Addition of ethylene to a π-conjugated two-dimensional nickel-based organometallic framework with implications for olefin separation.

We have investigated the mechanism for the reversible addition of ethylene to a periodic 2D network of square-planar nickel centers ([Ni(SC)4]n) using density functional theory. The mechanism is analogous to that for homogeneous olefin binding to metal bis(dithiolene) complexes. We considered periodic boundary calculations (PBC) as well as clusters containing up to 12 nickel atoms using a screened hybrid density functional to obtain accurate reaction barriers. Several different products were analyzed. The lowest-energy route begins with the addition of ethylene across the nickel-sulfur bond, which has previously not been considered for this system. The effect of the addition of several alkene molecules simultaneously on the surface was investigated to determine the potential efficiency of this material. This material is a candidate for alkene purification as it exhibits similar reactivity to its molecular analog in terms of the relative stability of products, energy barriers, and molecular efficiency while also providing the intrinsic technical benefits of heterogeneous catalysis.