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Conductive metal–organic frameworks (MOFs) have recently been applied in electroactive ionic actuators due to their high surface areas and fast ion migration. However, their actuation performance needs to be promoted in terms of high conversion efficiency and large strain. Here, a soft ionic actuator is assembled by designing a hierarchical Cu‐MOFs‐based active material, which is composed of conductive Cu‐catecholate (Cu‐CAT) nanosheets covalently bridged by carboxylic multiwall carbon nanotubes (Cu‐CAT@MWCNT). Benefited from the large electromechanical deformation and rapid response rate of the Cu‐CAT@MWCNT electrodes, the assembled soft actuator exhibits large displacement of 16.6 mm with high bending strain of 0.52% (AC of ±3 V) and a high energy conversion efficiency (3.02%) with cycling stability over 10 000 cycles (in frequency range of 0.1–10 Hz). In addition, it demonstrates the capacity of gripping objects when assembled on a robot. The Cu‐CAT@MWCNT hybrid material‐based electrode points out a feasible pathway to construct soft actuators with improved performance and broadens their applications. [ABSTRACT FROM AUTHOR]

Photoreactive olefinic species are incorporated into a metal–organic framework (MOF), [Zn(bdc)(3‐F‐spy)] (1). Single crystals of 1 are shown to undergo three types of photomechanical macroscopic deformation upon illumination by UV light. To demonstrate the practical potential of this system, the inclusion of 1 in a PVA (polyvinyl alcohol) composite membrane, by exploiting hydrogen‐bonding interactions, is presented. Using this composite membrane, the amplification of mechanical stress to achieve macroscopic actuation behavior is demonstrated. These results pave the way for the generation of MOF‐based soft photoactuators that produce clearly defined mechanical responses upon irradiation with light. Such systems are anticipated to have considerable potential in photomechanical energy harvesting and conversion systems. [ABSTRACT FROM AUTHOR]

The photoinduced dynamic behavior of flexible materials has received considerable attention for potential applications, such as in data storage or as smart optical devices and molecular mechanical actuators. Until now, precisely controlling expansion and contraction with light has remained a challenge. Unraveling the detailed mechanisms of photoinduced structural transformations remains a critical step necessary to understand the molecular architecture necessary for the design of sensitive photomechanical actuators. Herein, a two‐dimensional flexible metal–organic framework [Zn2(bdc)2(3‐CH3‐spy)2]⋅H2O (Zn2‐1; H2bdc=1,4‐benzenedicaboxylic acid; 3‐CH3‐spy=3‐methylstyrylpyridine) with a positive volumetric thermal expansion coefficient of +78.78×10−6 K−1 is reported. Upon light irradiation at different wavelengths, the MOF underwent a [2+2] cycloaddition, which afforded a family of isomeric, three‐dimensional MOFs (Zn2‐2 n, n=a–d) in a single‐crystal‐to‐single‐crystal (SCSC) manner. An unprecedented phenomenon, that is, photoinduced nonlinear contraction (PINC), was observed during this conversion. The PINC is caused by conformational changes in the 3‐CH3‐spy and bdc2− ligands, the bending of metal–ligand bonds, and the local distortion of the paddle‐wheel SBUs. The formation of a "wrinkle morphology" on the crystal surface after the photoreaction was observed by AFM. This PINC behavior can broaden the studies on materials expansion and offer a photodriven approach for the future design of supersensitive photomechanical actuators. [ABSTRACT FROM AUTHOR]

We herein report a fluorescent Zn(ii)-supported metal–organic framework (MOF) [Zn4(Hbpvp)2(BTC)3(HCOO)(H2O)2]·4H2O (1) (bpvp = 3,5-bis-(2-(pyridin-4-yl)vinyl)pyridine; H3BTC = 1,3,5-benzenetricarboxylic acid) assembled from solvothermal reactions of ZnSO4·7H2O with bpvp and H3BTC ligands. Compound 1 has a unique two-dimensional (2D) layer structure and exhibits a high sensitivity and a low limit of detection of 1.0 × 10−6 mol L−1 for both 2,4-dinitrophenol (2,4-DNP) and p-benzoquinone (p-BQ) in aqueous solutions, inferred from fluorescence quenching studies. The fluorescent intensity of 1 recovers upon removal of analytes, making it a promising recyclable dual-targeted luminescent probe for 2,4-DNP and p-BQ in water. [ABSTRACT FROM AUTHOR]