In-Situ Ligand Formation-Driven Preparation of a Heterometallic Metal–Organic Framework for Highly Selective Separation of Light Hydrocarbons and Efficient Mercury Adsorption

By means of the in situ ligand formation
strategy and hard–soft acid–base (HSAB) theory, two
types of independent In­(COO)4 and Cu6S6 clusters were rationally embedded into the heterometallic metal–organic
framework (HMOF) {[(CH3)2NH2]­InCu4L4·xS}n (BUT-52). BUT-52 exhibits a three-dimensional (3D) anionic
framework structure and has sulfur decorating the dumbbell-shaped
cages with the external edges of 24 and 14 Å by the internal
edges. Remarkably, because of the stronger charge-induced interactions
between the charged MOF skeleton and the easily polarized C2 hydrocarbons (C2s), BUT-52 was used for C2s over CH4 and shows both high adsorption heats of C2s and selective separation abilities for C2s/CH4. Furthermore, BUT-52 also displays efficient mercury adsorption
resulting from the stronger-binding ability beween the sulfur and
the mercury and can remove 92% mercury from methanol solution even
with the initial concentration as low as 100 mg/L. The results in
this work indicate the feasibility of BUT-52 for the separation of
light hydrocarbons and efficient adsorption/removal of mercury.