Amidst escalating global concerns over rising atmospheric CO2 levels, the capture and effective utilization of C1 and C2+ sources are crucial not only for advancing a sustainable society but also for economically viable chemical synthesis. CO2 valorisation as a chemical feedstock has garnered significant attention, driving the development of diverse catalytic systems and reaction pathways. Among them, single-atom catalysts (SACs) have emerged as a transformative class of materials owing to their maximized atom efficiency, well-defined active sites, and tunable electronic structures, enabling high catalytic selectivity and activity. When hosted on covalent–organic frameworks (COFs) and metal–organic frameworks (MOFs), SACs benefit from the structural regularity, high surface area, and chemical modularity of these porous crystalline scaffolds, further enhancing their catalytic performance and stability. This review provides an in–depth discussion of COF and MOF derived SACs for CO2 valorisation through electrochemical, photochemical, and thermochemical approaches. We have explored the key factors that influence the performance of the CO2 reduction reaction (CO2RR) to enhance both selectivity and efficiency. In addition to catalyst preparation and synthetic applications, we provide an in–depth analysis of the mechanistic aspects and theoretical simulations of the COF and MOF SACs based CO2 utilization. We explore the role of machine learning models in advancing SACs based CO2 valorisation. We also identify key challenges including SAC agglomeration, mechanistic ambiguity, selectivity control and limited long term operational stability, while discussing future perspectives (such as electronic structure tuning, multi atom site design, and machine learning–assisted catalyst discovery) in this field of broad scientific, technological and societal interest.