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In photo‐induced charge separation, organic thin films with donor and acceptor chromophores are vital for uses such as artificial photosynthesis and photodetection. The main challenges include optimizing charge separation efficiency and identifying the ideal acceptor/donor ratio. Achieving this is difficult due to the variability in molecular configurations within these typically amorphous organic aggregates. Metal–organic frameworks (MOFs) provide a structured solution by enabling systematic design of donor/acceptor blends with adjustable ratios within a crystalline lattice. We demonstrate this approach by incorporating donor and acceptor naphthalenediimide (NDI) chromophores as linkers in a highly oriented, monolithic MOF thin film. By adjusting the NDI acceptor linker concentration during the layer‐by‐layer assembly of surface‐anchored MOF thin films (SURMOFs), we significantly enhanced charge separation efficiency. Surprisingly, the optimum acceptor concentration was only 3 %, achieving a forty‐fold increase in photodetection efficiency compared to baseline NDI donor‐based SURMOFs. This unexpected behaviour was clarified through theoretical analysis enabled by the well‐defined crystalline structure of the SURMOFs. Using density functional theory and kinetic Monte Carlo simulations, we identified two opposing effects from acceptors: the positive effect of suppressing undesirable charge carrier recombination is offset at high concentrations by a reduction in charge‐carrier mobility. [ABSTRACT FROM AUTHOR]

Organic semiconductors, specifically polycyclic aromatic chromophores like pentacene, coronene, and nanographenes (hexa‐peri‐hexabenzocoronene, HBC), are often utilized in optoelectronic applications due to their intriguing single‐molecule properties. However, the integration of these aromatic compounds into optoelectronic devices frequently encounters significant obstacles, primarily due to the unpredictable and challenging control over the structure and morphology of their condensed phase. Rather than resorting to chemical modifications or advanced thin‐film manufacturing methods such as chemical vapor deposition, the so‐called metal‐organic framework (MOF) approach is employed to create a highly photoresponsive, nanographene‐based thin film employing a layer‐by‐layer, liquid‐phase epitaxy method. It is demonstrated that the novel Cu‐HBC MOF thin film exhibits excellent photoresponsive behavior under ultraviolet illumination, including a fast response time (˂ 0.02 s) and high current switching ratio (≈104), which significantly outperforms an isostructural MOF Zn‐HBC. Furthermore, it is demonstrated that the metal nodes inside the MOF can be used to enhance the photoresponse by efficient exciton splitting. [ABSTRACT FROM AUTHOR]

Transport diffusivity of molecules in a porous solid is constricted by the rate at which molecules move from one pore to the other, along the concentration gradient, i.e. by following Fickian diffusion. In heterogeneous porous materials, i.e. in the presence of pores of different sizes and chemical environments, diffusion rate and directionality remain tricky to estimate and adjust. In such a porous system, we have realized that molecular diffusion direction can be orthogonal to the concentration gradient. To experimentally determine this complex diffusion rate dependency and get insight of the microscopic diffusion pathway, we have designed a model nanoporous structure, metal-organic framework (MOF). In this model two chemically and geometrically distinct pore windows are spatially oriented by an epitaxial, layer-by-layer growth method. The specific design of the nanoporous channels and quantitative mass uptake rate measurements have indicated that the mass uptake is governed by the interpore diffusion along the direction orthogonal to the concentration gradient. This revelation allows chemically carving the nanopores, and accelerating the interpore diffusion and kinetic diffusion selectivity. In heterogeneous porous systems diffusion rate is controlled by pore window sizes and concentration gradient. Here authors show that in a porous metal-organic framework system, the diffusion direction can be orthogonal to the concentration gradient. [ABSTRACT FROM AUTHOR]

Differently functionalized porphyrin linkers represent the key compounds for the syntheses of new porphyrin‐based metal–organic frameworks (MOFs), which have gathered great interest within the last two decades. Herein we report the synthesis of a large range of 5,15‐bis(4‐ethoxycarbonylphenyl)porphyrin derivatives, through Suzuki and Sonogashira cross‐coupling reactions of an easily accessible corresponding meso‐dibrominated trans‐A2B2‐porphyrin with commercially available boronic acids or terminal alkynes. The resulting porphyrins were fully characterized through NMR, MS, and IR spectroscopy and systematically investigated through UV/Vis absorption. Finally, selected structures were saponified to the corresponding carboxylic acids and subsequently proven to be suitable for the synthesis of surface‐anchored MOF thin films. [ABSTRACT FROM AUTHOR]

Several photophysical properties of chromophores depend crucially on intermolecular interactions. Thermally‐activated delayed fluorescence (TADF) is often influenced by close packing of the chromophore assembly. In this context, the metal‐organic framework (MOF) approach has several advantages: it can be used to steer aggregation such that the orientation within aggregated structures can be predicted using rational approaches. We demonstrate this design concept for a DPA‐TPE (diphenylamine‐tetraphenylethylene) chromophore, which is non‐emissive in its solvated state due to vibrational quenching. Turning this DPA‐TPE into a ditopic linker makes it possible to grow oriented MOF thin films exhibiting pronounced green electroluminescence with low onset voltages. Measurements at different temperatures clearly demonstrate the presence of TADF. Finally, this work reports that the layer‐by‐layer process used for MOF thin film deposition allows the integration of the TADF‐DPA‐TPE in a functioning LED device. [ABSTRACT FROM AUTHOR]

Graphical abstract The oxidative polymerization of terthiophene and a substituted thiophene has been successfully carried out inside the pores of surface anchored metal-organic frameworks (SURMOFs). Using SURMOF-2 thin film as a porous host, terthiophene and 3,4-ethylenedioxythiophene monomers are oligomerized into oligomers. The ease of deposition of these oligomer:MOF composite thin films on transparent, conductive substrates offers possibilities for future optolelectronic applications. Highlights • Terthiophene and 3,4-Ethylenedioxythiophene have been encapsulated inside the 1D pores of SURMOF thin films and oligomerized by chemical oxidation method. • Inside the nanochannels of SURMOFs only short chain oligomers are formed. • PEDOT:MOF thin film was found to be electrically conductive. • Control of oligomer chain length and fabrication of oligomer:MOF composite on transparent and conductive substrates as thin film, both are of great significance towards future optoelectronic applications of polymer/oligomer:MOF composite. Abstract Films consisting of surface-anchored metal-organic frameworks (SURMOFs) which are prepared by layer-by-layer deposition techniques can be used as highly oriented crystalline template structures for oligomerization processes. Herein, SURMOF films of Zn(bdc) (1) and, Cu(bpdc) (2) were prepared, which consist of lamellar ordered 2D MOF sheets forming 1D channels as the host structures for oligomerization of terthiophene (Tth) and, 3,4-ethylenedioxythiophene (EDOT), respectively. After SURMOF preparation, the pores were filled either with Tth or EDOT and the oligomerization was initiated by oxidizing agents, such as I 2 and FeCl 3. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF/MS), the short chains of polyterthiophene (PTth) and poly(3,4-ethylenedioxythiophene) (PEDOT) were characterized. FT-IR and Raman spectroscopy further confirmed the presence of oligomers inside the pores of the SURMOFs. Using the SURMOF thin films as template, a homogeneously distributed conductive MOF-PEDOT composite coating can be achieved, with potential applications in optoelectronics. [ABSTRACT FROM AUTHOR]

By using a layer‐by‐layer (LbL) approach, lanthanide‐based, monolithic metal–organic framework (MOF) thin films are fabricated for optical applications. In particular, the LbL approach allows manufacturing of heteroepitaxial Tb(III)‐Eu(III)(BTC) coatings with precise thickness control. Adjusting the Tb(III)‐to‐Eu(III) ratio allows tuning of the emission color. The hetero‐multilayer architecture makes it possible to suppress the direct Tb(III)‐to‐Eu(III) energy transfer, an unwanted phenomenon present in the corresponding mixed‐metal bulk MOF structures. The resulting Ln‐MOF thin films, or Ln‐surface‐anchored MOFs (SURMOFs), are characterized by X‐ray diffraction, infra‐red reflection absorption spectroscopy, UV–vis, and photoluminescence measurements. The results demonstrate that the heteroepitaxial SURMOF architectures carry huge potential for fabricating optical coatings for a wide range of applications. [ABSTRACT FROM AUTHOR]