Metal Organic Framework-Derived Iron Catalysts for the Direct Hydrogenation of CO₂ to Short Chain Olefins

We report the synthesis of a highly active, selective, and stable catalyst for the hydrogenation of CO 2 to short chain olefins in one single step by using a metal organic framework as catalyst precursor. By studying the promotion of the resulting Fe(41 wt %)-carbon composites with different elements (Cu, Mo, Li, Na, K, Mg, Ca, Zn, Ni, Co, Mn, Fe, Pt, and Rh), we have found that only K is able to enhance olefin selectivity. Further catalyst optimization in terms of promoter loading results in catalysts displaying unprecedented C 2 –C 4 olefin space time yields of 33.6 mmol·gcat –1 ·h –1 at X CO 2 = 40%, 320 °C, 30 bar, H 2 /CO 2 = 3, and 24 000 mL·g –1 ·h –1 . Extensive characterization demonstrates that K promotion affects catalytic performance by (i) promoting a good balance between the different Fe active phases playing a role in CO 2 hydrogenation, namely, iron oxide and iron carbides and by (ii) increasing CO 2 and CO uptake while decreasing H 2 affinity, interactions responsible for boosting olefin selectivity.