Self-sacrificial synthesis of Cu<sub>3</sub>(HHTP)<sub>2</sub> on Cu substrate for recyclable NH<sub>3</sub> gas adsorption with energy-efficient photothermal regeneration.

Abstract

The efficient adsorption and removal of toxic gases, particularly ammonia (NH₃), remains a critical challenge in environmental management and industrial safety. Metal-organic frameworks (MOFs) have emerged as promising gas adsorbents due to their tunable structures and high surface area. However, the strong interaction between NH₃ and MOFs poses challenges for the regeneration and reusability of MOF adsorbents, often requiring energy-intensive desorption methods. This study proposes a sustainable approach for regenerating adsorption sites for recyclable gas adsorbents. We present a facile method for the direct synthesis of Cu₃(HHTP)₂ on a Cu mesh substrate (Cu₃(HHTP)₂@Cu), utilizing the Cu metal itself as a precursor to eliminate the need for external metal sources. The resulting Cu₃(HHTP)₂@Cu serves as a recyclable NH₃ adsorbent, leveraging the π-conjugated hexahydroxytriphenylene (HHTP) ligand for photothermal conversion under sunlight irradiation, where photo-generated heat facilitates NH₃ desorption. The study further explores the effect of an external voltage on the NH₃ adsorption performance and crystalline structure of Cu₃(HHTP)₂@Cu. Our findings demonstrate that Cu₃(HHTP)₂@Cu achieves efficient NH₃ desorption through a minimally invasive and energy-efficient mechanism, addressing the limitations of conventional adsorbents.