LiCl modified MOFs-derived porous carbon hollow spheres for efficient solar-driven atmospheric water harvesting

Abstract

Developing adsorbents with excellent photothermal and water uptake properties for solar-driven sorption-based atmospheric water harvesting (SAWH) is full of challenging, which requires a balance between the adsorption capacity, hydrophilicity, and photothermal performance of adsorbent. In this work, a LiCl modfiied porous carbon hollow microspheres (CHM@LiCl) adsorbent with high adsorption capacity (2.07 g g⁻¹) at 100% RH and enhanced low moisture adsorption performance was synthesized by loading LiCl hydrophilic adsorption sites into MOFs-derived hollow porous carbon. LiCl, as the main adsorption site, enhances the hydrophilicity of the CHM@LiCl adsorbent, and its water uptake capacity at 20% RH, 40% RH, 60% RH, and 80% RH are 0.25, 0.39, 0.60 and 1.04 g g⁻¹, respectively. In addition, the hiearchical porous structure of the hollow carbon with mciroporus shell effectively suppresses the salt leakage during water adsorption. The sorbent exhibites stable performance for cycling water adsorption-release, indicating its long-term reliability. The excellent photothermal performance of CHM@LiCl adsorbent can quickly heat up to 67 °C under one sun irradiation, and completely desorb the adsorbed water within 30 minutes. The outdoor water harvesting experiment shows that the CHM@LiCl adsorbent holds great potential for practical solar-driven SAWH with a water collection capacity of 3.3 L_water kg_sorbent⁻¹ day under RH 60%.