Postsynthetic Modification of a Metal–Organic Framework for Stabilization of a Hemiaminal and Ammonia Uptake

In our study, we show by solid-state (15)N NMR measurements that an important zirconium metal-organic framework (UiO-66) with amino-functionalized links is composed of a mixture of amino and -NH(3)(+)Cl(-) salt functionalities rather than all amino functionality to give a composition of Zr(6)O(4)(OH)(4)(BDC-NH(2))(4)(BDC-NH(3)(+)Cl(-))(2) (UiO-66-A). UiO-66-A was postsynthetically modified to form a mixture of three functionalities, where the hemiaminal functionality is the majority species in UiO-66-B and aziridine is the majority functionality in UiO-66-C. UiO-66-A-C are all porous with surface areas ranging from 780 to 820 m(2)/g and have chemical stability, as evidenced by reversible ammonia uptake and release showing capacities ranging from 134 to 193 cm(3)/g.