The need to meet our energy and resource needs while limiting detrimental impacts on climate and environment motivate efforts to harness subsurface geologic environments for fluid recovery and storage. However, the subsurface environments are characterized by a wide range of chemical and physical heterogeneities that can influence the properties of thermodynamics, flow, and reactivity in these formations which can limit our ability to develop predictive controls over the fate of injected fluids such as carbon dioxide. Significant knowledge gaps exist in our understanding of the chemical and morphological evolution of materials at relevant subsurface conditions and the reactivity of fluids at solid interfaces. It is now possible to address this challenge due to advances in cross-scale synchrotron-based advanced characterization approaches and our ability to architect materials that are analogous to natural occurring minerals.In this thesis, fundamental insights into the assembly of siliceous materials and alumino-silicates using operando X-ray scattering measurements are discussed. The role of silica in inducing hydrogel formation for enhancing permeability in subsurface environments and the influence of quartz interfaces on directing the assembly of surfactants are investigated. The influence of amorphous silica dissolution and reprecipitation on the non-monotonic evolution of porosity in silica-rich shales and the role of siliceous nanochannels in directing the formation of stable calcium carbonate are elucidated. Approaches to determine interfacial reactivity involving alumino-silicates (e.g., sodium montmorillonite) and water using scattering and spectroscopy measurements and the alignment with predictions from reactive molecular dynamics simulations are discussed. These studies shed fundamental insights into the basic science underlying the reactivity of siliceous materials in diverse subsurface environments