Trimetallic clusters in the sumanene bowl for dinitrogen activation.

It is of great importance to find catalysts for the nitrogen reduction reaction (NRR) with high stability and reactivity. A series of M 3 clusters (M = Ti, Zr, V, and Nb) supported on sumanene (C 21 H 12 ) were designed as potential catalysts for the NRR by taking advantage of the high reactivity of trimetallic clusters and the unique geometric and electronic properties of sumanene, a bowl-like organic molecule. Detailed mechanisms of NN bond cleavage on C 21 H 12 -M 3 were investigated by DFT calculations and compared with those on bare M 3 clusters. M 3 in the sumanene bowl is very stable with large binding energies, which prohibits the cohesion of M 3 into M 6 . In the bowl, M 3 has a (quasi-) equilateral triangle structure with lengthened M-M bonds, which is particularly beneficial to the N 2 transfer process on Ti 3 and V 3 clusters. The N-N bond can be dissociated by both M 3 and C 21 H 12 -M 3 clusters without the overall energy barriers. A blurring effect is found in which some geometric and electronic properties of different metal types become similar when M 3 is supported on the substrate. Our work demonstrates that sumanene is a suitable substrate to support M 3 in the activation of N 2 with enhanced stability and maintained a high level of reactivity compared to bare M 3 .