Carbamate formation in green-plants through the RuBisCO enzyme continuously plays a pivotal role in the conversion of CO2 from the atmosphere into biomass. With this in mind, carbamate formation from CO2 by a lanthanide source in the presence of a secondary amine is herein explored leading to a lanthanide–carbamate cage with the formula [Dy4(O2CNiPr2)12]. Magnetic studies show slow relaxation leading to the observation of hysteresis loops; the tetranuclear cage being a single molecule magnet. Detailed interpretation of the data reveals: (i) the presence of two different exchange interactions, ferromagnetic and antiferromagnetic and (ii) the observation of exchange-bias quantum tunnelling with two distinct sets of loops, attributable to ferromagnetic interactions between dysprosium ions at longer distances and antiferromagnetic exchange between dysprosium ions at shorter distances. The results clearly demonstrate that the [Dy4(O2CNiPr2)12] cage acts as a quantum magnet which in turn could be at the heart of hybrid spintronic devices after having implemented CO2 as a feedstock.