The transmetalation (the replacement of metal ions) of a family of highly porous isostructural metal−organic frameworks (MOFs), M 6 (BTB) 4 (BP) 3 (where M = Zn(II) (1), Co(II) (2), Cu(II) (3), and Ni(II) (4), BTB = 1,3,5benzenetribenzoate, and BP = 4,4′-dipyridyl) with an ith-d net topology has been investigated. These compounds have different framework stabilities depending on the framework metal ions. The transmetalation and the reverse transmetalation reactions of the framework metal ions were observed between the MOFs, 1 and 2, having a similar thermodynamic stability. While the transmetalation from thermodynamically less stable 1 and 2 to more stable 3 and 4 were achieved by soaking single crystals of 1 and 2 in a solution of N,N′-dimethylformamide (DMF) containing Cu(II) and Ni(II) ions, respectively, no reverse transmetalation was observed. By simply controlling the soaking time, not only could homogeneously transmetalated crystalline framework structures be prepared via the thermodynamically controlled complete replacement of the framework metal ions but also selectively transmetalated core−shell heterostructures were formed via kinetically controlled replacement that was mainly restricted to the external shell region of the crystal. The fully transmetalated MOFs showed significantly improved framework stabilities compared with the parent MOFs. A marked improvement in the framework stability was observed, even in the selectively transmetalated Co(II)/Cu(II)-and Co(II)/Ni(II)-core−shell heterostructures. Although the frameworks are partially transmetalated, the framework stability of not only the external shell region but also of the internal core region was significantly affected.

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A metal–organic framework (MOF) having superprotonic conductivity, MOF‐808, is prepared by modulating the binding mode of the sulfamate (SA) moieties grafted onto the metal clusters. The activation of the SA‐grafted MOF‐808 at 150 °C changes the binding mode of the grafted SA from monodentate to bridging bidentate, thus converting the neutral amido (‐S−NH2) moiety of the grafted SA to the more acidic cationic sulfiliminium (‐S=NH2+) moiety. Further, the acidic sulfiliminium moiety of MOF‐808‐4SA‐150 results in more efficient proton conduction than the amido moiety of MOF‐808‐4SA‐60. At 60 °C and 95 % relative humidity, MOF‐808‐4SA‐150 is found to have a proton conductivity of 7.89×10−2 S cm−1, which is more than 30‐times higher than that of MOF‐808‐4SA‐60. Moreover, this superprotonic conductivity is well maintained over 1000 cycles of conductivity measurements and for similar cyclic measurements each day for seven days.

Metal–organic frameworks, [Ni(HBTC)(dabco)] (2) and [Ni2(HBTC)2(bipy)0.6(dabco)1.4] (3) (where H3BTC is 1,3,5-benzenetricarboxylic acid, dabco is 1,4-diazabicyclo[2.2.2]octane, and bipy is 4,4′-bipyridine), were prepared via postsynthetic ligand exchanges of [Ni(HBTC)(bipy)] (1). By controlling the concentration of dabco, we could obtain not only entropically favorable 2 with completely exchanged dabco but also enthalpically favorable 3 with selectively exchanged bipy/dabco in the alternating layers.

MOF‐74 is one of the most explored metal–organic frameworks (MOFs), but its functionalization is limited to the dative post‐synthetic modification (PSM) of the monodentate solvent site. Owing to the nature of the organic ligand and framework structure of MOF‐74, the covalent PSM of MOF‐74 is very demanding. Herein, we report, for the first time, the covalent PSM of amine‐tagged defective Ni‐MOF‐74, which is prepared by de novo solvothermal synthesis by using aminosalicylic acid as a functionalized fragmented organic ligand. The covalent PSM of the amino group generates metal binding sites, and subsequent post‐synthetic metalation with PdII ions affords the PdII‐incorporated Ni‐MOF‐74 catalyst. This catalyst exhibits highly efficient, size‐selective, and recyclable catalytic activity for the Suzuki–Miyaura cross‐coupling reaction. This strategy is also useful for the covalent modification of amine‐tagged defective Ni2(DOBPDC), an expanded analogue of MOF‐74.