Solid–liquid interface synthesis of microcrystalline porous coordination networksw Javier Martı´-Rujas, a Yoshitaka Matsushita, b Fujio Izumi, c Makoto Fujita a and Masaki Kawano* d Received 27th April 2010, Accepted 20th July 2010 DOI: 10.1039/c0cc01141j Solid–liquid interface synthesis provided a unique way to selectively and efficiently prepare molecular complexes (ML 2 ) and metastable porous coordination networks in short crystalli- zation times. In sharp contrast, their solution reactions gave interpenetrated open-framework networks. We succeeded in solving a crystal structure of the metastable network by ab initio powder X-ray analysis. Typical synthetic methods in coordination networks involve solution synthesis via self-assembling using layer diffusion or at higher temperatures under hydrothermal or solvothermal conditions. 1 Less common synthetic routes in coordination networks include microwave, 2 microemulsion 3 and recently electrochemical synthesis. 4 Such methods use a substantial amount of solvents often acting as structure directing agents (template) for the formation of the extended networks. 5 Usually the above methods yield crystals of good quality for single crystal X-ray diffraction. 6 However, synthetic methods that yield poorly crystalline materials or microcrystalline solids are far less exploited due to the difficulties in obtaining the X-ray structures from single crystal X-ray diffraction. Here, for the first time we report the solid–liquid interface syntheses of two microcrystalline compounds: (i) a discrete molecular complex [(ZnCl 2 )(TPT) 2 ]2(H 2 O) ( ML 2 where TPT = 2,4,6-tris(4-pyridyl)triazine), see ESIw) and (ii) a mix-halide one-dimensional (1D) metastable porous coordi- nation network [(ZnCl 2 )(ZnBr 2 ) 2 (TPT) 2 ] n m(CH 3 OH) (1) built up by self-assembling of ML 2 and ZnBr 2 (Fig. 1). Remarkably the 1D coordination network retains porosity up to 543 K. However, in solution, 1 transforms via a thermo- dynamically favored network, [(ZnCl 2 )(ZnBr 2 ) 2 (TPT) 2 ] n , (phase I) to a nonporous 1D coordination network [(ZnBr 2 )(TPT)] n (2) (Fig. 2). 7 In sharp contrast, their solution syntheses using the same starting materials gave totally different networks, that is, interpenetrated open-framework networks, [(ZnCl 2 ) 3 (TPT) 2 ] n and [(ZnBr 2 ) 3 (TPT) 2 ] n , respectively. 8 Note- worthy is that ML 2 and 1 can be prepared via only solid–liquid interface reaction. The new porous coordination polymer we discuss herein was prepared by suspending the complex ML 2 (22 mg, 0.03 mmol) in a ZnBr 2 (40.54 mg, 0.18 mmol) methanol solution (8 mL) at 275 K (Fig. 1). The suspension was vigorously stirred for 15 min. A white powder was collected. Because the ML 2 is hardly soluble in methanol, it is very likely that the solid residue ML 2 reacts via solid–liquid interface. The white powder was quickly filtered, vacuum dried and sealed in a glass capillary. Powder X-ray diffraction (PXRD) experiments clearly showed that the crystalline material is completely different from both ML 2 and ligand TPT (see ESIw).z Elemental analysis suggests that the white powder after drying is a mixed halide network, [(ZnCl 2 )(ZnBr 2 ) 2 (TPT) 2 ] n m(CH 3 OH) (1). Remarkably, we can control the product formation upon Fig. 1 Solid–liquid interface syntheses of ML 2 and 1. Fig. 2 Energy diagram showing the formation of 1 through the solid–liquid interface reaction. In solution, 1 transforms via the inter- mediate thermodynamically favoured network phase I (dashed line) to 2. a Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan b Beamline BL15XU, SPring-8, NIMS-branch office, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148, Japan c Quantum Beam Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan d The Division of Advanced Materials Science, Pohang University of Science and Technology, (POSTECH), San 31 Hyojadong, Pohang, 790-784, South Korea. E-mail: mkawano@postech.ac.kr; Fax: +82 54 279 8736; Tel: +82 54 279 8740 w Electronic supplementary information (ESI) available: For the synthesis, elemental analyses and structural determination of ML 2 , 1 and 1G 1 . CCDC 746217 (ML 2 ), 760714 (1), 760715 (1G 1 ). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0cc01141j This journal is  c The Royal Society of Chemistry 2010 Chem. Commun., 2010, 46, 6515–6517 | 6515 COMMUNICATION www.rsc.org/chemcomm | ChemComm Downloaded by POLITECNICO DI MILANO on 27 August 2010 Published on 10 August 2010 on http://pubs.rsc.org | doi:10.1039/C0CC01141J View Online