Metal–Organic Frameworks for Ammonia‐Based Thermal Energy Storage

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202102689.Recently, the application of metal-organic frameworks (MOFs) in thermal energy storage has attracted increasing research interests. MOF-ammonia working pairs have been proposed for controlling/sensing the air quality, while no work has yet been reported on the immense potential of MOFs for thermal energy storage up till now. Herein, the feasibility of thermal energy storage using seven MOF-ammonia working pairs is experimentally assessed. From ammonia sorption stability and sorption thermodynamics results, it is found that MIL-101(Cr) exhibits both high ammonia sorption stability and the largest sorption capacity of ≈0.76 g g −1 . Compared with MIL-101(Cr)-water working pair, MIL-101(Cr)-ammonia working pair improves the sorption capacity by over three times with evaporation temperature lower than 8.4 °C. Due to stable ammonia sorption stability and negligible hysteresis, MIL-101(Cr) and ZIF-8(Zn) are tested at condensation/evaporation temperature of 30 °C/10 °C. The thermal energy storage density (reaching over 1200 kJ kg −1 ) and coefficient of performance of MIL-101(Cr)-based system are both higher than ZIF-8(Zn)-based one due to larger average isosteric enthalpy and cycle sorption capacity. This experimental work paves the way for developing the high efficient and stable thermal energy storage system with MOF-ammonia working pairs especially for critical conditions with low evaporation temperature and high condensation temperature.Research data are not shared.

Metal–organic frameworks for NH3 adsorption by different NH3 operating pressures

“…An et al suggested MIL-101 as the most suitable MOF for high-pressure NH 3 adsorption and desorption due to its high specific surface area and large pore size. 29 Chemical equilibrium between a metal center and NH 3 could affect the structural stability of MOFs, and strong bonding between a metal center and an organic linker could be helpful to maintain the framework stability upon NH 3 adsorption-desorption cycles. Moreover, improvement of NH 3 adsorption-desorption rates in MOFs would allow efficient mass and heat transfer in AHPs.…”

“…Yet, only few articles have recently appeared to demonstrate MOFs as potential NH 3 adsorbents in AHPs (Table 1). [27][28][29] We begin to introduce the operating principle of AHPs for better understanding important requirements of MOFs under high-pressure NH 3 environment. AHPs provide heating or cooling from thermal energy, different from compression heat pumps operated by mechanical energy.…”

“…Yet, only few articles have recently appeared to demonstrate MOFs as potential NH 3 adsorbents in AHPs (Table 1). 27–29 …”

Silver-Nanoparticle-Assisted Modulation of NH3 Desorption on MIL-101

“… 26 Recent reports for high-pressure ammonia adsorption demonstrated that MIL-101 was evaluated as the most stable MOF with higher ammonia uptake than other MOFs (MOF-801, MOF-841, DUT-67, NU-1000, UiO-66, and MIL-100). 7 , 27 In addition, introducing heterogeneous metal components has shown synergistic effects in gas adsorption and catalysis. 28 − 33 Noble metals (Pt, Pd, Rh, Au, and Ag) have strong affinity for ammonia, 34 and silver nanoparticles could display increasing selectivity for ammonia sensing on carbon nanotubes.…”

“…MIL-101 consists of μ 3 -oxo bridged chromium-trimers with terephthalic acid ligands, and it has a relatively large surface area with hierarchical pore structures and high structural stability against water, oxygen, organic solvents, and heat . Recent reports for high-pressure ammonia adsorption demonstrated that MIL-101 was evaluated as the most stable MOF with higher ammonia uptake than other MOFs (MOF-801, MOF-841, DUT-67, NU-1000, UiO-66, and MIL-100). , In addition, introducing heterogeneous metal components has shown synergistic effects in gas adsorption and catalysis. − Noble metals (Pt, Pd, Rh, Au, and Ag) have strong affinity for ammonia, and silver nanoparticles could display increasing selectivity for ammonia sensing on carbon nanotubes . We anticipated that relatively low ammonia desorption energy and cost of Ag among the noble metals would be desirable for the heterogeneous component encapsulated in MIL-101.…”