Visible ozone detection and removal in two-dimensional Mn(ii)-based metal–organic frameworks

Abstract

Atmospheric ozone (O₃) has long been a threat to human health, however, rational design of dual-function materials for straightforward sensing and removal of trace O₃ in the environment (air, water, etc.) remains challenging. Herein, we present a highly stable and hydrophobic two-dimensional Mn(II)-based metal–organic framework (denoted as BUT-82), which shows distinctive color change on exposure to O₃ in air or in liquid water due to the oxidation of Mn²⁺. The O₃ concentration could be quantified by analyzing the color changes of BUT-82 using UV/Vis spectroscopy or more facilely using smartphone photography, and the limits of detection for O₃ of the two methods were 47 and 274 ppb, respectively. In addition, BUT-82 showed apparently higher capacity for the removal of O₃ from dry or highly humid air flows than its starting materials, namely MnCl₂·4H₂O and a dicarboxylic acid ligand containing a long alkyl chain (3,3′-bis(dodecyloxy)-[1,1′-biphenyl]-4,4′-dicarboxylic acid). Isoreticular expansion of the MOF to tune its performance was also proven feasible. This work offers new insights into the development of new materials for O₃ pollution control.