Transitional metal-doped aluminum fumarates for ultra-low heat driven adsorption cooling systems

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.