New Zeolitic Imidazolate Framework-Derived N-Doped Carbon LiCl Composites for Sorption Thermal Batteries Utilizing Solar Energy

Abstract

The potential of sorption thermal batteries utilizing solar energy is increasingly recognized, but developing cost-effective, stable, and high-performance storage materials remains a major challenge. Here, we demonstrate for the first time the use of zeolitic imidazolate framework (ZIF)-derived nitrogen-doped carbons (ZDCs) as hosts for LiCl-embedded water sorbent composites. ZIF-90 and ZIF-94 were synthesized in acetone–water solvent mixtures and subsequently pyrolyzed at 950°C in argon to obtain N-doped disordered carbons with specific surface areas up to 842 m² g⁻¹, hierarchical porosity, and maximal water adsorption capacity of up to 0.69 g g⁻¹. The structural features of the carbons were elucidated by transmission electron microscopy, X-ray photoelectron spectroscopy, Raman, and solid-state nuclear magnetic resonance spectroscopy. The composites with LiCl, prepared via incipient wetness impregnation, exhibited excellent cycling stability and showed no deliquescence or decrease in water uptake over 50 cycles under adsorption at 30°C, desorption at 120°C, and condensation/evaporation at 10°C. Remarkably, under these conditions, an energy storage density of 966.9 kWh m⁻³ can be achieved. These results show that ZDC-LiCl composites represent a promising class of stable, high-performance materials for efficient sorption thermal batteries.