Isolation and evolution of labile sulfur allotropesviakinetic encapsulation in interactive porous networks

Abstract

The isolation and characterization of small sulfur allotropes have long remained unachievable because of their extreme lability. This study reports the first direct observation of disulfur (S2) with X-ray crystallography. Sulfur gas was kinetically trapped and frozen into the pores of two Cu-based porous coordination networks containing interactive iodide sites. Stabilization of S2was achieved either through physisorption or chemisorption on iodide anions. One of the networks displayed shape selectivity for linear molecules only, therefore S2was trapped and remained stable within the material at room temperature and higher. In the second network, however, the S2molecules reacted further to produce bent-S3species as the temperature was increased. Following the thermal evolution of the S2species in this network using X-ray diffraction and Raman spectroscopy unveiled the generation of a new reaction intermediate never observed before, thecyclo-trisulfur dication (cyclo-S32+). It is envisaged that kinetic guest trapping in interactive crystalline porous networks will be a promising method to investigate transient chemical species.