No abstract

Stimuli-responsive materials can respond to external effects, and proton transport is widespread and plays a key role in living systems, making stimuli-responsive proton transport in artificial materials of particular interest to researchers due to its desirable application prospects. On the basis of the rapid growth of proton-conducting porous metal–organic frameworks (MOFs), switched proton-conducting MOFs have also begun to attract attention. MOFs have advantages in crystallinity, porosity, functionalization, and structural designability, and they can facilitate the fabrication of novel switchable proton conductors and promote an understanding of the comprehensive mechanisms. In this Perspective, we highlight the current progress in the rational design and fabrication of stimuli-responsive proton-conducting MOFs and their applications. The dynamic structural change of proton transfer pathways and the role of trigger molecules are discussed to elucidate the stimuli-responsive mechanisms. Subsequently, we also discuss the challenges and propose new research opportunities for further development.

High‐purity ethanol is a promising renewable energy resource, however separating ethanol from trace amount of water is extremely challenging. Herein, two ultramicroporous MOFs (UTSA‐280 and Co‐squarate) were used as adsorbents. A prominent water adsorption and a negligible ethanol adsorption identify perfect sieving effect on both MOFs. Co‐squarate exhibits a surprising water adsorption capacity at low pressure that surpassing the reported MOFs. Single crystal X‐ray diffraction and theoretical calculations reveal that such prominent performance of Co‐squarate derives from the optimized sieving effect through pore structure adjustment. Co‐squarate with larger rhombohedral channel is suitable for zigzag water location, resulting in reinforced guest‐guest and guest‐framework interactions. Ultrapure ethanol (99.9 %) can be obtained directly by ethanol/water mixed vapor breaking through the columns packed with Co‐squarate, contributing to a potential for fuel‐grade ethanol purification.

Three novel 3D calcium-based metal–organic frameworks (FJU-67, FJU-68, and FJU-69) established on naphthalene diimide chromophores have been synthesized, which exhibit unique multiple interpenetrated networks with dia net topologies.

Porous organic materials (POMs) have shown great potential for fabricating tunable miniaturized lasers. However, most pure-POM micro/nanolasers are achieved via coordination interactions, during which strong charge exchanges inevitably destroy the intrinsic gain property and even lead to optical quenching, hindering their practical applications. Herein, we reported on an approach to realize hydrogen-bonded organic framework (HOF)-based in situ wavelength-switchable lasing based on the framework-shrinkage effect. A flexible HOF with reversible framework shrinkage was constructed from gain blocks with multiple rotors. The framework shrinkage of the HOF induced the in situ regulation on the conformation and conjugation degree of gain blocks, leading to distinct energy-level structures with blue/green-color gain emissions. Inspired by this, the in situ wavelength-switchable lasing from HOF microcrystals was achieved through reversibly controlling the framework shrinkage via the absorption/desorption of guests. The results offer useful insight into the use of flexible HOFs for exploiting miniaturized lasers with on-demand nanophotonics performance.

Rational design of hydrogen‐bonded organic frameworks (HOFs) with multiple functionalities is highly sought after but challenging. Herein, we report a multifunctional HOF (HOF‐FJU‐2) built from 4,4′,4′′,4′′′‐(9H‐carbazole‐1,3,6,8‐tetrayl)tetrabenzaldehyde molecule with tetrabenzaldeyde for their H bonding interactions and carbazole N−H site for its specific recognition of small molecules. The Lewis acid N−H sites allow HOF‐FJU‐2 facilely separate acetone from its mixture with another solvent like methanol with smaller pKa value. The donor (D)‐π‐acceptor (A) aromatic nature of the organic building molecule endows this HOF with solvent dependent luminescent/chromic properties, so the column acetone/methanol separation on HOF‐FJU‐2 can be readily visualized.

Rational design of high nuclear copper clusterbased metal-organic frameworks has not been established yet. Herein, we report a novel MOF (FJU-112) with the ten-connected tetranuclear copper cluster [Cu 4 -(PO 3 ) 2 (μ 2 -H 2 O) 2 (CO 2 ) 4 ] as the node which was capped by the deprotonated organic ligand of H 4 L (3,5-Dicarboxyphenylphosphonic acid). With BPE (1,2-Bis(4-pyridyl)ethane) as the pore partitioner, the pore spaces in the structure of FJU-112 were divided into several smaller cages and smaller windows for efficient gas adsorption and separation. FJU-112 exhibits a high separation performance for the C 2 H 2 /CO 2 separation, which were established by the temperature-dependent sorption isotherms and further confirmed by the labscale dynamic breakthrough experiments. The grand canonical Monte Carlo simulations (GCMC) studies show that its high C 2 H 2 /CO 2 separation performance is contributed to the strong π-complexation interactions between the C 2 H 2 molecules and framework pore surfaces, leading to its more C 2 H 2 uptakes over CO 2 molecules.

The separation of C2H2/CO2 is not only industrially important for acetylene purification but also great scientific challenge due to their very similar molecular size and physical properties. To address this difficulty, herein, we present an ultramicroporous hydrogen‐bonded organic framework (HOF‐FJU‐1) from tetracyano bicarbazole to separate C2H2 from CO2 by taking advantage of differences in their electrostatic potential distribution. This material possesses a suitable pore environment and electrostatic potential distribution fitting well to C2H2, thus showing extra strong affinity to C2H2 (46.73 kJ mol−1) and the highest IAST selectivity of 6675 for C2H2/CO2 separation among the adsorbents reported. The single crystal X‐ray diffraction reveals that the suitable pore environment in HOF‐FJU‐1 provides multiple C−H⋅⋅⋅π and hydrogen‐bonded interactions N⋅⋅⋅H−C with C2H2 molecules. Dynamic breakthrough experiments demonstrate its outstanding separation performance to C2H2/CO2 mixtures.