Hydration and Hydrolysis of Boron-Substituted Aluminophosphate BAPO-5 According to Solid-State NMR and DFT Calculations

Abstract

Microporous aluminophosphates (AlPOs) are prospective materials that can be used as molecular sieves and adsorbents in their pure form or catalysts and catalyst supports when some of the sites are substituted with heteroatoms. One of the approaches to create and finely tune Brønsted acid sites in AlPO is simultaneous introduction of Si and B into the framework. However, boron substitution of AlPOs is briefly studied and proceeds with difficulties. Here, we apply multinuclear solid-state nuclear magnetic resonance together with DFT calculations to investigate the behavior of aluminophosphate AlPO-5 and its boron-substituted analogue BAPO-5 upon interaction with water. We demonstrate that the structure of AlPO-5 facilitates a homogeneous distribution of water molecules and makes BAPO-5 less susceptible to hydrolysis compared to microporous AlPO-11 and BAPO-11.