This study introduces a new organometallic Mg(II)Co(II) catalyst for the ring-opening copolymerization (ROCOP) of carbon dioxide (CO₂) with cyclic epoxides, enabling the production of high molar mass polycarbonates. The catalyst exhibits high productivity, low loading tolerance, and excellent polymerization control, yielding polycarbonates with number average molecular weights (Mₙ) ranging from 4 to 130 kg mol⁻¹, characterized by narrow, monomodal distributions. The resulting materials, including poly(cyclohexene carbonate) (PCHC), poly(vinyl-cyclohexene carbonate) (PvCHC), poly(ethyl-cyclohexene carbonate) (PeCHC), and poly(cyclopentene carbonate) (PCPC), are amorphous thermoplastics with high glass transition temperatures (Tₚ) and thermal stability (Tₚ > 260 °C). The cyclic ring substituents influence the materials' chain entanglements, viscosity, and glass transition temperatures. PCPC shows particularly promising properties, with a 10× lower entanglement molecular weight (Mₙ)ₙ and 100× lower zero-shear viscosity compared to PCHC. All these high molecular weight polymers are fully recyclable through mechanical or chemical recycling, with PCPC exhibiting the fastest depolymerization rates, achieving an activity of 2500 h⁻¹ and >99% selectivity for cyclopentene oxide and CO₂. The study highlights the potential of CO₂-based polycarbonates as sustainable thermoplastics and the importance of catalyst development for their efficient production and recycling.This study introduces a new organometallic Mg(II)Co(II) catalyst for the ring-opening copolymerization (ROCOP) of carbon dioxide (CO₂) with cyclic epoxides, enabling the production of high molar mass polycarbonates. The catalyst exhibits high productivity, low loading tolerance, and excellent polymerization control, yielding polycarbonates with number average molecular weights (Mₙ) ranging from 4 to 130 kg mol⁻¹, characterized by narrow, monomodal distributions. The resulting materials, including poly(cyclohexene carbonate) (PCHC), poly(vinyl-cyclohexene carbonate) (PvCHC), poly(ethyl-cyclohexene carbonate) (PeCHC), and poly(cyclopentene carbonate) (PCPC), are amorphous thermoplastics with high glass transition temperatures (Tₚ) and thermal stability (Tₚ > 260 °C). The cyclic ring substituents influence the materials' chain entanglements, viscosity, and glass transition temperatures. PCPC shows particularly promising properties, with a 10× lower entanglement molecular weight (Mₙ)ₙ and 100× lower zero-shear viscosity compared to PCHC. All these high molecular weight polymers are fully recyclable through mechanical or chemical recycling, with PCPC exhibiting the fastest depolymerization rates, achieving an activity of 2500 h⁻¹ and >99% selectivity for cyclopentene oxide and CO₂. The study highlights the potential of CO₂-based polycarbonates as sustainable thermoplastics and the importance of catalyst development for their efficient production and recycling.