Abstract :  The organocatalytic coupling of oxetanes and carbon dioxide (CO₂) offers a sustainable route to poly(trimethylene carbonate)s and/or functional 6-membered cyclic carbonate monomers. This transformation is more challenging than when using more strained epoxide comonomers and even more so when it is performed using sustainable metal-free routes. Herein, we report a mild, organocatalytic oxetane/CO₂ coupling procedure that enables the selection of cyclic carbonate or polymer from a common intermediate. Using a novel I₂-based binary catalyst system, cyclic carbonate with high selectivity (up to 94%) was obtained at 55 °C whereas simply changing the temperature to 105 °C yielded the polycarbonate with M_n up to 6.4 kDa thus showing that either trimethylene carbonate or its concomitant polycarbonate product can be selected solely by manipulation of the reaction conditions.