Porous 10- and 12-vertex (bi)-p-dicarba-closo-boranedicarboxylates of cobalt and their gas adsorptive properties.

Two new porous coordination polymers, [Co 3 (μ 3 -OH)(Bcb10DC) 2.5 (DEF) 3 (EtOH) 1.5 (H 2 O) 0.5 ] · DEF · EtOH ( 3b ) and [Co 2 (Bcb12DC) 2 (DMF) 4 (EtOH)] · 2EtOH ( 4 ) based on 10- and 12-vertex p- bicarboranedicarboxylic acids, 1,1′-bi-(1,10-dicarba- closo -decaborane)-10,10′-dicarboxylic acid (H 2 Bcb10DC) and 1,1′-bi-(1,12-dicarba- closo -decaborane)-12,12′-dicarboxylic acid (H 2 Bcb12DC) were synthesized. Their properties were compared with the two known analogues based on shorter ligand-homologues, [Co(cb10DC)(DMF)] ( 1 ) and [Co 4 (OH) 2 (cb12DC) 3 (DMF) 2 (H 2 O) 4 ] · 3DMF · EtOH ( 2 ). The structure of 3b is based on a trinuclear cluster and has a 3D structure with a 5-c bnn underlying net, while 4 is based on a binuclear cluster and composed of stacked 2D sql layers. Activated 3′ with altered structure has S BET (N 2 ) of 1012 m 2  g −1 and 4′ with mostly retained structure 920 m 2 g −1 . Gas adsorption by 3′ and 4′ at 1 bar is: 80.1 cm 3  g -1 (0.72% wt ) and 81.3 cm 3  g -1 (0.73% wt ) H 2 at 77 K; 16.7 and 21.9 cm 3  g -1 CO 2 at 273 K; 6.2 and 10.0 cm 3  g -1 of CH 4 at 273 K. The isosteric heat of adsorption Q st at zero coverage are respectively: 5.0 and 4.5  kJ mol −1 for H 2 , 16.7 and 21.9 for CO 2 ; 6.2 and 10.0 for CH 4 . 2′ with ∼ 645 m 2  g −1 (calc. 883 m 2 g −1 ) has the highest mass-specific H 2 adsorption, >30% than other compounds, while Q st is close to 1′ and slightly higher than for 3′ and 4´ . Adsorption of CO 2 and CH 4 and Q st are ∼1.5–2 times lower for 3′ and 4′ compared to 1′ and 2´ . The surface area specific adsorption of H 2 , CO 2 and CH 4 is the highest for 1´ . The CO 2 /CH 4 IAST selectivities (0.15/0.85; 1 bar, 298 K) are in 2–4.5 range. 3′ and 4′ retain a significant part of porosity after soaking in water unlike 1′ and 2´ . [ABSTRACT FROM AUTHOR]