Synthesis and single-crystal structure of lead oxide nanoclusters in zeolite Y, |Pb 15.5 2+ (Pb4O4(Pb 16/19 2+ Pb 3/19 4+ )4)4.75|[Si117Al75O384]-FAU

Abstract

A single crystal of excessively Pb2+-exchanged zeolite Y (|Pb 15.5 2+ (Pb4O4(Pb 16/19 2+ Pb 3/19 4+ )4)4.75|[Si117Al75O384]-FAU) was prepared by exchange of Na–Y (|Na75|[Si117Al75O384]-FAU, Si/Al = 1.56) with an aqueous stream 0.05 M Pb(C2H3O2)2 at 294 K, followed by vacuum dehydration at 1 × 10−6 Torr and 693 K. Its structure was determined at 100 K, by X-ray diffraction techniques in the cubic space group Fd $$ \overline{3} $$ m and was refined to the final error indices R 1/wR 2 = 0.0639/0.1323. About 53.5 Pbn+ ions per unit cell occupy three different equipoints; 26 are at site I′, 19 are at site II, and the remaining 8.5 are at another site II. Three Pb4+ ions at some of the positions must have higher oxidation states due to elevated dehydration temperature; Pb(IIa) is supposed to coexist with Pb2+ and Pb4+ ions assuming the charge balance of the zeolite framework. A distorted Pb4O4 cube, alternating Pb2+ at Pb(I′) and O2− at O(5), coordinates with four Pb2+ and/or Pb4+ ions through its oxygen atoms to give a [Pb 4 2+ O 4 2− (Pb 16/19 2+ Pb 3/19 4+ )4]176/19+ cluster in 4.75 of eight sodalite cavities per unit cell in zeolite Y.