title: Near-IR squaraine dye-loaded gated periodic mesoporous organosilica for photo-oxidation of phenol in a continuous-flow device.
abstract: Periodic mesoporous organosilica (PMO) has been widely used for the fabrication of a variety of catalytically active materials. We report the preparation of novel photo-responsive PMO with azobenzene-gated pores. Upon activation, the azobenzene gate undergoes trans-cis isomerization, which allows an unsymmetrical near-infrared squaraine dye (Sq) to enter into the pores. The gate closure by cis-trans isomerization of the azobenzene unit leads to the safe loading of the monomeric dye inside the pores. The dye-loaded and azobenzene-gated PMO (Sq-azo@PMO) exhibits excellent generation of reactive oxygen species upon excitation at 664 nm, which can be effectively used for the oxidation of phenol into benzoquinone in aqueous solution. Furthermore, Sq-azo@PMO as the catalyst was placed inside a custom-built, continuous-flow device to carry out the photo-oxidation of phenol to benzoquinone in the presence of 664-nm light. By using the device, about 23% production of benzoquinone with 100% selectivity was achieved. The current research presents a prototype of transforming heterogeneous catalysts toward practical use.
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore.
authors.forename: Parijat
authors.initials: P
authors.lastname: Borah
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore.
authors.forename: Sivaramapanicker
authors.initials: S
authors.lastname: Sreejith
authors.affiliation: Photosciences and Photonics Group, Chemical Sciences and Technology Division, Council of Scientific and Industrial Research-National Institute for Interdisciplinary Science and Technology, Trivandrum 695019, India.
authors.forename: Palapuravan
authors.initials: P
authors.lastname: Anees
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459 Singapore, Singapore.
authors.forename: Nishanth Venugopal
authors.initials: NV
authors.lastname: Menon
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459 Singapore, Singapore.
authors.forename: Yuejun
authors.initials: Y
authors.lastname: Kang
authors.affiliation: Photosciences and Photonics Group, Chemical Sciences and Technology Division, Council of Scientific and Industrial Research-National Institute for Interdisciplinary Science and Technology, Trivandrum 695019, India.
authors.forename: Ayyappanpillai
authors.initials: A
authors.lastname: Ajayaghosh
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore. ; School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore, Singapore.
authors.forename: Yanli
authors.initials: Y
authors.lastname: Zhao
keywords: microfluidic device; periodic mesoporous organosilica; photo-oxidation; singlet oxygen; squaraine dye