Diffuse reflectance Fourier transform infrared (DRIFT-IR) spectroscopy was employed to characterize a range of zeolites and zeolite-like molecular sieves in their powdered forms. Whiles spectra were collected from 8500 cm-1 to 150 cm-1, the far-IR region (400 cm-1 - 10 cm-1, but typically < 650 cm-1 in practice) was of particular interest as it can yield information on bonding of heavier elements, such as metals within the framework of the zeolite, tetrahedral atom-oxygen bending, and pore openings in zeolites. The advantage of these particular experiments is that diffuse reflection spectroscopy permits IR spectra of powders to be acquired with a minimum of sample preparation. Far-IR spectra result from vibrations involving elements heavier than those typically observed in mid-IR spectra or coordinated vibrations involving structures such as rings. Such species are expected with the zeolite-like materials being considered and in the products resulting from processes such as ion-exchange or calcination. Thus, these experiments are expected to address the questions often asked of these materials more directly than other spectroscopic techniques.
Results are presented for a series of zincosilicates with different framework structures (VPI-7, VPI-9, and VPI-10). Dramatic differences were observed across the far-IR region for each of the materials. Spectra are compared for as-made samples as well as calcined, ion-exchanged, and intentionally collapsed samples. Subtle differences in the far-IR region were identified for materials that had the same crystalline framework but different composition (zeolite beta (*BEA) and the zincosilicate CIT-6, treated to yield pure silicate, aluminosilicate, and zincosilicate forms).