Enhanced Ammonia Sorption Performance via NH4Cl-Impregnated MIL-101(Cr) for Low-Grade Heat Utilization

Abstract

Efficient ammonia (NH3) adsorption and desorption under high-pressure conditions are crucial for advancing adsorption-driven thermal energy storage (TES) and heating/cooling systems. In this study, NH4Cl-impregnated MIL-101(Cr) composites were synthesized to enhance NH3 sorption performance. The strong NH4 +-Cl- interactions within the metal-organic framework (MOF) scaffold provides abundant active sites, while the porous MIL-101(Cr) matrix ensures rapid NH3 diffusion and uniform NH4Cl distribution. This synergistic architecture significantly improves adsorption kinetics, cyclic stability, and desorption efficiency under mild thermal conditions. The optimized composite (MN1.70) exhibits an NH3 uptake of 0.79 +/- 0.02 g/g at 6.2 bar and 25 degrees C, along with excellent reversibility and a fast sorption rate (similar to 0.14 mg/g/s). System-level analysis based on these properties indicates a 7% improvement in energy storage capacity compared to the best previously reported sorption-based TES systems. These findings highlight the potential of NH4Cl-MOF composites as promising candidates for low-temperature NH3-based thermal energy management, particularly in industrial applications utilizing waste heat and renewable sources.