In this study, we present the preparation and application of a new manganoporphyrin Hf-MOF catalyst, Hf-PCN-222(Mn) for the direct oxidative carboxylation of alkenes with CO₂, leading to the effective formation of cyclic organic carbonates (COCs). In contrast to the conventional two-step process, this one-step methodology eliminates the need for the preparation, purification, and handling of epoxides. Hf-PCN-222(Mn) operates under very mild conditions, enabling the synthesis of a wide variety of COCs from alkenes (23 examples, up to 75% yield), as well as the chemoselective and size-selective carboxylation of dienes (7 examples, up to 61% yield). Additionally, we observed that Hf-PCN-222(Mn) could be recycled multiple times without significant loss of activity, providing insight into the sustainability of this approach.