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Efficient photon-harvesting materials require easy-to-deposit materials exhibiting good absorption and excited-state transport properties. We demonstrate an organic thin-film material system, a palladium–porphyrin-based surface-anchored metal–organic framework (SURMOF) thin film that meets these requirements. Systematic investigations using transient absorption spectroscopy confirm that triplets are very mobile within single crystalline domains; a detailed analysis reveals a triplet transfer rate on the order of 1010s–1. The crystalline nature of the SURMOFs also allows a thorough theoretical analysis using the density functional theory. The theoretical results reveal that the intermolecular exciton transfer can be described by a Dexter electron exchange mechanism that is considerably enhanced by virtual charge-transfer exciton intermediates. On the basis of the photophysical results, we predict exciton diffusion lengths on the order of several micrometers in perfectly ordered, single-crystalline SURMOFs. In the presently available samples, strong interactions of excitons with domain boundaries present in these metal–organic thin films limit the diffusion length to the diameter of these two-dimensional grains, which amount to about 100 nm. Our results demonstrate high potential of SURMOFs for light-harvesting applications.

A solvent responsive, dynamic, three-dimensional supramolecular porous host has been synthesized and structurally characterized. The structural flexibility is realized by the guest responsive structural transformation and also by the different gas and solvent vapor adsorption studies. Noncovalent encapsulation of fluorescein dye into the framework resulted in dual emission through host-to-guest partial energy transfer which is utilized for solvent sensing. Diffusion of solvents modulates the structural arrangement and energy transfer.

A highly luminescent tetrameric zinc(II) complex, {[Zn4(adc)3(bpz)6(HCOO)2]·2H2O} (1; adc = 9,10-anthracenedicarboxylate and bpz = bipyridophenazine), was synthesized by a solvothermal technique and characterized by single-crystal X-ray diffraction. The linear tetrameric units extend into three dimensions via π stacking of adc/bpz and bpz/bpz and multiple CH−π interactions. The compound shows strong red emission at 597 nm (λex= 480 nm), which is attributed to charge-transfer (CT) emission within an adc/bpz donor–acceptor pair. This is also supported by density functional theory computations. Interestingly, the CT emission is amplified by energy transfer from another adc linker that is not involved in the CT interaction.

Here we report the synthesis and structural characterizations of a new 3D functional metal–organic framework {[K8(PTC)2(H2O)1.5]·4H2O}nformed by the self-assembly of KIand chromophoric linker perylenetetracarboxylate (PTC). The structure determination shows a 3D pillared-layer framework, where perylene cores are arranged in an unusual end-to-end off-slipped and zigzag arrangement directed by KI–carboxylate bonding. Photophysical studies revealed a broad absorption band with λmaxof 531 nm and bathochromically shifted red emission centered at 655 nm. This characteristic emission has been assigned due to J-coupling of the PTC linkers in the solid state. The framework contains 1D water-filled channel, and the desolvated framework shows permanent porosity, “as realized by type-I CO2adsorption profile at 195 K. Interestingly, the guest and coordinated water molecules in the framework are connected via H-bonding and based on these characteristics, the framework was further exploited for proton conduction. It shows remarkable conductivity of 1 × 10–3S cm–1under ambient conditions (98% RH) with low activation energy.

Easy-to-integrate, remote read-out thermometers with fast response are of huge interest in numerous application fields. In the context of optical read-out devices, sensors based on the emission of lanthanides (Eu(III), Tb(III)) are particularly promising. Here, by using a layer-by-layer (LbL) approach in the liquid-phase epitaxy process, a series of continuous, low-thickness lanthanide-MIL-103 SURMOFs were fabricated to yield highly sensitive thermometers with optical readout. These Ln-SURMOFs exhibit remarkable temperature-sensing photoluminescence behavior, which can be read out using the naked eye. High transmittance is realized as well by precisely controlling the film thickness and the quality of these Ln-SURMOF thermometers. Moreover, we demonstrate that the thermal sensitivity can be improved in the temperature regime above 120 K, by controlling the energy transfer between Tb(III) and Eu(III). This performance is achieved by employing a sophisticated supramolecular architecture, namely MOF-on-MOF heteroepitaxy.

Exciting assemblies: A metal–organic self‐assembly of pyrenebutyric acid (PBA), 1,10‐phenanthroline (o‐phen), and MgIIshows solid‐state fluorescence originating from a 1:1 PBA–o‐phen exciplex. This exciplex fluorescence is sensitized by another residual PBA chromophore through an excited‐state energy‐transfer process. The solvent polarity modulates the self‐assembly and the corresponding exciplex as well as the energy transfer, resulting in tunable emission of the hybrid (see figure).

Metal–organic frameworks (MOFs) built from different building units offer functionalities going far beyond gas storage and separation. In connection with advanced applications, e.g., in optoelectronics, hierarchical MOF-on-MOF structures fabricated using sophisticated methodologies have recently become particularly attractive. Here, we demonstrate that the structural complexity of MOF-based architectures can be further increased by employing highly spatioselective photochemistry. Using a layer-by-layer, quasi-epitaxial synthesis method, we realized a photoactive MOF-on-MOF hetero-bilayer consisting of a porphyrinic bottom layer and a tetraphenylethylene (TPE)-based top layer. Illumination of the monolithic thin film with visible light in the presence of oxygen gas results in the generation of reactive oxygen species (1O2) in the porphyrinic bottom layer, which lead to a photocleavage of the TPE units at the internal interface. We demonstrate that this spatioselective photochemistry can be utilized to delaminate the top layers, yielding two-dimensional (2D) MOF sheets with well-defined thickness. Experiments using atomic force microscopy (AFM) demonstrate that these platelets can be transferred onto other substrates, thus opening up the possibility of fabricating planar MOF structures using photolithography.