Photothermal-assisted NH₃ release in a bipyridinium-functionalized metal-organic framework adsorbent.

Abstract

Widespread deployment of NH₃-adsorbing MOF materials remains challenging due to the significant energy-penalty of regeneration. In this work, we address this limitation by integrating photothermal technologies into a bipyridinium-functionalized MOF matrix, enabling effective NH₃ desorption in a more eco-friendly and sustainable manner. This MOF adsorbent exhibits selective NH₃ capture via specific hydrogen bonding interactions, rendering it suitable for purifying effluent gases in industrial NH₃ synthesis. The NH₃ adsorption process is accompanied by an obvious color change due to the formation of bipyridinium radicals through an electron transfer reaction between NH₃ molecules and bipyridinium ligands. This distinctive property endows the MOF with favorable NH₃ detection capabilities. Furthermore, the colored MOF matrix functions as an exceptional photothermal medium under 808 nm laser irradiation, effectively facilitating the release of captured NH₃ molecules through light-triggered localized heating. Importantly, the synthesis of this MOF material can be scaled up to gram-level with minimal complexity using a straightforward one-pot reflux method, significantly enhancing its practical applicability.