Metal defects in HKUST-1 MOF revealed by vibrational spectroscopy: a combined quantum mechanical and experimental study

Abstract

This paper reports an interpretation of the FTIR and Raman spectra of the HKUST-1 MOF in light of an ab initio theoretical analysis of the vibrational spectra of the framework. Several models, with different degrees of complexity have been compared in terms of their capability of reproducing structural parameters and vibrational behavior. Satisfactory simulations have been obtained only by considering a complete periodic model accounting for the totality of the structural features. Simpler models limited to a single paddlewheel motif are found to be too inaccurate for an effective vibrational analysis. A number of signals have been identified that are characteristic of framework defects. These were properly simulated by introducing specific functional groups in the framework, thus confirming the chemical nature of the defects and identifying spectroscopic signatures for their recognition. The complete vibrational analysis reported herein revises a number of literature assignments relevant for the study of host/guest molecular interactions.