<p>Flue gas desulfurization (FGD) is crucial for reducing sulfur dioxide (SO₂) emissions from industrial processes, with calcium carbonate (CaCO₂)-based adsorbent widely used due to their cost-effectiveness and availability. Despite their advantages, these adsorbent face limitations such as pore blockage due to sulfation, high-temperature sintering, and limited regeneration capacity, which restrict their long-term performance. This systematic review synthesizes recent advancements in CaCO₃-based adsorbent, focusing on hybrid formulations combining metal–organic frameworks and zeolites, chemical doping, and structural modifications aimed at enhancing adsorption efficiency, stability, and regeneration. Machine learning has also emerged as a promising tool for real-time optimisation of FGD processes. Furthermore, advanced characterization techniques such as SEM, XRD, TGA, and FTIR have provided deeper insights into the degradation and regeneration mechanisms of adsorbent. Despite these innovations, challenges such as economic viability and regulatory compliance remain barriers to large-scale adoption. This review concludes by identifying future research directions to enhance the sustainability, scalability, and industrial application of CaCO₃-based adsorbent in SO₂ removal.</p>