A novel copper-based MOF material: Synthesis, characterization and adsorption studies J. Lincke a , D. Lässig a , J. Moellmer b , C. Reichenbach c , A. Puls d , A. Moeller b , R. Gläser a , G. Kalies c , R. Staudt e,⇑ , H. Krautscheid a,⇑ a Universität Leipzig, Fakultät für Chemie und Mineralogie, Johannisallee 29, D-04103 Leipzig, Germany b Institut für Nichtklassische Chemie e.V., Permoserstr. 15, D-04318 Leipzig, Germany c Universität Leipzig, Fakultät für Physik und Geowissenschaften, Linnéstraße 5, D-04103 Leipzig, Germany d Rubotherm GmbH, Universitätsstr. 142, D-44799 Bochum, Germany e Hochschule Offenburg, Fakultät Maschinenbau und Verfahrenstechnik, Badstraße 24, D-77652 Offenburg, Germany article info Article history: Received 17 August 2010 Received in revised form 18 October 2010 Accepted 1 November 2010 Available online 21 November 2010 Keywords: Coordination polymer MOF Crystal structure Adsorption isotherms Secondary building unit abstract Synthesis and crystal structure of a novel copper-based MOF material are presented. The tetragonal crys- tal structure of 3 1 ½ðCu 4 ðl 4 -OÞðl 2 -OHÞ 2 ðMe 2 trzpbaÞ 4  possesses a calculated solvent-accessible pore vol- ume of 57%. Besides the preparation of single crystals, synthesis routes to microcrystalline materials are reported. While PXRD measurements ensure the phase purity of the as-synthesized material, TD-PXRD measure- ments and coupled DTA–TG–MS analysis confirm the stability of the network up to 230 °C. The pore volume of the microcrystalline material determined by nitrogen adsorption at 77 K depends on the synthetic conditions applied. After synthesis in DMF/H 2 O/MeOH the pores are blocked for nitrogen, whereas they are accessible for nitrogen after synthesis in H 2 O/EtOH and subsequent MeOH Soxhleth extraction. The corresponding experimental pore volume was determined by nitrogen adsorption to be V Pore ¼ 0:58 cm 3 g 1 . In order to characterize the new material and to show its adsorption potential, comprehensive adsorp- tion studies with different adsorptives such as nitrogen, argon, carbon dioxide, methanol and methane at different temperatures were carried out. Unusual adsorption–desorption isotherms with one or two hys- teresis loops are found – a remarkable feature of the new flexible MOF material. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction In recent years, metal organic frameworks (MOFs), i.e. porous three-dimensional coordination polymers, become more and more interesting since their matrix and pore characteristics (high specific surface area and microporosity, definite pore size distri- bution, structural regularity, flexibility, etc.) promise applications in gas storage, catalysis, ion exchange, separation, polymeriza- tion, etc. [1]. In this way, the number of microporous solids such as zeolites and activated carbons applicable in chemical industry is extended. The first structures of coordination polymers have been already reported in the early 1960s [2–4], but with the synthesis of HKUST- 1 (Cu 3 (btc) 2 , btc = 1,3,5-benzene tricarboxylate) and MOF-5 in 1999 [5,6], MOF materials became really popular. HKUST-1 and the recently presented DUT-6 possess impressive high specific sur- face areas [5,7,8]. With regard to the search for applications of MOFs it is advan- tageous that a vast variety of metal ions, i.e. inorganic nodal points [9], and organic linkers can be used to synthesize different struc- tures of coordination polymers. Pure carboxylate ligands have been extensively studied as polyfunctional organic linkers [6,10,11]. In our work, we have found that a combination of carboxylates and nitrogen rich donor groups such as 1,2,4-triazoles possesses prom- ising coordination chemistry for the synthesis of MOFs [12]. Up to now there are only few examples in the literature of such kinds of ligands [13–19]. Recently, we have investigated their coordination behavior towards transition metal ions and the properties of the resulting coordination polymers. One purpose of this paper is to present the crystal structure of a newly synthesized 3 1 ½ðCu 4 ðl 4 -OÞðl 2 -OHÞ 2 ðMe 2 trzpbaÞ 4  Cu-MOF material with the 4-(3,5-dimethyl-4H-1,2,4-triazol-4-yl)benzoate (Me 2 trzpba)  ligand (see Fig. 1). MOFs with highly charged, pure carboxylate ligands often have the disadvantage of charged networks containing counter ions, 1387-1811/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2010.11.017 ⇑ Corresponding authors. E-mail addresses: Reiner.Staudt@fh-offenburg.de (R. Staudt), Krautscheid@rz. uni-leipzig.de (H. Krautscheid). Microporous and Mesoporous Materials 142 (2011) 62–69 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso