Surface modification of zeolites using benzene-1,4-diboronic acid to form gated micropores with mild and photo responsive pore reopening

Regularly arranged pore structures are effective for regulating molecular permeation processes. Microporous zeolite materials are advantageous to manipulate the diffusion of gaseous molecules. Especially, zeolitic membranes are actively utilized in a number of membrane separation processes. Recently, we have reported that some disilylbenzene compounds grafted onto the surfaces of mordenite and ZSM-5 zeolites sealed their micropores to restrict the penetrations of molecular nitrogen, and that the calcination and heated HCl treatment reopened the sealed micropores. This paper reports that the micropores of mordenite and ZSM-5 zeolites were also sealed with the surface modification using benzene-1,4-diboronic acid, and molecular nitrogen cannot permeate into the micropores thus closed. This modification process provided some milder reopening of the sealed micropores such as diluted HCl treatment at room temperature. The reopening process was also successful by the UV irradiation to the solid zeolite samples after the impregnation of photo-acid generator (PAG). The pore reopening of the micropores with photo-irradiation in solid phase is a unique technique that will be applicable for some manipulation technologies of gaseous molecules.