Sequence control of metals in MOF by coordination number precoding for electrocatalytic oxygen evolution

Inorganic porous materials are prevailing in energy storage, environment remediation, and catalysis; however, it is attractive to control the spatial arrangement of heterometals in these materials with atomic accuracy. Here, we report the precise positioning of metals with identical valence, coordination number, and similar size, such as Zn (II) and Co (II), to generate an alternating sequence in a multivariate (MTV) metal-organic framework (MOF), ZnCo-MTV-MOF-699, with a rare sheet secondary building unit. This is achieved by precoding their coordination number in a parent MOF, ZnCo-MOF-69C, followed by single-crystal-to-single-crystal transformation, where the entire process is monitored in situ by time-resolved small-angle X-ray scattering. Coordination number precoding of other metal pairs, Zn-Ni and Zn-Cu, in MTV-MOFs is also obtained. The sequence-coded MTV-MOF exhibits a much lower overpotential than that of the non-coded counterpart in oxygen evolution reaction, unveiling the power of metal sequence control.