Vinyl trimethoxysilane (VTMS)-modified hexagonal mesoporous silica (HMS-3) has been synthesized at varied loading concentrations of VTMS to determine the effect of VTMS loading on hydrogen adsorption capacity. Materials were synthesized with 0, 10, 20, and 31.5 mol percent starting VTMS with respect to total silica precursor. In the modified VTMS(X)-HMS-3 silica submicron particles (X = 0%, 10%, 20%, and 31.5%), hydrogen adsorption capacity increased with a maximum of 0.72 wt% adsorbed by VTMS(31.5)-HMS-3 at 77.3 K and 825 mmHg. This adsorption surpass the adsorption capacity of the unmodified VTMS(0)-HMS-3, which attained 0.50 wt% adsorption at the same temperature and pressure. The correlative increasing trend in adsorption capacity following increased organic modification provides inspiration for similar modifications to periodic mesoporous organosilicas (PMO), which exhibit higher adsorption capacity than traditionally modified particles. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.