Generic Postfunctionalization Route from Amino-Derived Metal-Organic Frameworks Marie Savonnet, †,‡ Delphine Bazer-Bachi, ‡ Nicolas Bats, ‡ Javier Perez-Pellitero, ‡ Erwann Jeanneau, § Vincent Lecocq, ‡ Catherine Pinel, † and David Farrusseng* ,† IRCELYON, Institut de recherches sur la catalyse et l’enVironnement de Lyon; UniVersite ´ Lyon 1 - UMR 5256 CNRS, 2 aVenue Albert Einstein, F-69626 Villeurbanne Cedex, France, IFP-Lyon, BP n°3, 69360 Solaize, France, and UniVersite ´ Lyon 1, Centre de Diffractome ´trie, 69629 Villeurbanne Cedex, France Received November 12, 2009; E-mail: david.farrusseng@ircelyon.univ-lyon1.fr The secondary building unit (SBU) approach for engineering of metal-organic frameworks (MOFs) with tunable pore sizes is very attractive for designing practical properties such as separation by molecular sieving and shape-selective catalysis. 1 The conceptual approach used to increase the pore sizes of MOFs through the use of longer ligands has also been extended to the design of multifunctional MOFs bearing a functional group on the organic moiety. This is the case for IRMOF-3, 2 MOF-101(-Br), 3 and MIL- 53(Al)-NH 2 , 4 to name a few. However, this extension is not straightforward in practice. 5 Indeed, the chemistry of MOF network formation is very sensitive to the chemical reactivity and solubility of the functionalized linkers. 6 This is particularly the case for functions such as -OH, -COOH, and N-donating groups, which can interfere with the coordination chemistry associated with the assembly of the nodes. When self-assembly fails in the synthesis of an MOF with functionalized linkers, the postfunctionalization of a parent MOF appears to be a very valuable alternative. 7 In fact, postsynthesis opens the door to advanced porous solid engineering by multiple synthesis steps 8 and, as a consequence, to the design of new types of adsorbents and catalysts. Postfunctionalization consists of modifying the organic part of the MOF by a chemical reaction that takes place within the porous framework. In this case, the parent MOF must possess accessible reactive functions. Similar issues have been resolved for MCM-like materials, for which various func- tionalization methods have been developed. 9 In a similar fashion to alkylamino-functionalized MCMs, 10 amino-derived MOFs such as IRMOF-3 and DMOF-NH 2 11 are excellent platforms for the grafting of various synthons such as aldehydes, isocyanates, and acid anhydrides. That said, the suitability, diversity and availability of such synthons can appear limited when one considers the ever- increasing demands for different functionalities and the ambitious projects imagined by chemists. Valuable alternatives lie in the development of all kinds of generic postfunctionalization methods that are soft, do not liberate byproducts that may react or remain blocked in the pores, and enable grafting of a wide variety of chemical functions with high efficiency and selectivity. The Sharpless “click” reaction using Cu I -catalyzed Huisgen cycloaddition of azides to alkynes fulfills all of these criteria. 12,13 The corresponding azide linkers are, however, highly unstable and not commercially available; this significantly limits the synthesis of MOFs bearing azide groups by self-assembly methods. The objective of this work was to develop a one-pot, two-step functionalization method starting from already available amino- derived MOF compounds. 14 The first step involves an original method to convert a MOF in its amino form to the corresponding azide compound. Next, the desired functionalized material is obtained by “clicking” a synthon onto the azide without isolation of the intermediate. The starting materials DMOF-NH 2 [Zn(bdc-NH 2 )(DABCO)] (section S1 in the Supporting Information) and MIL-68(In)-NH 2 [In(OH)(bdc-NH 2 )] 15 (section S5) were selected as representative compounds. The former is a zero-dimensional-type MOF with a layered structure made of Zn carboxylate sheets supported by 1,4- diazabicyclo(2.2.2)octane (DABCO) pillars. It is representative of a large class of porous coordination polymers (PCPs). 16 On the other hand, MIL-68(In)-NH 2 belongs to another important class of MOFs characterized by a one-dimensional rod-shaped structure. This class has been reviewed by Yaghi et al. 17 It should be noted that the usual route for preparing azide compounds from the corresponding amines via their diazonium salts cannot be applied here because DMOF-NH 2 dissolves under acidic conditions. Instead, we investigated another pathway that uses mild conditions and involves stable, nonexplosive compounds. 18 In a typical synthesis (Scheme 1), the freshly dried DMOF-NH 2 was treated with tBuONO and TMSN 3 in THF overnight at room temperature to produce the corresponding azide intermediate compound DMOF-N 3 . 19 In the same vessel, the functionalized DMOF (DMOF-fun) was obtained by addition of excess pheny- lacetylene in the presence of Cu I (CH 3 CN) 4 PF 6 followed by continu- ous stirring for 24 h (section S3). For characterization purposes, the synthesis was stopped after formation of the azide intermediate DMOF-N 3 . MIL-68(In)-NH 2 was modified by applying a similar procedure. 20 For sake of brevity, details are given in section S6 in the Supporting Information. Clear proof of azide formation and the subsequent (3 + 2) cycloaddition was obtained by IR spectroscopy. The absorption band of DMOF-N 3 at 2123 cm -1 is characteristic of the N 3 asymmetric stretching vibration (section S3). In addition, unam- biguous characterization and quantification were provided by liquid † IRCELYON UMR 5256 CNRS. ‡ IFP-Lyon. § Universite ´ Lyon 1. Scheme 1. One-Pot, Two-Step Functionalization of DMOF-NH 2 Published on Web 03/16/2010 10.1021/ja909613e  2010 American Chemical Society 4518 9 J. AM. CHEM. SOC. 2010, 132, 4518–4519