An Ultra‐Stable Cr–Hydroxamate Metal–Organic Framework From Postsynthetic Transmetalation

ABSTRACT Hydroxamate‐based metal–organic frameworks (MOFs) have attracted increasing interest due to their strong chelating ability and inherent chemical robustness; however, their stability has yet to rival that of conventional carboxylate‐based MOFs. Herein, using a tris‐hydroxamic acid linker (H 3 TATPHA), we report a family of isostructural MOFs (SUM‐86) incorporating Ga(III), In(III), and Fe(III) with a two‐fold interpenetrated srs topology. Remarkably, nearly quantitative transmetalation of SUM‐86(In) with Cr(III) affords SUM‐86(Cr) in a single‐crystal‐to‐single‐crystal manner, preserving framework topology and morphology. Benefiting from the inert coordination chemistry of Cr(III) and strong hydroxamate chelation, SUM‐86(Cr) exhibits exceptional chemical stability, retaining crystallinity in boiling water and in highly corrosive aqueous solutions, including 3 M HCl and 5 M NaOH. Moreover, SUM‐86(Cr) shows rapid and high‐capacity iodine adsorption from solution. This work establishes an effective strategy for accessing ultra‐stable hydroxamate‐based MOFs and highlights postsynthetic transmetalation as a powerful approach for framework fine‐tuning and stability enhancement.