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CCIQS-1: A Dynamic Metal–Organic Framework with Selective Guest-Triggered Porosity Switching

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posted on 30.12.2021, 15:08 authored by Miriam de J. Velásquez-Hernández, Valeria B. López-Cervantes, Eva Martínez-Ahumada, Min Tu, Uvaldo Hernández-Balderas, Diego Martínez-Otero, Daryl R. Williams, Vladimir Martis, Elí Sánchez-González, Jong-San Chang, Ji Sun Lee, Jorge Balmaseda, Rob Ameloot, Ilich A. Ibarra, Vojtech Jancik
The synergy between porosity and soft properties in metal–organic frameworks (MOFs) can result in materials with adaptability of the pore size/shape to the adsorbate. Herein, we present a new guest-responsive flexible MOF: CCIQS-1. This material consists of threefold interpenetrated subnetworks comprising [Sc33-O)­(H2O)2(OH)­(μ-O2CR)6] nodes interconnected by 4,4′-(9,10-anthracenediyl)­dibenzoate ligands. This arrangement gives rise to the formation of hydrophilic and hydrophobic channels. Although the activated material is permanently porous, a crystal-to-crystal phase transition takes place upon solvent removal, leading to the contraction of the hydrophobic pores while 1D hydrophilic channels remain open. As a result, CCIQS-1 exhibits a higher affinity for guests with moderate polarity [tetrahydrofuran (THF), MeOH, and acetone] than for non-polar ones (toluene, cyclohexene, and hexane). X-ray diffraction studies on the contracted-pore phase (cp-CCIQS-1) after exposure to different solvents indicate that only adsorbates with a suitable polarity and molecular size trigger the recovery of the open-pore phase (op-CCIQS-1) via the combination of a breathing effect and subnetwork displacement.