Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) consist of molecular building blocks being stitched together by strong bonds. They are well known for their porosity, large surface area, and related properties. The electronic properties of most MOFs and COFs are the superposition of those of their constituting building blocks. If crystalline, however, solid-state phenomena can be observed, such as electrical conductivity, substantial dispersion of electronic bands, broadened absorption bands, formation of excimer states, mobile charge carriers, and indirect band gaps. These effects emerge often by the proximity effect caused by van der Waals interactions between stacked aromatic building blocks. Herein, it is shown how functionality is imposed by this proximity effect, that is, by stacking aromatic molecules in such a way that extraordinary properties emerge in MOFs and COFs. After discussing the proximity effect in graphene-related materials, its importance for layered COFs and MOFs is shown. For MOFs with well-defined structure, the stacks of aromatic building blocks can be controlled via varying MOF topology, lattice constant, and by attaching steric control units. Finally, an overview of theoretical methods to predict and analyze these effects is given, before the layer-by-layer growth technique for well-ordered surface-mounted MOFs is summarized.

In organic photovoltaics, porphyrins (PPs)a re among the most promising compounds owing to their large absorption cross-section,w ide spectralr ange, and stability. Nevertheless, ap recise adjustment of absorption band positionst or each af ull coverage of the so-called green gap has not been achieved yet. We demonstrate that at uning of the PP Q-and Soret bands can be carried out by using ac omputationala pproach for which substitution patterns are optimized in silico. Themostpromising candidate structures were then synthesized. The experi-mentalU V/Vis data for the solvated compounds were in excellent agreement with the theoretical predictions. By attaching further functionalities, which allow the use of PP chromophores as linkers for the assembly of metal-organic frameworks (MOFs), we werea ble to exploit packinge ffects resulting in pronounced redshifts, whichallowed further optimization of the photophysical properties of PP assemblies. Finally,w eu se al ayer-by-layer methodt oa ssemble the PP linkers into surface-mountedM OFs (SUR-MOFs),t huso btainingh igh optical quality,h omogeneous and crystalline multilayer films. Experimental results are in full accordw ith the calculations, demonstrating the huge potential of computational screening methodsi nt ailoring MOF and SURMOF photophysical properties.While presently the highest conversion efficiencies are achieved with inorganic (Si, Ge) [1] and hybrid (Grätzel-cell, perovskites) [2] semiconductor-based photovoltaic (PV) devices, or- [a] Dr.

Time‐dependent density functional theory is thoroughly benchmarked for the predictive calculation of UV–vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large‐scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q‐bands, the results given by various computational protocols, including basis sets, density‐functionals (including gradient corrected local functionals, hybrids, double hybrids and range‐separated functionals), and various variants of time‐dependent density functional theory, including the simplified Tamm–Dancoff approximation, are compared. An excellent choice for these calculations is the range‐separated functional CAM‐B3LYP in combination with the simplified Tamm–Dancoff approximation and a basis set of double‐ζ quality def2‐SVP (mean absolute error [MAE] of ≈0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ≈0.04 eV).

<div>Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) consist of molecular building blocks being stitched together by strong bonds. They are well known for their porosity, large surface area, and related properties. The electronic properties of most MOFs and COFs are the superposition of those of their constituting building blocks. If crystalline, however, solid-state phenomena can be observed, such as electrical conductivity, substantial dispersion of electronic bands, broadened absorption bands, formation of excimer states, mobile charge carriers, and indirect band gaps. These effects emerge often by the proximity effect caused by the van-der-Waals interactions between stacked aromatic building blocks. This Progress Report shows how functionality is imposed by this proximity effect, that is, by stacking aromatic molecules in such a way that extraordinary electronic and optoelectronic properties emerge in MOFs and COFs. After discussing the proximity effect in graphene-related materials, its importance for layered COFs and MOFs is shown. For MOFs with well-defined structure, the stacks of aromatic building blocks can be controlled via varying MOF topology, lattice constant, and by attaching steric control units. Finally, an overview of theoretical methods to predict and analyze these effects is given, before the layer-by-layer growth technique for well-ordered surface-mounted MOFs is summarized.</div>

Chemically-derived graphene have been synthesized by modified Hummers method and reduced using sodium borohydride. To explore the potential for photovoltaic applications, graphene/p-silicon (Si) heterojunction devices were fabricated using a simple and cost effective technique called spin coating. The SEM analysis shows the formation of graphene oxide (GO) flakes which become smooth after reduction. The absence of oxygen containing functional groups, as observed in FT-IR spectra, reveals the reduction of GO, i.e., reduced graphene oxide (rGO). It was further confirmed by Raman analysis, which shows slight reduction in G-band intensity with respect to D-band. Hall effect measurement confirmed n-type nature of rGO. Therefore, an effort has been made to simu- late rGO/p-Si heterojunction device by using the one-dimensional solar cell capacitance software, considering the experimentally derived parameters. The detail analysis of the effects of Si thickness, graphene thickness and temperature on the performance of the device has been presented.