Capturing an Aluminophosphite Intermediate in the New Route of Synthesizing Zeolite-like Aluminophosphates

A new route for synthesizing zeolite-like aluminophosphates by using phosphorous acid (H3PO3) as the phosphorus source has been discovered. An important intermediate called NKX-2 has been captured in the crystallization of zeolite-like AlPO4-5. NKX-2 is a microporous aluminophosphite with one-dimensional 12-member ring channels in its structure. It is acidic-stable in HCl solution and basic-stable under hydrothermal conditions at 200 °C for 15 days. An overview of this new route has been displayed by XRD patterns on the formation of AlPO4-5 in a nonaqueous system. NKX-2 appeared first as an intermediate, and then reflections due to AlPO4-5 appeared gradually with the time evolution. The conversion of P(III) species to P(V) species in the crystallization has been detected by Raman investigation. Besides, with use of NKX-2 as the starting material, by adding organic amine to the mixture of NKX-2 and water, AlPO4-5, AlPO4-41, and MeAPO-47 aluminophosphates have also been obtained hydrothermally.