Partial Order–Disorder Transformation of Interpenetrated Porous Coordination Polymers

Abstract

Controlling interpenetration and flexibility behaviors is intriguing and fundamental for porous coordination polymers. We report exceptional interpenetration behaviors involving controllable partial order-disorder structural transformations. A new bis-benzotriazolate ligand (NaH 2 sbbta) with a twisted and anionic backbone was designed and synthesized. Solvothermal reaction of ZnCl 2 and NaH 2 sbbta yielded (Et 2 NH 2 ) 3 [Zn 5 Cl 4 (sbbta) 3 ]•6DEF (2) possessing 2-fold interpenetrated anionic pcu networks with symmetry, shape, and charge different with the known analogues. More interestingly, powder and single-crystal X-ray diffraction showed that 2 can undergo solvent-induced structural transformation to form a non-interpenetrated anionic pcu network with larger pores (1). Consequently, 1/2 can selectively adsorb/exchange cationic dyes from neutral and anionic dyes with tunable size selectivity. However, since the transformations are reversible without obvious change of crystal sizes, the network disappeared in X-ray crystallography should be mainly disordered rather than decomposed. Further, the structural transformations can be suppressed by thermal decomposition/removal of Et 2 NH 2 + /Et 2 NH. Computational simulations indicate that the ordered/disordered structures are stabilized by relatively large and small sizes of the solvent molecules.

A gating ultramicroporous metal-organic framework showing high adsorption selectivity, capacity and rate for xylene separation

“…Besides the same two-fold symmetric disorder, mX and oX further show two-fold positional disorders, giving more positional confliction probability between the guest locations, which is consistent with their lower experimental saturation adsorption amounts (Figure 3). Considering both the experimental saturation uptakes and the residual electrons in pores of the crystal structures [49], the pX, mX, and oX guest molecules in the crystal structures were constrained as 100%, 87%, and 75% of the full occupancy, respectively (Table S5).…”

Two-dimensional heterostructures built from ultrathin CeO2 nanosheet surface-coordinated and confined metal–organic frameworks with enhanced stability and catalytic performance

“…Considering all the above, we envisage that ultrathin CeO 2 would be an ideal nanomaterial to support MOFs. Besides, a Ce-decorated transition metal was reported by Zheng and co-workers, 27 and to the best of our knowledge, the heterostructures of ultrathin CeO 2 nanosheets with surface-coordinated and confined transition metal-MOFs were poorly understood until fairly recently.…”

On the Role of Flexibility for Adsorptive Separation

“…TCF and guest-driven flexibility do not always occur in a crystal-to-crystal manner. Many flexible MOFs can show reversible crystal-to-amorphous transformations, and some crystal-to-crystal transformations involve partially disordered/amorphous regions. , As indicated by the nonideal isotherm shapes (not infinitely large slope at the inflection point), crystal-to-crystal structural transformations are generally not completely periodic/cooperative. The host framework can adopt more complicated periodic/aperiodic intermediate structures during the transformation, especially at nonstoichiometric guest loadings .…”