Yang Yajie, Faheem Muhammad, Wang Lili, Meng Qinghao, Sha Haoyan, Yang Nan, Yuan Ye, Zhu Guangshan
Key Laboratory of Polyoxometalate Science of Ministry of Education, Northeast Normal University, Changchun 130024, P. R. China.
Department of Chemical Engineering, University of California, Davis, Davis, California 95616, United States.
ACS Cent Sci. 2018 Jun 27;4(6):748-754. doi: 10.1021/acscentsci.8b00232. Epub 2018 Jun 6.
Ammonia (NH) is a commonly used industrial gas, but its corrosiveness and toxicity are hazardous to human health. Although many adsorbents have been investigated for NH sorption, limited ammonia uptake remains an urgent issue yet to be solved. In this article, a series of multivariate covalent organic frameworks (COFs) are explored which are densely functionalized with various active groups, such as -N-H, -C=O, and carboxyl group. Then, a metal ion (Ca, Mn, and Sr) is integrated into the carboxylated structure achieving the first case of an open metal site in COF architecture. X-ray photoelectron spectroscopy reveals conclusive evidence for the multiple binding interactions with ammonia in the modified COF materials. Infrared spectroscopy indicates a general trend of binding capability from weak to strong along with -N-H, -C=O, carboxyl group, and metal ion. Through the synergistic multivariate and open metal site, the COF materials show excellent adsorption capacities (14.3 and 19.8 mmol g at 298 and 283 K, respectively) and isosteric heat () of 91.2 kJ mol for ammonia molecules. This novel approach enables the development of tailor-made porous materials with tunable pore-engineered surface for ammonia uptake.
氨（NH₃）是一种常用的工业气体，但其腐蚀性和毒性对人体健康有害。尽管已经研究了许多用于氨吸附的吸附剂，但氨吸收量有限仍然是一个亟待解决的紧迫问题。在本文中，探索了一系列多元共价有机框架（COF），它们用各种活性基团如-N-H、-C=O和羧基进行了密集功能化。然后，将金属离子（Ca、Mn和Sr）整合到羧基化结构中，实现了COF结构中首例开放金属位点。X射线光电子能谱揭示了改性COF材料中与氨发生多重结合相互作用的确凿证据。红外光谱表明，随着-N-H、-C=O、羧基和金属离子的出现，结合能力呈现从弱到强的总体趋势。通过协同的多元和开放金属位点，COF材料表现出优异的吸附容量（在298 K和283 K时分别为14.3和19.8 mmol g⁻¹）以及氨分子的等量吸附热（91.2 kJ mol⁻¹）。这种新颖的方法能够开发出具有可调孔工程表面的定制多孔材料用于氨吸收。
