Evaluation of ZIF-8 and ZIF-90 as Heat Storage Materials by Using Water, Methanol and Ethanol as Working Fluids

Abstract

The increasing demand for heating/cooling is of grave concern due to the ever-increasing population. One method that addresses this issue and uses renewable energy is Thermochemical Energy Storage (TCES), which is based on the reversible chemical reactions and/or sorption processes of gases in solids or liquids. Zeolitic imidazolate frameworks (ZIFs), composed of transition metal ions (Zn, Co, etc.) and imidazolate linkers, have gained significant interest recently as porous adsorbents in low temperature sorption-based TES (sun/waste heat). In this study, we examined two different sodalite-type ZIF structures (ZIF-8 and ZIF-90) for their potential heat storage applications, based on the adsorption of water, methanol and ethanol as adsorbates. Both ZIF structures were analysed using PXRD, TGA, SEM and N2 physisorption while the % adsorbate uptake and desorption enthalpy was evaluated using TGA and DSC analysis, respectively. Among the studied adsorbent–adsorbate pairs, ZIF-90-water showed the highest desorption enthalpy, the fastest sorption kinetics and, therefore, the best potential for use in heat storage/reallocation applications. This was due to its significantly smaller particle size and higher specific surface area, and the presence of mesoporosity as well as polar groups in ZIF-90 when compared to ZIF-8.

Molecular and Artificial Neural Networks Modeling of Sorption and Diffusion of Small Alkanes, Alkenes and Their Ternary Mixtures in ZIF-8 at Different Temperatures

“…In addition, ANN predictions at 300 K and the same pressure give S ethane,ethene ANN (10 bar) = 2.7 and S ethane,methane ANN (10 bar) = 10.9. The highest selectivities monitored for ethane over methane and for ethane over ethene were close to 17 and 3.2, respectively, for pressures in the [2,10] bar window and at 273 K. The GCMC and ANN results reveal a significant sorption selectivity of ethane over ethene and methane in ZIF-8 which can achieved in a range of pressures and for different temperatures above and below the room temperature.…”

“…The first molecules with carbon−carbon bonds, which include ethane and ethene are also shown in Figure 7 b,c. At first glance it can be observed that ethane and ethene molecules can be sorbed in ZIF-8 at comparable loadings for the higher pressure window of [10,100] bar. The loadings at the maximum pressure studied were c s ethane (273 K, 100 bar) = 22.2 and c s ethene (273 K, 100 bar) = 20.7 molecules/uc, as can be seen in Figure 7b,c.…”

“…Over the last two decades, Zeolitic Imidazolate Frameworks (ZIFs) that form a subclass of Metal Organic Frameworks (MOFs) have received substantial attention for their actual and potential use in catalytic and gas separation processes, CO 2 capture and conversion, water desalination, wastewater treatment, removal of heavy metals, and as heat storage materials. − ZIF porous materials, which closely follow the topology of zeolites, are composed of tetrahedrally coordinated transition metal ions (e.g., Fe, Co, Cu, Zn) connected by imidazolate linkers. The self-assembly of tetrahedral atoms and organic imidazolate linkers gives birth to a large collection of molecular structures, which can have large pore volumes and surface areas, significant resistance to thermal changes, and chemical stability.…”

New Insight into Sorption Cycling Stability of Three Al-Based MOF Materials in Water Vapour

“…The latter stimulated an intensive research on their water sorption properties and function, as well as on their sensitivity or instability in the presence of moisture and other agents [9][10][11]. To date, numerous studies on water sorption in MOFs from the heat-reallocation-applications viewpoint of view have been published [12][13][14][15][16][17], with a recent emphasis on aluminium MOFs as environmentally benign and stable MOFs [15][16][17][18].…”

Preparation of ZIF-8-coated silica hard-shell microcapsule by semi-batch operation

“…These have been widely investigated for various applications such as catalysis, 15 gas separation, 16 enzyme immobilization, 17,18 and heat storage. 19 These ZIFs can be synthesized in an aqueous solution. [20][21][22][23][24][25][26] Furthermore, synthesizing these ZIFs in water solvent is advantageous because ZIF synthesis can proceed at approximately 293 K and no high-temperature heat treatment is required.…”