Enhanced ²⁹Si spin-lattice relaxation and observation of three dimensional lattice connectivity in zeolites by two-dimensional ²⁹Si MASS NMR

Abstract

It is shown that considerable sensitivity enhancement is achieved in the ²⁹Si MASS NMR spectra of highly siliceous zeolites by pretreating the material with oxygen. The presence of adsorbed molecular oxygen in zeolite channels promotes an efficient ²⁹Si spin lattice relaxation via a paramagnetic interaction between the lattice ²⁹Si T-site and the adxorbed oxygen on zeolite channels. This affords an efficient 2-D data collection and leads to increased sensitivity. The utility of this method is demonstrated in a two-dimensional COSY-45 NMR experiment of a high silica zeolte ZSM-5.