A General Correlation for the ¹²⁹Xe NMR Chemical Shift−Pore Size Relationship in Porous Silica-Based Materials

Abstract

A general correlation for the 129Xe NMR chemical shift−pore size relationship (δ versus D) in porous silica-based materials over the range 0.5−40 nm has been demonstrated: δ = δs/(1 + D/b), with δs = 116 ± 3 ppm and b = 117 ± 8 Å for the 34 materials studied. The correlation may be used in the characterization of silica samples with unknown pore structure. Even within this general correlation, subsets of materials of similar origin display finer correlations that indicate an acute sensitivity to details of the pore surfaces.