Electronic chemical potentials of porous metal-organic frameworks

The binding energy of an electron in a material is a fundamental characteristic, which determines a wealth of important chemical and physical properties. For metal-organic frameworks this quantity is hitherto unknown. We present a general approach for determining the vacuum level of porous metal-organic frameworks and apply it to obtain the first ionisation energy for six prototype materials including zeolitic, covalent and ionic frameworks. This approach for valence band alignment can explain observations relating to the electrochemical, optical and electrical properties of porous frameworks

Chemical principles underpinning the performance of the metal–organic framework HKUST-1

A common feature of multi-functional metal–organic frameworks is a metal dimer in the form of a paddlewheel, as found in the structure of Cu3(btc)2 (HKUST-1). The HKUST-1 framework demonstrates exceptional gas storage, sensing and separation, catalytic activity and, in recent studies, unprecedented ionic and electrical conductivity. These results are a promising step towards the real-world application of metal–organic materials. In this perspective, we discuss progress in the understanding of the electronic, magnetic and physical properties of HKUST-1, representative of the larger family of Cu⋯Cu containing metal–organic frameworks. We highlight the chemical interactions that give rise to its favourable properties, and which make this material well suited to a range of technological applications. From this analysis, we postulate key design principles for tailoring novel high-performance hybrid frameworks

Ligand design for long-range magnetic order in metal-organic frameworks

We report a class of ligands that are candidates to construct metal-organic frameworks with long-range magnetic order between transition metal centres. Direct quantum chemical calculations predict Neel temperatures exceeding 100 K for the case of Mn

Ligand design for long-range magnetic order in metal-organic frameworks

We report a class of ligands that are candidates to construct metal–organic frameworks with long-range magnetic order between transition metal centres. Direct quantum chemical calculations predict Néel temperatures exceeding 100 K for the case of Mn

Electronic structure design for nanoporous, electrically conductive zeolitic imidazolate frameworks

Electronic structure calculations are used to develop design rules for enhanced electrical conductivity in zeolitic imidazolate frameworks. The electrical resistivity of Co2+ based zeolitic imidazolate frameworks has previously been found to be ∼1000 times lower than that of Zn2+ based materials. The electrical conductivity of the frameworks can also be tuned by ligand molecule selection. Using density functional theory calculations, this controllable electrical conductivity is explained in terms of tuneable conduction band edge character, with calculations revealing the improved hybridisation and extended band character of the Co2+ frameworks. The improvements in the methylimidazolate frameworks are understood in terms of improved frontier orbital matching between metal and ligand. The modular tuneability and previously demonstrated facile synthesis provides a route to rational design of stable framework materials for electronic applications. By outlining these design principles we provide a route to the future development of stable, electrically conductive zeolitic imidazolate frameworks

Cyclopropenium (C3H3)+(C_3H_3)^+ as an Aromatic Alternative A-Site Cation for Hybrid Halide Perovskite Architectures

Hybrid halide perovskites are an emerging class of photovoltaic materials, boasting high solar efficiencies from relatively simple preparations. However, the chemical diversity of the A-site organic cation is limited, generally due to steric constraints of the (PbI3)− cage. Herein we describe the use of a non-benzenoid Hückel aromatic, $(C_3H_3)^+$, as a viable alternative to the readily employed methylammonium, formamidinium, and guanidinium A-site cations. $(C_3H_3)^+$ may lead to greater moisture stability due to the lack of an acidic proton relative to the current $(H-NR_3)+$-based systems while still boasting a narrow electronic band gap $(E_g=1.5eV)$ and mobile holes and electrons $(m_h*=-1.27$ and $m_e*=0.77$, respectively)

Computational screening of structural and compositional factors for electrically conductive coordination polymers

The combination of organic and inorganic chemical building blocks to form metal–organic frameworks (MOFs) offers opportunities for producing functional materials suitable for energy generation, storage and conversion. However, such applications rely on robust electron transport and the design of conductive hybrid materials is still in its infancy. Here we apply density functional theory to assess the important structural and compositional factors for forming conducting MOFs. We focus on 1D metal–organic polymers as a model system and assess the choice of organic, inorganic and linking units. The results demonstrate that electronic communication is sensitive to the energy and symmetry of the frontier orbitals associated with the organic and inorganic building blocks and offers guidance on how to optimise electrical conduction in hybrid materials

Computational screening of structural and compositional factors for electrically conductive coordination polymers

The combination of organic and inorganic chemical building blocks to form metal-organic frameworks (MOFs) offers opportunities for producing functional materials suitable for energy generation, storage and conversion. However, such applications rely on robust electron transport and the design of conductive hybrid materials is still in its infancy. Here we apply density functional theory to assess the important structural and compositional factors for forming conducting MOFs. We focus on 1D metal-organic polymers as a model system and assess the choice of organic, inorganic and linking units. The results demonstrate that electronic communication is sensitive to the energy and symmetry of the frontier orbitals associated with the organic and inorganic building blocks and offers guidance on how to optimise electrical conduction in hybrid materials