Functional materials that respond to chemical or physical stimuli through reversible structural transformations are highly desirable for the integration into devices. Now, a new stable and flexible eightfold interpenetrated three‐dimensional (3D) metal–organic framework (MOF) is reported, [Zn(oba)(pip)]n (JUK‐8) based on 4,4′‐oxybis(benzenedicarboxylate) (oba) and 4‐pyridyl functionalized benzene‐1,3‐dicarbohydrazide (pip) linkers, featuring distinct switchability in response to guest molecules (H2O and CO2) or temperature. Single‐crystal X‐ray diffraction (SC‐XRD), combined with density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations, reveal a unique breathing mechanism involving collective motions of eight mixed‐linker diamondoid subnetworks with only minor displacements between them. The pronounced stepwise volume change of JUK‐8 during water adsorption is used to construct an electron conducting composite film for resistive humidity sensing.
Flexible metal–organic
frameworks (MOFs) are promising materials
in gas-related technologies. Adjusting the material to processes requires
understanding of the flexibility mechanism and its influence on the
adsorption properties. Herein, we present the mechanistic understanding
of CO
2
-induced pore-opening transitions of the water-stable
MOF
JUK-8
([Zn(oba)(pip)]
n
, oba
2–
= 4,4′-oxybis(benzenedicarboxylate),
pip = 4-pyridyl-functionalized benzene-1,3-dicarbohydrazide) as well
as its potential applicability in gas purification. Detailed insights
into the global structural transformation and subtle local MOF–adsorbate
interactions are obtained by three
in situ
techniques
(XRD, IR, and
13
CO
2
-NMR). These results are
further supported by single-crystal X-ray diffraction (SC-XRD) analysis
of the solvated and guest-free phases. High selectivity toward carbon
dioxide derived from the single-gas adsorption experiments of CO
2
(195 and 298 K), Ar (84 K), O
2
(90 K)
,
N
2
(77 K), and CH
4
(298 K) is confirmed by
high-pressure coadsorption experiments of the CO
2
/CH
4
(75:25 v/v) mixture at different temperatures (288, 293,
and 298 K) and
in situ
NMR studies of the coadsorption
of
13
CO
2
/
13
CH
4
(50:50
v/v; 195 K).
A new layered mixed-linker metal-organic framework [Zn(iso)(pcih)] (MOF) built from isophthalate ions (iso) and 4-pyridinecarbaldehyde isonicotinoyl hydrazone (pcih) was prepared using both solution and mechanochemical methods. By use of the latter, the 2D MOF is obtained either in a one-mortar three-component grinding or on the way of a two-step mechanosynthesis. Tuning of mechanochemical synthetic conditions allowed us to identify both necessary and favorable factors for the solid-state formation of the MOF. Single-crystal X-ray diffraction reveals the presence of interdigitated layers in the ABAB arrangement and interlayer 0D cavities filled with guest molecules. Upon thermal activation, the dynamic framework exhibits stepwise and selective adsorption of CO over N as well as high-pressure H adsorption reaching maximum excess of 1.15 wt% at 77 K. The mechanochemical synthetic protocol is expanded to a few other interdigitated structures.
New mixed-linker metal-organic framework (MOF) materials incorporating both carboxylate and hydrazone linkers were prepared. The zinc-based 3D MOFs were obtained by utilizing a presynthesized aroylhydrazone [4-pyridinecarbaldehyde isonicotinoyl hydrazone (PCIH)] and para-dicarboxylic acids [1,4-benzenedicarboxylic acid (H 2 BDC) and 4,4′-biphenyldicarboxylic acid (H 2 BPDC)]. Single-crystal X-ray diffraction revealed the interpenetrated, pillar-layered structures of the MOFs, including
A series
of mixed-linker metal–organic frameworks [Zn2(Xiso)2(pcih)2]
n
containing
substituted isophthalate linkers (Xiso2–; X = OH
or CH3 or NH2 or H) and 4-pyridinecarbaldehyde
isonicotinoyl hydrazone pillars (pcih) have been prepared by using
both solution and mechanochemical methods. Single-crystal X-ray diffraction
reveals their interdigitated two-dimensional structures with different
arrangements of layers, dependent on hydrogen bonding and CH···π
interactions involving the substituents and/or linkers. These supramolecular
interactions are responsible for the formation of interlayer pores
of various volumes, shapes, and dimensionality. All materials exhibit
selective gas adsorption of CO2 over N2 with
diverse profiles. Polar groups (OH and NH2) of the isophthalate
linkers increase chemical affinity to carbon dioxide as well as hydrolytic
and thermal stability of the frameworks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.