Linker Expansion and Its Impact on Switchability in Pillared-Layer MOFs

Abstract

Linker elongation is an important method to systematically adjust porosity and pore size in isoreticular MOFs. In flexible structures, this approach opens the possibility for the systematic analysis of the building blocks and their contribution to the overall flexible behavior enabling tuning of the framework responsivity toward molecular stimuli. In this work, we report two new compounds isoreticular to the highly flexible pillared layer structure DUT-8­(Ni) ([Ni2(2,6-ndc)2(dabco)] n , 2,6-ndc = 2,6-naph­thalene­di­carboxylate, dabco = 1,4-diaza­bicylo­[2.2.2]­octane). Aromatic linker 2,6-ndc was substituted by longer carboxylic linkers, namely, 4,4′-bi­phenyl­di­carboxylate (4,4′-bpdc) and 4,4′-stil­bene­di­carboxylate (4,4′-sdc), while the dabco pillar was retained. The structural response of the new compounds toward the desolvation and adsorption of various fluids was studied using advanced in situ PXRD techniques, demonstrating distinct differences in the flexible behavior of three compounds and disclosing the impact of linker structure on the framework response. Theoretical calculations provide mechanistic insights and an energetic rationale for the pronounced differences in switchability observed. The energetics of linker bending and linker–linker dispersion interactions govern the phase transitions in investigated MOFs.

Continuous Breathing Rare-Earth MOFs Based on Hexanuclear Clusters with Gas Trapping Properties

“…In contrast to the significant progress in the design and discovery of rigid, highly porous MOFs with fascinating structures based on different topologies following the reticular chemistry approach, − a rational design of flexible MOFs is currently restricted in few isostructural series including MIL-53, MIL-88, MCF-18, DUT-49, and paddlewheel-based, pillared structures. ,− This is because framework flexibility is far more difficult to be realized due to the synergistic and cooperation effect between different types and strengths of interactions, including coordination bonds, intra- and intermolecular forces, host–guest interactions, crystal size and morphology. − Control over these complex and synergistic interactions requires the synthesis and characterization of new flexible MOFs with diverse chemical and structural composition from which important structure–property relationships can be extracted. − …”

One Atom Can Make All the Difference: Gas-Induced Phase Transformations in Bisimidazole-Linked Diamondoid Coordination Networks

“…Ligand functionalization has been shown to transform isotherm types from rigid to flexible by addition of flexible pendant groups on the framework, or by substituting hydrogen atoms with halogen atoms or other functional groups. , Additionally, halogen atom substitution or addition of functional groups on the linker has been observed to alter the gate-opening pressure values. Ligand extension has been used to modify isotherm types, and ligand substitution has been reported to shift gate-opening pressure values depending on the rotational freedom of the ligand. Apart from composition, sorption profiles can also be affected by the crystal size, − crystal defects, − repeated cycling, sample pretreatment, − and temperature …”

Molecular Dynamics Simulations of the Breathing Phase Transition of MOF Nanocrystallites II: Explicitly Modeling the Pressure Medium

“…For this purpose, the same model system, DMOF-1 [Zn 2 (bdc) 2 (dabco); bdc: 1,4-benzenedicarboxylate; dabco: 1,4-diazabicyclo(2.2.2)octane] ( Dybtsev et al, 2004 ) is chosen. In addition, NCs of the MOFs DUT-8(Cu) [Cu 2 (2,6-ndc) 2 (dabco); DUT: Dresden University of Technology; 2,6-ndc: 2,6-naphthalenedicarboxylate] ( Klein et al, 2010 ), and DUT-128(Zn) [Zn 2 (4,4′-bpdc) 2 (dabco); 4,4′-bpdc: 4,4′-biphenyldicarboxylate] ( Bönisch et al, 2021 ) are investigated in order to reveal the effect of a different linker group on the process of pore closing (see Figure 1 ).…”