<p>Geopolymers are inorganic aluminosilicate networks formed through alkali or acid activation of precursor materials and have emerged as promising candidates for sustainable environmental remediation. Their cross-linked three-dimensional framework, tunable porosity, and negatively charged network structure provide versatile platforms for contaminant adsorption. However, conventional geopolymer sorbents often exhibit limited selectivity in complex wastewater systems due to predominantly non-specific ion-exchange and electrostatic interactions. This review highlights recent advances in the molecular and structural engineering of functionalized geopolymer networks and hybrid adsorbent composites aimed at enhancing selective adsorption. Strategies such as surface grafting of organic ligands, incorporation of functional polymer chains, compositional tuning of aluminosilicate frameworks, and development of hybrid composites with biopolymers, conductive polymers, magnetic phases, and carbon nanostructures are critically discussed. Emphasis is placed on structure–function relationships governing adsorption behavior and selective removal mechanisms, including ion exchange, electrostatic attraction, surface complexation, coordination interactions, chelation, and affinity-driven binding toward target contaminants. Reported adsorption capacities, selectivity coefficients, regeneration performance, and stability in multicomponent systems are comparatively evaluated. Current limitations related to competitive adsorption, large-scale implementation, and long-term operational stability are also discussed. By integrating concepts from inorganic polymer chemistry and hybrid materials design, this review outlines key strategies for transforming geopolymers from non-selective ion exchangers into advanced functional sorbents for selective wastewater treatment.</p>