Tunable Ammonia Adsorption within Metal-Organic Frameworks with Different Unsaturated Metal Sites.

Ammonia (NH) emissions during agricultural production can cause serious consequences on animal and human health, and it is quite vital to develop high-efficiency adsorbents for NH removal from emission sources or air. Porous metal-organic frameworks (MOFs), as the most promising candidates for the capture of NH, offer a unique solid adsorbent design platform. In this work, a series of MOFs with different metal centers, ZnBTC, FeBTC and CuBTC, were proposed for NH adsorption. The metal centers of the three MOFs are coordinated in a different manner and can be attacked by NH with different strengths, resulting in different adsorption capacities of 11.33, 9.5, and 23.88 mmol/g, respectively. In addition, theoretical calculations, powder XRD patterns, FTIR, and BET for the three materials before and after absorption of ammonia were investigated to elucidate their distinctively different ammonia absorption mechanisms. Overall, the study will absolutely provide an important step in designing promising MOFs with appropriate central metals for the capture of NH.