Microporous Materials Constructed from the Interpenetrated Coordination Networks. Structures and Methane Adsorption Properties

Abstract

Five new coordination compounds with 4,4‘-azopyridine (azpy), [Mn(azpy)(NO 3 ) 2 (H 2 O) 2 ]·2EtOH ( 1 ·2EtOH), [Co 2 (azpy) 3 (NO 3 ) 4 ]·Me 2 CO·3H 2 O ( 2 ·Me 2 CO·3H 2 O), [Co(azpy) 2 (NCS) 2 ]·0.5EtOH ( 3 ·0.5EtOH), [Cd(azpy) 2 (NO 3 ) 2 ]·(azpy) ( 4 ·azpy), and [Cd 2 (azpy) 3 (NO 3 ) 4 ]·2Me 2 CO ( 5 ·2Me 2 CO), have been synthesized and structurally characterized. The reaction of Mn(NO 3 ) 2 ·6H 2 O with azpy in ethanol/acetone affords 1 ·2EtOH, whose network consists of one-dimensional chains of [Mn(azpy)(H 2 O) 2 ] n . The chains are associated by hydrogen bonding to provide a logcabin -type three-dimensional structure, which creates about 8 × 8 Å of channels, filled with ethanol molecules. The treatment of Co(NO 3 ) 2 ·6H 2 O and Co(NCS) 2 ·4H 2 O with azpy produces 2 ·Me 2 CO·3H 2 O and 3 ·0.5EtOH, respectively, which have a brick - wall and a rhombus -type two-dimensional networks. The reaction of Cd(NO 3 ) 2 ·4H 2 O with azpy affords 4 ·azpy from the ethanol/H 2 O media, while the reaction in the ethanol/acetone media provides 5 ·2Me 2 CO. 4 ·azpy and 5 ·2Me 2 CO form a square - grid- and a herringbone -type two-dimensional networks, respectively. The two-dimensional sheets of 4 ·azpy stack without interpenetration, leading to large size of channels, which are filled with free azpy molecules. The two-dimensional networks of 2 ·Me 2 CO·3H 2 O, 3 ·0.5EtOH, and 5 ·2Me 2 CO are quadruply, doubly, and triply interpenetrated, respectively. Despite the interpenetration, their networks create the microporous channels filled with guest solvent molecules. The dried compounds 2, 3, and 5 adsorb methane between 1 and 36 atm at 25 °C, in which 3 and 5 exhibit Langmuir-type isotherms. The inherent micropore volumes for 3 and 5 are 0.685 and 3.30 mmol/g, respectively. XRPD measurements under reduced pressure at 100 °C reveal that the channel structure of 3 is the most stable in these compounds; the observed XRPD pattern is in good agreement with that of the simulated pattern of the single-crystal model. Compounds 2 and 5 also retain the porous structures, however, their pore structures are distorted upon loss of guest included molecules.