Integrated theoretical and empirical studies for probing substrate-framework interactions in hierarchical catalysts

Soft-templating with siliceous surfactant is an established protocol for the synthesis of hierarchically-porous silicoaluminophosphates (HP SAPOs) with improvedmass transport properties.Motivated by the enhanced performance of HP SAPOs in the Beckmann rearrangementof cyclohexanone oxime to the nylon-6 precursor, ε-caprolactam, we have undertakenan integrated theoretical and empirical studyto investigate thecatalytic potential of thesiliceous mesopore network.Neutron scattering studies, in particular, have provided unique insight into the substrate-framework interactions in HP (Si)AlPOs, allowing reactive species to be studied independent of the catalyst matrix.The spectroscopic (INS, FTIR, MAS NMR) and computational analyses reveal that inthe organosilane-templated SAPO, the interconnectivity of micro-and meso-pores permits a cooperativity between their respective silanol and Brønsted acid sitesthat facilitates the protonation of cyclohexanone oxime in a physical mixture, at ambient temperature.