The structure of a carbon monoxide adduct of zeolite 5A

Abstract

The structure of Ca 5Na 2-A:5CO has been determined at room temperature using Rietveld profile refinement in space groupFm3c witha refined to 24.6558(2)A˚. The finalR pw was 3.5%. As in the case of dehydrated zeolite 5A, the exchangeable cations are located in S1 (6-ring) sites, with Ca-O and Na-O distances of 2.32 and 2.37A˚. The carbon atoms of the carbon monoxide molecules have been located on the three-fold axis in the α-cage in a position analogous to that found in the CO complex of cobalt-exchanged zeolite A. However, the oxygen atoms are either undergoing considerable thermal motion or are disordered over several off-axis locations. The Ca-C distance is 2.83A˚. Inside the β-cage, with site occupancy approximately three-fourths, there are AlO 4H 3 tetrahedral species evenly distributed between two orientations, as has been found previously in studies of divalent exchanged samples of zeolite A. This aluminum complex bonds to the framework via Al-O-H … O(3) hydrogen bonds and there is coordination of the non-hydrogen-bearing oxygen atom to exchangeable calcium ions (Al-O … Ca).