Synthesis, structure and adsorption properties of a three-dimensional 3-fold interpenetrated Cd(II) coordination network with the rare tfz topology Pei-Chi Cheng a , Yang-Chih Lo a , Wayne Hsu a , Kedar Bahadur Thapa a , Shih-Miao Liou b,⇑ , Jhy-Der Chen a,⇑ a Department of Chemistry, Chung Yuan Christian University, Chung-Li, Taiwan, ROC b Center for General Education, Hsin Sheng Junior College of Medical Care and Management, Longtan, Taiwan, ROC article info Article history: Received 27 February 2015 Accepted 23 April 2015 Available online 1 May 2015 Keyword: Coordination polymer abstract A three-dimensional (3D) coordination network {[Cd 3 (BTC) 2 (L) 3 (H 2 O) 3 ]Á3H 2 O} 1 [L = N,N 0 -di(4-pyridyl)a- dipoamide; H 3 BTC = 1,3,5-benzenetricarboxylic acid], 1, has been synthesized by the hydrothermal reac- tion and characterized by the single crystal X-ray crystallography. Structural analysis reveals that the BTC 3À ligands adopt the l 3 -bonding mode and coordinate to the Cd(II) ions to establish the triangular Cd(II) units, which are linked by the L ligands to form a 3-fold interpenetrated coordination network with the rare tfz topology. Gas adsorption experiments of the desolvated product of 1 show that the H 2 capture is preferable to N 2 and CO 2 . Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Recently, the attentiveness of researchers towards the special characteristics of coordination polymers, i.e. catalysis, magnetism, luminescence and gas adsorption, in addition to their fascinating architectures and topologies, has been concentrated to an increas- ing extent [1,2]. It is widely known that the open structures having high porosities play vital role in determining the efficiency for gas adsorption. However, ‘‘nature abhors a vacuum’’, entanglement in a crystal may happen to maximize its packing efficiency [3]. Interpenetrating network is a significant subclass of entangled sys- tem, in which the voids associated with one network are occupied by one or more independent networks and they can be isolated only by breaking all the internal connections [2(d)]. The pore sizes of such coordination networks can be controlled to achieve selec- tivity in spite of the fact that interpenetration has been regarded as a drawback to porosity [2(e)]. Consequently, the design and syn- thesis of interpenetrating frameworks that show excellent selectiv- ity in gas adsorption is a challenge in the crystal engineering of coordination polymers. The dicarboxylate has been widely used as the auxiliary ligand for the construction of new coordination polymers [4]. We have reported several Cd(II) coordination polymers based on N,N 0 -di(4-pyridyl)adipoamide (L) and dicarboxylate ligands [5]. In this regard, a typical example is the 2-fold interpenetrated coordination network [Cd(bpdc)(L)] n [H 2 bpdc = 4,4 0 -biphenyldicar- boxylic acid] that adopts the pcu topology and revealed that the CO 2 capture is preferable to N 2 in the gas sorption experiments. This result signifies that the amide group of L and the entangle- ment of the coordination network may influence the adsorption of the light gases [5(b)]. Such supportive information encourages us to investigate the role of entanglement of coordination network containing tricarboxylate ligand and L in the gas adsorption. Herein, we report the synthesis, structure and adsorption proper- ties of a three-dimensional 3-fold interpenetrated coordination network {[Cd 3 (BTC) 2 (L) 3 (H 2 O) 3 ]Á3H 2 O} 1 [H 3 BTC = 1,3,5-benzenet- ricarboxylic acid], 1, which shows that H 2 capture is preferable to N 2 and CO 2 in the gas adsorption. The C 3 -symmetric tricarboxylate BTC 3À ligand plays an important structure-directing role in deter- mining the tfz topology of 1. 2. Experimental 2.1. General procedures IR spectra (KBr disk) were obtained from a JASCO FT/IR-460 plus spectrometer. Elemental analyses were obtained from PE 2400 series II CHNS/O analyzer. Thermal gravimetric analyses (TGA) measurements were carried on SII Nano Technology Inc. TG/DTA 6200 over the temperature range of 30–900 °C at a heating rate of 10 °C min À1 under air. Powder X-ray diffraction instrument were carried out on Bruker D2 PHASER diffractometer with Cu Ka (k a = 1.54 Å) radiation. http://dx.doi.org/10.1016/j.poly.2015.04.027 0277-5387/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. Tel.: +886 3 2653351; fax: +886 3 2653399. E-mail addresses: lsm0301@hsc.edu.tw (S.-M. Liou), jdchen@cycu.edu.tw (J.-D. Chen). Polyhedron 96 (2015) 1–5 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly