For inorganic semiconductors crystalline order leads to a band structure which gives rise to drastic differences to the disordered material. An example is the presence of an indirect band gap. For organic semiconductors such effects are typically not considered, since the bands are normally flat, and the band-gap therefore is direct. Herein we show results from electronic structure calculations demonstrating that ordered arrays of porphyrins reveal a small dispersion of occupied and unoccupied bands leading to the formation of a small indirect band gap. We demonstrate herein that such ordered structures can be fabricated by liquid-phase epitaxy and that the corresponding crystalline organic semiconductors exhibit superior photophysical properties, including large charge-carrier mobility and an unusually large charge-carrier generation efficiency. We have fabricated a prototype organic photovoltaic device based on this novel material exhibiting a remarkable efficiency.

Covalent organic frameworks are a class of crystalline porous polymers that integrate molecular building blocks into periodic structures and are usually synthesized using two-component [1+1] condensation systems comprised of one knot and one linker. Here we report a general strategy based on multiple-component [1+2] and [1+3] condensation systems that enable the use of one knot and two or three linker units for the synthesis of hexagonal and tetragonal multiple-component covalent organic frameworks. Unlike two-component systems, multiple-component covalent organic frameworks feature asymmetric tiling of organic units into anisotropic skeletons and unusually shaped pores. This strategy not only expands the structural complexity of skeletons and pores but also greatly enhances their structural diversity. This synthetic platform is also widely applicable to multiple-component electron donor–acceptor systems, which lead to electronic properties that are not simply linear summations of those of the conventional [1+1] counterparts.

We have extended the Universal Force Field for to cover all moieties present in the most extensive framework library to date, i.e. the Computation-Ready Experimental (CoRE) database (Chem. Mater. 26, 6185 (2014)).Thus, we have extended the parameters to include the fourth and fifth row transition metals, lanthanides and an additional atom type for Sulphur, while the parameters of original UFF and of UFF4MOF are not modified. Employing the new parameters significantly enlarges the number of structures that may be subjected to a UFF calculation, i.e. more than doubling accessible MOFs of the CoRE structures and thus reaching over 99% of CoRE structure coverage. In turn, 95% of optimized cell parameters are within 10% of their experimental values. We contend these parameters will be most useful for the generation and rapid prototyping of hypothetical MOF structures from SBU databases.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are recently notable examples of highly porous polymer frameworks with a raft of potential applications. Synthesis of these compounds is modular, with "connectors" and "linkers" able to be replaced almost at will in the fabrication of isoreticular frameworks (frameworks with the same underlying topology). The range of components available to form such framework structures is vast, leading to a "combinatorial explosion" problem in predicting which framework compounds might have a set of desired properties. Computational investigations can be used in both predictive and explanatory roles in this research but rely on accurate structural models. In this work, we present our software, AuToGraFS, Automated Topological Generator for Framework Structures, and show some of its advanced functionality in "computational reticular chemistry". AuToGraFS is linked to a fully featured force field to produce fully optimized structures of arbitrary frameworks. AuToGraFS, including a graphical user interface, is publicly available for download.