Structure Solution from Powder Diffraction of Copper 1,4-Benzenedicarboxylate

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Abstract

In the synthesis of the microporous metal–organic framework copper 1,4-benzenedicarboxylate [Cu(BDC)], solvent exchange with methanol prior to recrystallization lowers the desolvation temperature to 160 °C and produces more crystalline Cu(BDC). The solution to the crystal structure of Cu(BDC) has been determined by using ab initio quantum molecular calculations and refinement with synchrotron X-ray powder diffraction data. This solution is in the Pequation image space group with a = 5.25 Å, b = 9.67 Å, c = 10.77 Å, α = 90.29°, β = 91.06°, γ = 92.413°, and V = 546.04 Å3. The Brunauer–Emmett–Teller (BET) surface area was 903 m2 g–1 with 777 m2 g–1 of micropore surface area. The uptake of CO2 and CH4 up to 20 bar were 5.2 and 2.7 mmol g–1, respectively. These values are compared to those of 1,3,5-benzenetricarboxylate [Cu3(BTC)2, HKUST-1] and used to show that the elevated metal-site density per unit volume is responsible for a proportionally higher uptake on the basis of relative surface areas. The platelike particles with perpendicular pores are promising candidates for mixed-matrix membranes.

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