Metal-organic framework materials for adsorption heat pumps

Adsorption technology offers a potential in vital applications like energy storage, cooling and heating, and water desalination which can be driven by low-grade or renewable heat sources leading to significant reduction in CO₂ emissions. The adsorbent material is a key element in adsorption heat pump systems determining the performance, size and cost of such technology. Metal-organic frameworks (MOFs) are class of adsorbents with superior water uptake, high pore volume and surface area. This study describes the experimental testing of adsorption heat pumps using aluminium fumarate, CPO-27(Ni) and MIL-100(Fe) for various adsorption applications. Results showed that energy storage density of 1200 W h kg⁻¹ was achieved using MIL-100(Fe) regenerated at 95°C, and cycle time of 90 min. For cooling applications, MIL-100(Fe) showed high specific cooling power of 226 W kg⁻¹ at 95°C while aluminium fumarate produced 136 W kg⁻¹ specific cooling power (SCP) at 90°C. Regarding water desalination, MIL-100(Fe) showed high water production rate specific daily water production (SDWP) of 19 m³ ton⁻¹ day⁻¹. For power generation, including a turbine in the adsorption system can increase the effective coefficient of performance (COP) of the adsorption cooling system by 22%. Integrating the adsorption cooling system with Organic Rankine Cycle (ORC) can produce an effective COP of 0.8.