Quantum chemistry investigation of rigid A-IRMOF-M0 series (A = zinc, cadmium, and alkaline-earth metals) on crystal structure, electronic structure, formation energy, chemical bonding, and optical properties

A class of rigid isoreticular metal-organic frameworks (A-IRMOF-M0, A = Zn, Cd, alkaline-earth metals) were systematically investigated using DFT calculations. The calculated lattice parameters supplement the incomplete available theoretical structural parameters for Zn-IRMOF-M0, and extends the prediction to the remaining members of this series. The estimated bulk moduli of A-IRMOF-M0 series range from 16.4 to 45.3 GPa indicating relatively soft materials, but still rank the most rigid ones in the IRMOF series. The electronic structure calculations demonstrated that the band gap for A-IRMOF-M0 series is ca. 3.2-3.7 eV, indicating all are semiconductors. The large magnitude of estimated formation energies (-53 to -88 kJ/mol), indicative of very high stabilities of IRMOF-M0 series. The linear optical properties of these materials were systematically investigated, which demonstrated that A-IRMOF-M0 series have much stronger optical responses than that of MOF-5 (e.g., using the lower photon energy can obtain responses as strong as that of MOF-5). This provides very useful and detailed information for the experimental confirmation and the potential application of A-IRMOF-M0 series as solar cell materials and opto-electronic devices. The detailed analysis of chemical bonding in the A-IRMOF-M0 series reveals the nature of the A-O, O-C, and C-C bonds, i.e., the A-O bond has mainly ionic interaction whereas O-C and C-C exhibit mainly covalent interactions. The findings in this paper might contribute to a comprehensive understanding about this kind of material and shed insight into the synthesis and application of novel and robust MOFs. (C) 2013 Elsevier Inc. All rights reserved.