High pressure methane adsorption in the metal-organic frameworks Cu3(btc)2, Zn2(bdc)2dabco, and Cr3F(H2O)2O(bdc)3

Three porous coordination polymers Cu 3 (btc) 2 (HKUST-1) (btc = benzene-1,3,5-tricarboxylate) ( 1 ), Zn 2 (bdc) 2 dabco ( 2 ) (bdc = benzene-1,4-dicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane), and Cr 3 F(H 2 O) 2 O(bdc) 3 (MIL-101) ( 3 ) were evaluated as methane storage materials. The compounds were synthesized using solvothermal method and identified as pure phases using powder X-ray diffraction. Nitrogen physisorption at 77 K revealed a high specific micropore volume ranging from 0.75 to 1.303 cm 3 g −1 . Methane adsorption isotherms were measured using gravimetric method at 303 K up to 200 bar. A volumetric miniature tank system was used to measure the effective volumetric storage capacity taking the packing density into account. Among the three materials, Cu 3 (btc) 2 shows the highest excess adsorption at 303 K (15.7 wt.%) and effective volumetric storage capacity of 228 m 3 m −3 (150 bar), whereas for Zn 2 (bdc) 2 dabco and MIL-101 the maximum excess adsorption is lower (14.3 and 14.2 wt.%, respectively). For MIL-101, the maximum in the excess adsorption is observed at higher pressure (125 bar) as compared to Cu 3 (btc) 2 and Zn 2 (bdc) 2 dabco (75 bar).