Copper insertion in a series of metal-organic frameworks with uncoordinated carboxylic acid groups for ammonia removal

Abstract

Metal-organic frameworks are a widely studied class of porous crystalline materials characterized by their high surface areas, porosity and thermal stability. Recent research studies have identified these materials as potential candidates for a wide variety of applications including catalysis, gas adsorption and drug delivery. Among these applications, air purification is of great importance given the need to improve current filter materials to include protection against gases with high vapor pressures such as ammonia. In order to achieve this, materials must be water-stable and, at the same time, have strong interaction sites with ammonia. To this end, this thesis presents the first step in analyzing the performance of MOFs with copper carboxylate functional groups toward ammonia removal from air. The insertion of copper atoms into the UiO-66-COOH and UiO-66-(COOH)2 frameworks was attained by a post-synthetic modification of the materials. All materials were characterized before and after exposure to NH3 vapor, using powder X-ray diffraction (PXRD) and BET modeling of N2 adsorption isotherms. Ammonia breakthrough experiments demonstrate that the metalated materials perform better than UiO-66-COOH and UiO-66-(COOH)2 under dry and humid conditions. In particular, to the best of our knowledge, UiO-66-(COOCu)2 has the highest ammonia dynamic capacity among other UiO-66 functionalities.