Antenna-Protected Metal-Organic Squares for Water/Ammonia Uptake with Excellent Stability and Regenerability

Ammonia is a hazardous gas and the only carbon-free chemical energy carrier that can be largely adsorbed on metal organic frameworks (MOFs). However, because of the destructive effect of H2O/NH3 on the metal nodes, most MOFs cannot be applied in ammonia capture and uptake. Herein, three Co-4,5-imidazoledicarboxylic series metal organic squares (MOSs)-Co-4(IDC)(4)(pda)(4), Co-4(IDC)(4)(phen)(4), and Co-4(IDC)(4)(bpy)(4) were synthesized with a special independent square configuration and zeolitelike supramolecular structures, and their structure and H2O/NH3 uptake capacity were investigated. Based on the four antennas-protected squares and porous structures, the three MOSs have excellent H2O/NH3 stability, whose structures were not affected by the ad-desorption of H2O, NH3, or H2O/NH3. The three MOFs have a H2O uptake of 17.63, 8.35, and 7.75 mmol/g, respectively, as well as the facile release and repeatable of high ammonia uptakes of 11.5, 5.2, and 3.8 mmol/g, respectively. In addition, the MOFs have good stability and ammonia adsorption (4.73, 2.33, and 1.21 mmol/g, respectively) under humid conditions. Therefore, the three MOSs may be sustainably applied to ammonia uptake applications, because of their high ammonia uptake, ease of release, and the unique structural protection effect of the antenna ligands.