Geopolymers (GP) represent a fascinating alternative to typical structural ceramics, but all prior work has demonstrated substantial mesoporosity. This porosity is detrimental to mechanical properties as well as drying failure resistance. Here, mesoporosity in metakaolin Na-based GP has been reduced by an order of magnitude through the addition of acrylate-functional silane coupling agents, and the effect of this modification was extensively analyzed using a variety of characterization techniques. It was found that a critical concentration of approximately 0.06 mol methacryloxypropyltrimethoxysilane/mol GP was necessary for extensive property modification. Above this concentration, membranes and tubes of organic material could be observed, suggesting that only this surplus additive contributed to mesoporosity reduction. The source of this mesoporosity reduction is shown to be segregation of free water via hydrogel-like interaction caused by the formation of sodium acrylate groups.