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Ammonia Capture within Isoreticular Metal-Organic Frameworks with Rod Secondary Building Units

submitted on 02.08.2019 and posted on 05.08.2019 by Shinya Moribe, Zhijie Chen, Selim Alayoglu, Zoha H. Syed, Timur Islamoglu, Omar K. Farha
The efficient removal, capture, and recycling of ammonia (NH3) constitutes a demanding process, thus the development of competent adsorbent materials is highly desirable. The implementation of metal-organic frameworks (MOFs), known for their tunability and high porosity, has attracted much attention for NH3 adsorption studies. Here, we report three isoreticular porphyrin-based MOFs containing aluminum (Al-PMOF), gallium (Ga-PMOF), and indium (In-PMOF) rod secondary building units with Brønsted acidic bridging hydroxyl groups. NH3 sorption isotherms in Al-PMOF demonstrated reversibility in isotherms. In contrast, the slopes of the adsorption isotherms in Ga-PMOF and In-PMOF were much steeper than Al-PMOF in lower pressure regions, with a decrease of NH3 adsorbed amounts observed between first cycle and second cycle measurements. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) suggested that the strength of the Brønsted acidic -OH sites was controlled by the identity of the metal, which resulted in stronger interactions between ammonia and the framework in Ga-PMOF and In-PMOF compared to Al-PMOF.




Email Address of Submitting Author


Northwestern University, Toyota Motor North America


United States

ORCID For Submitting Author


Declaration of Conflict of Interest

The authors declare no competing financial interest.