Acquiring an effective CaO-based CO 2 sorbent and achieving selective methanation of CO 2 .

CO 2 capture, utilization, and storage are promising strategies to solving the problems of superfluous CO 2 or energy shortage. Here, mechanochemical reduction of CO 2 by a MgH 2 /CaH 2 mixture was first performed, by which we achieve selective methanation of CO 2 and acquire an effective CaO-based CO 2 sorbent, simultaneously. The selectivity of methanation is near 100% and the yield of CH 4 reaches 30%. Four MgO and carbon-doped CaO-based CO 2 sorbents (MgO/CaO/C, MgO/2CaO/C, MgO/4CaO/C, and MgO/8CaO/C) were formed as solid products in these reactions. Among them, the MgO/4CaO/C sorbent shows high initial adsorption amount of 59.3 wt% and low average activity loss of 1.6% after 30 cycles. This work provides a novel, well-scalable, and sustainable approach to prepare an efficient inert additive-including CaO-based CO 2 sorbent and selectively convert CO 2 to CH 4 at the same time.