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

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 degrees 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 P (1) over bar space group with a = 5.25 angstrom, b = 9.67 angstrom, c = 10.77 angstrom, a = 90.29 degrees, beta = 91.06 degrees, gamma = 92.413 degrees, and V = 546.04 angstrom(3). The Brunauer-Emmett-Teller (BET) surface area was 903 m(2)g(-1) with 777 m(2)g(-1) of micropore surface area. The uptake of CO2 and CH4 up to 20 bar were 5.2 and 2.7 mmolg(-1), respectively. These values are compared to those of 1,3,5-benzenetricarboxylate [Cu-3(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.