geometric parameters of the adsorbing heat exchanger. However, there is little experimental data on the change with time in the temperature of the free surface of a layer of adsorbent granules. It is important to know how this temperature varies for accurate calculation of the heat transfer parameters. The work shows that at the beginning of heating, the surface temperature of the heat exchanger (metal) without an adsorbent increases to a quasi-stable value within 40–45 s. In the presence of the adsorbent, this time almost doubles and corresponds to 70–75 s. Increase in the thermal fluid flow from 0.65 l/min to 2.7 l/min (4.1 times) leads to a 3.8-fold decrease in the heating time of the heat exchanger with the adsorbent (also approximately 4 times). The characteristic time of thermal inertia (along the thickness of the heat exchanger wall and along the height of the adsorbent layer) without and with the adsorbent is 0.5–1 s and 4–6 s, respectively. The growth of the thermal fluid velocity leads to a significant reduction in the heating time of the heat exchanger and adsorbent and can also reduce the desorption time in a heat pump.

The adsorption method for atmospheric water harvesting (AWH) is considered as a promising heat-driven technology for potable water supply in arid regions. This research is focused on novel composite sorbents based on hygroscopic salts loaded in the pores of MIL-101(Cr) developed for AWH. The composites based on LiCl, LiBr, CaCl2 , and Ca(NO3 )2 were synthesized and comprehensively studied by SEM, XRD, N2 adsorption, and thermogravimetric methods. We evidence that the CaCl2 /MIL-101(Cr) composite demonstrates a high net water uptake of 0.52-0.59 g_(H2 O)/g_(composite) per cycle under conditions of Saudi Arabia and the Sahara desert as the reference regions with extra-dry climate, which exceeds the appropriate values for other adsorbents. It is shown that water adsorption on the composite cannot be presented as a combination of the adsorption on the components, thus indicating a synergistic effect. A detailed characterization of water coordination, mobility, and hydrogen bonding within the confined CaCl2 hydrates and salt solution using solid-state 2 H NMR spectroscopy has been performed. It is established that pore confinement promotes a prolonged transition to a dynamically melted state of the hydrated salt and a notable decrease of the melting temperature, which facilitates the molecular transport of water and causes the alteration of sorption properties of CaCl2 inside MIL-101 pores. Finally, the performance of AWH employing CaCl2 /MIL-101(Cr) was evaluated in terms of the fractions of water extracted and collected, and the specific energy consumption, demonstrating its high potential for AWH.

Adsorption Heat Conversion (AHC) is energy and environment saving alternative to conventional compression systems. The growth of specific power of AHC systems is a prerequisite for the wider spreading of AHC. To enhance the power, an innovative adsorbent bed configuration was suggested, namely, a compact adsorbent layer prepared by gluing to heat exchanger surface ready-made grains instead of uniform adsorbent coating. The main goal was a comparative study of water sorption dynamics on loose and glued grains of a composite LiCl/ (silica gel) to evaluate the power enhancement. The grains were glued to aluminium foil with various binders, both organic and inorganic, the effect of the binder nature was studied. The effective heat transfer coefficient was evaluated under typical conditions of adsorption chilling cycle. The main findings are: (a) the effective heat transfer coefficient is increased up to 1.5 times when using inorganic binders; (b) organic binders do not affect heat transfer; (c) heat transfer intensification leads to accelerating initial stage of the ad/desorption; (d) at longer times, a desorption slowdown is observed due to hindered mass transfer or LiCl crystallisation. The factors controlling the adsorption kinetics are determined and recommendations are formulated for designing innovative bed configuration.

Adsorption thermal batteries have been proposed for storing heat from renewable and waste energy sources. Composites "salt in porous matrix" based on expanded vermiculite have extraordinary methanol sorption and heat storage capacities. However, their practical implementation is restricted by slow desorption, leading to low battery power. This paper aims to accelerate methanol desorption from a composite LiCl/vermiculite through its modification by an aluminum-oxygen containing additive. First, the dynamics of methanol sorption/desorption is studied for a pristine LiCl/vermiculite to reveal the factors braking sorption. Slow heterogeneous nucleation and sluggish growth of crystalline LiCl are shown to dramatically inhibit the methanol desorption from the pristine LiCl/vermiculite composite. To accelerate the nucleation, the vermiculite is modified by 2.5-8.9 wt% of aluminum-oxygen containing additive. Both pristine and modified sorbents are characterized by XRD, SEM, DSC, and BET techniques. The modification allows a giant acceleration of methanol desorption. The characteristic time corresponding to conversion 0.8 reduces by a factor of 2-12 as compared with the pristine composite. The dy-namics acceleration affords fourfold increase in the specific power of the heat storage stage of adsorption thermal batteries employing the new composite. In a broader sense, the proposed approach could help accelerate the sorption of methanol, water, and ammonia on composites based on macroporous matrixes and could be ad-vantageous for various adsorption applications.

In this work, we investigated the state of water in the metal-organic framework MIL-101(Cr) by combining H-1 magic angle spinning (MAS) NMR, NMR relaxometry, and molecular dynamics (MD) simulations based on a reactive force field. The MD simulations indicated that water molecules are coordinated to the open metal sites and are organized in shells. Through H-1 T-2 and T-1 relaxation measurements at the fixed Larmor frequency of 21 MHz, water in the intergrain spaces was distinguished from that in the intragrain mesopores of MIL-101(Cr). H-1 MAS NMR measurements showed that water in the mesopores is structurally ordered, as revealed by the presence of H-1-H-1 residual dipolar interaction. The H-1 NMR relaxometric behavior of water located in the intergrain spaces of MIL-101(Cr) as a function of the magnetic field strength, determined by fast field cycling NMR relaxometry, was interpreted extending an existing model, generally applied to paramagnetic aqua ions in solution, to the case of Cr3+ ions fixed on the surface of the metal-organic framework. The model predicts the exchange of water between the first and second shell of a Cr3+ ion, giving access to the water residence time in the first shell that would be difficult to determine using other techniques. In the temperature interval of 25-70 degrees C, water residence times in the range of tens of nanoseconds were found and a limited accessibility of water to the open metal sites located on the external grain surface was observed.

Adsorption heat transformation and storage (AHTS) is an environmentally benign and energy-saving alternative to common compression chillers and heat pumps. The low specific power (SP) of adsorption systems is a key drawback that hinders their broader dissemination. The optimization of adsorption dynamics is a prerequisite for SP enhancement. In this work, we studied the dynamics of water vapor adsorption on MOF-801—a promising adsorbent for AHTS. For the first time, two configurations of compact MOF-801 bed, namely, grains glued to the surface of a metal support and thin adsorbent coatings, are prepared, and their porous structure is characterized. The water adsorption dynamics is compared with a common loose grains configuration. The main findings are: (a) the binder can both accelerate and decelerate the water adsorption, and its chemical nature is subject to careful selection; (b) at the initial time, heat transfer between the support and adsorbent bed controls the adsorption rate, and, at a longer time, mass transfer starts to affect it; (c) polyvinylpyrrolidone, bentonite, thermal grease, and hydroxyethylcellulose increase the heat transfer coefficients and accelerate adsorption; polyvinyl alcohol and polyaniline slow it down; and (d) for the coatings prepared with polyvinylpyrrolidone, an SP of 1.6–5.1 kW/kg can be achieved, which is about twice that for the loose grains. The new configurations can be recommended for effective but expensive adsorbents such as MOFs, and their implementation will contribute to the further spread of AHTS technology.

Due to the rapidly growing population, industry, and agriculture, the potable water shortage is becoming one of the global challenges of our time. Simultaneously, the atmosphere contains 12,900 km3 of moisture available everywhere, regardless of geographical location and climatic conditions. In this context, the technology of Adsorptive Water Harvesting from the atmosphere (AWHA) is considered a promising method for decentralized water supply for domestic and sanitarian purposes in arid regions. The AWHA is based on the reversible sorption of water vapor on a desiccant and heat-powered desorption of the stored water with its subsequent condensation. The sorbent is a key element of AWHA, and its properties strongly affect the system’s performance. New opportunities for AWHA might open up with the development of novel adsorbents with advanced properties. In this chapter, first, the principle and basic technical solutions of AWHA are described and the properties of the sorbent required are outlined. Then the new classes of advanced sorbents suggested for AWHA are reviewed with a special focus on Metal–Organic Frameworks and the composite sorbents based on a hygroscopic salt embedded inside a matrix, the properties of which can be tuned according to the climatic conditions of a specific region, where the process is realized. Finally, the advantages and challenges of these adsorbents are discussed and some prospects on the adsorbents promising for continuously operating and scalable AWHA systems are provided.

Adsorption processes are widely used to convert heat with low- or even ultralow-temperature (ULT) potential. For instance, the adsorptive VentireG process was proposed to regenerate ULT heat and moisture in ventilation systems in cold countries. In this paper, a new approach for a deeper analysis of this process is proposed. It is implemented by plotting water adsorption isosters for a specific adsorbent directly on the common psychrometric chart of humid air. Such a combined diagram would allow the states of air and the given adsorbent to be tracked simultaneously. The merged "psychrometric - isosteric" diagram is plotted for five adsorbents potentially promising for the VentireG process. Their possible application in typical climatic zones of cold countries is analyzed, and the conscious choice of proper adsorbents is made. Composites "salt (CaCl2, LiCl, LiBr) in silica pores" can exchange up to 0.4-0.5 g_H2O/g and ensure low dew point of the outlet air. In a broader sense, this new combined diagram can be used for analyzing any open adsorption cycles, e.g., for air conditioning, desiccation, water harvesting from the atmosphere, etc. (C) 2021 Elsevier Ltd. All rights reserved.

Обобщены актуальные направления исследований в области металл-органических координационных полимеров (МОКП), проводимых в научных организациях и университетах России в последние 5—10 лет. Обзор охватывает вопросы дизайна, синтеза, топологического описания и прогнозирования свойств МОКП, разработки способов их химического конструирования и модификации, изучения современными физико-химическими методами, создания функциональных материалов на основе пористых каркасов (гетерогенных катализаторов, высокоэффективных и высокоселективных сорбентов нового поколения, проводящих материалов, систем для адресной доставки лекарств).

Sorption systems for thermal energy storage (STES) have aroused an increasing interest as a promising way for efficient utilization of low-grade energy sources, such as solar or waste heat of domestic, transportation and industry sectors. In this chapter, we describe the basic principles of closed sorption heat storage, presenting several popular working cycles on a thermodynamic diagram. Then, the basic classes of the sorbents for STES in closed sorption systems are critically and briefly reviewed. Finally, the main results of the prototypes testing are presented.

Current research fields of metal-organic frameworks (MOFs), which are being developed in the last 5-10 years by Russian scientific institutions and universities, are generalized. The review encompasses the design, synthesis, topological description, and prediction of MOF properties, the development of methods for their chemical engineering and modification, their investigation by modern physicochemical techniques, and the creation of functional materials based on porous frameworks (heterogeneous catalysts, highly efficient and highly selective sorbents of the new generation, conducting materials, systems for the target drug delivery).

According to the BP Statistical Review of World Energy 2020 [...]

The influence of adsorbed water on the dynamics of the organic linker 1,4-benzenedicarboxylate (BDC) in the metal organic framework NH2-MIL-125 was examined by applying C-13 Nuclear Magnetic Resonance (NMR) spectroscopy on samples loaded with different amounts of water. In particular, the analysis of (i) cross-polarization (CP) C-13 Magic Angle Spinning (MAS) NMR spectra in terms of chemical shift and line width of the carbon signals, (ii) variable contact time C-13 CP-MAS experiments, and (iii) longitudinal C-13 relaxation times indicated that, upon hydration, a dynamic process occurring on the microseconds timescale accelerates. This process could be identified with the rotation of the BDC benzene ring about its C-2 axis, with water competing with the carboxylic oxygen for hydrogen bonding with the aminic group. Other motions occurring at frequencies on the order of the C-13 Larmor frequency, i.e. 75 MHz, which contribute to the flexibility of the three-dimensional network, were detected, and identified with the twisting, libration and translation of the BDC linker.

In recent years, growing energy demands and environmental pollution caused by the extensive use of fossil fuels have inspired considerable research interest in adsorptive heat transformation (AHT). This technology offers effective utilization of low-grade solar or waste thermal energy for cooling and heating with low environmental impact. Increasing the AHT power is a keystone for further development and dissemination of this emerging technology. The AHT power is mainly determined by ad/desorption dynamics, which is significantly hindered by slow heat transfer between the adsorbent and heat exchanger. Shaping the adsorbent bed as a coating on the heat exchanger surface is considered an effective route to enhance heat transfer and increase the AHT power. In this review, the technology of adsorbent coating for AHT is comprehensively surveyed, including coating synthesis, adsorption dynamics, and use in real AHT devices. The advantages of the coated bed configuration are considered, and its challenges are outlined. Finally, recommendations for better organization of the coating’s structure for rational control of the relative contributions of heat and mass transfer are considered.

Adsorption technologies for Heat Conversion (AHC) and Water Harvesting (AWH) hold great potential for energy management because they can utilize renewable energy or low-grade heat resources. A keystone for the successful implementation of these technologies is the properties of the adsorbent. Metal-organic frameworks (MOFs) show tremendous promise for these applications, owing to their high adsorption capacity and the possibility of target-specific design. However, there are several challenges to be solved, namely, low hydrothermal stability of MOFs, high cost, and complicated synthesis. The further progress of these technologies depends on the inter-disciplinary research in Applied Thermal Engineering (ATE) and Materials Science (MS) and close collaboration between these two scientific societies is required. In this review, we try to bridge the gap between ATE and MS scientists. To this purpose, the principles of AHC and AWH are described, the specific features of adsorbents needed for AHC and AWH are defined, and promising MOFs are considered. MOFs fabrication strategies and long-term reliability are viewed. Finally, we provide some perspectives on advanced MOFs promising for continuously-operating and scalable AHC and AWH systems.