Atomic layer deposition (ALD) of Ni on the metal–organic framework NU-1000 has been shown to generate a material that serves as a catalyst for ethylene dimerization. However, the precise nature of the active catalytic site or sites remains uncertain. Here we employ periodic density functional calculations to characterize the structure and reactivity of the deposited species. Optimized lattice constants for a sequence of structures incorporating successively more Ni₄-hydroxo clusters in the c pore of NU-1000 show good agreement with experimental trends involving multiple ALD cycles; therefore we study the catalytic cycle for this cluster in detail, and we compare it to that for a site with only a single Ni atom. We find that both the atomic Ni catalyst and the Ni₄-hydroxo cluster have higher catalytic activity in the singlet state than in the triplet state. We also find that the two catalysts have very similar activity. Thus, precise size control of the active catalytic species is not essential for ethylene dimerization in this system.

镍在金属-有机骨架NU-1000上的原子层沉积（ALD）已被证明可产生用作乙烯二聚化催化剂的材料。然而，一个或多个活性催化位点的确切性质仍然不确定。在这里，我们采用周期性密度泛函计算来表征沉积物质的结构和反应性。在NU-1000的C孔中相继结合更多Ni _4-羟基簇的结构序列的优化晶格常数与涉及多个ALD循环的实验趋势显示出良好的一致性。因此，我们将详细研究该簇的催化循环，并将其与只有一个Ni原子的位点进行比较。我们发现原子镍催化剂和镍₄-羟基簇在单重态比在三重态具有更高的催化活性。我们还发现两种催化剂具有非常相似的活性。因此，对于该系统中的乙烯二聚作用，活性催化物质的精确尺寸控制不是必不可少的。