Using InCl Vapor to Ion Exchange Indium into Zeolite Na–X. Single Crystal Structure of |In34Na50|[Si100Al92O384]–FAU Containing In57+ and In+
journal contributionposted on 12.07.2012, 00:00 by Dipak Sen, Nam Ho Heo, Karl Seff
Indium ions were introduced into zeolite X (FAU, Si/Al = 1.09) by anhydrous vapor-phase ion exchange (VPIE). In14+(In57+)4Na50+–X (approximate formula) was prepared by the reaction of fully dehydrated Na92+–X with 13 Torr of InCl(g) at T = 673 K. Its structure was determined using single-crystal crystallography with synchrotron X-radiation and was refined in the space group Fd3̅ (a = 24.996(1) Å) with all 1566 unique data; the final error index R1 is 0.076. InCl(g) reacted with about 46% of the Na+ ions in the zeolite, to give In57+ (centered tetrahedral, In–In = 2.684(7) Å) and In+ cations. In57+ centers exactly half of the sodalite cavities, strongly suggesting alternating occupancy; each terminal atom (at site I′) bonds to three framework oxygen atoms of a double 6-ring (In–O = 2.248(6) Å and O–In–O = 102.2(2)°). The In+ ions occupy four crystallographically distinct cationic sites: 5.8(3) per unit cell are in the sodalite cavities (site I′), 2.7(7) are near single 6-rings in the supercage (site II), 2.6(4) are near triple 4-rings in the supercage (site III′), and 3.1(5) are at second III′ site. About half of the Na+ ions complete the filling of the single 6-rings; the remainder are at 12-ring sites. Most In+ ions are easily approachable by guest molecules through the zeolite's 12-ring channel system.