Photo-triggered modulation of cuprous active sites in metal–organic frameworks for manipulable carbon monoxide capture

Photoresponsive adsorbents have garnered widespread interest on account of their customizable performance under light exposure. However, reported adsorbents of this kind are predominantly engineered to modulate weak interactions between adsorbates and adsorbents via steric hindrance or structural changes. The development of smart adsorbents possessing strong yet adjustable active sites for controllable gas capture presents a significant challenge. Here, we introduced strong active Cu⁺ sites into an azobenzene-modified MOF-808 metal–organic framework to create a smart π-complexation adsorbent. The Cu⁺ sites can selectively interact with CO through π-complexation. This design enables controlled CO capture through light-regulated interactions between the active sites and the azobenzene groups, achieving up to a 31% variation in CO adsorption capacity. Density functional theory calculations indicate that the transformation of azobenzene from the trans to the cis configuration adjusts the surface electrostatic potential near CuCl, reducing Cu⁺ activity. This approach paves the way for target-specific smart adsorption materials.