Design and synthesis of pillared metal–organic frameworks featuring olefinic fragments

While metal–organic frameworks (MOFs) are known primarily for their well-defined crystalline porous structures that make them desirable for a myriad of applications, they also distinguish themselves with their chemical tunability. One strategy for chemical tailoring of MOF structures is post-synthetic modification (PSM) targeting moieties present in their organic building blocks (linkers). In this context, alkene (olefinic) fragments are underrepresented in the realm of MOFs despite their extremely well-established and versatile chemistry. With the majority of reported olefinic MOFs falling into the microporous regime, the PSM opportunities involving bulkier reagents are severely limited. Herein, we report a family of UofT (University of Toronto) pillared MOFs constructed around olefinic 1,4-bis(2-(pyridin-4-yl)vinyl)benzene (BPVB) and tetrakis(4-carboxyphenyl)porphyrin (TCPP) linkers. By utilizing a variety of M(II) [M = Zn, Ni, Co] precursors, three structurally distinct frameworks were synthesized and characterized. Most notably, the nickel-based framework represents the first reported example of a stable mesoporous olefinic pillared MOF. In addition to the de novo formation of a stable pillared MOF, Ni(II) is also used in a cation exchange process to structurally reinforce zinc-based frameworks.