Crystal structure and X-ray luminescence of zeolite Y (Si/Al = 1.69) containing extraframework hafnium(IV)

Hafnium(IV) was introduced into zeolite Y by allowing anhydrous Cs,Na–Y (|Cs₄₃Na₂₈|[Si₁₂₁Al₇₁O₃₈₄]-FAU) to react with HfCl₄ (g, 3.2 × 10³ Pa) at 503 K for 48 h. The crystal structures of Cs,Na–Y and of the product, Hf,Cl,Cs,Na–Y (|(HfCl)_1.5(NaCl)_4.5Cs₄₃Na_23.5|[Si₁₂₁Al₇₁O₃₈₄]-FAU), were determined by single-crystal crystallography at 293 K using synchrotron X-radiation. They were refined in the space group Fd3‾m (a = 24.808(1) Å and 24.735(1) Å) with all unique data to the final error indices R₁ = 0.062 and 0.067 for the 1572 and 1413 reflections for which F_o > 4σ(F_o), respectively. Their compositions were confirmed by energy-dispersive X-ray analyses. The Hf⁴⁺ ions occupy 6-rings in the supercages; each is tetrahedral with three bonds to 6-ring oxygen atoms and one to a Cl⁻ ion. Per unit cell, 4.5 Na⁺ ions do that also. The remaining Na⁺ and Cs⁺ ions occupy well established cation positions near 6- and 12-rings. The sky-blue X-ray induced luminescence spectrum of Hf,Cl,Cs,Na–Y is a broad band from 300 to 650 nm with peaks at 380 nm and 490 nm. This luminescence is blue-shifted compared to that of zeolite Hf,Cl,Cs,Na-A.