The structure of a carbon monoxide adduct of cobalt-exchanged zeolite A (Co 5.25Na 1.5A · 1.5CO) by neutron profile refinement

Abstract

The structure of a carbon monoxide adduct of cobalt-exchanged zeolite A, CO 5.25Na 1.5A · 1.5CO, has been determined by Rietveld neutron profile refinement. The space group used was Fm 3c with a = 24.1557(14) Å; the final R pw was 13.8%. All exchangeable cations are located in sites adjacent to the 6-rings; 3.75 of the cobalt cations sit 0.4 Å inside the β-cage (Co(2)) and are arranged tetrahedrally about the eight 6-ring sites in the β-cage. The sodium cations (Na(1)) reside just inside the α-cage in sites similar to those found previously for zeolites 3A, 4A, and 5A. The remaining 1.5 cobalt cations (Co(1)) are located in sites similar to those for sodium, but they are also coordinated to the carbon monoxide molecules, which lie on, or close-to, the threefold axis which passes through the 6-ring. Inside the β-cage there is a tetrahedral aluminum complex of AlO 4 type, the oxygen atoms (O∗) of which point toward six rings not occupied by cobalt cations, Co(2). Each of the oxygen atoms of this complex is involved in a hydrogen bond (2.83 Å) to the 6-ring oxygen O(3). Approximately 2 3 of these bonds are of type O∗H···O(3) and 1 3 of type O∗···HO(3).