Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

Porous hypercross-linked polymers based on perbenzylated monosugars (SugPOP-1–3) have been synthesized by Friedel–Crafts reaction using formaldehyde dimethyl acetal as an external cross-linker. Three perbenzylated monosugars with similar chemical structure were used as monomers in order to tune the porosity. These obtained polymers exhibit microporous and mesoporous features. The highest Brunauer–Emmett–Teller specific surface area for the resulting polymers was found to be 1220 m2 g−1, and the related carbon dioxide storage capacity was found to be 14.4 wt % at 1.0 bar and 273 K. As the prepared porous polymer SugPOP-1 is based on hemiacetal glucose, Ag nanoparticles (AgNPs) can be successfully incorporated into the polymer by an in situ chemical reduction of freshly prepared Tollens’ reagent. The obtained AgNPs/SugPOP-1 composite demonstrates good catalytic activity in the reduction of 4-nitrophenol (4-NP) with an activity factor k a = 51.4 s−1 g−1, which is higher than some reported AgNP-containing composite materials.

Photolysis (λ 185 nm) of Liquid Tetrahydropyran

The main products of the 185 nm photolysis of neat liquid tetrahydropyran are pent-4-en-l-ol (7) (∅ = 0.40), 2-(5′-hydroxypentyl)tetrahydropyran (10) (0.21), valeraldehyde (6) (0.13), and pentan-1-ol (8) (0.08). These products are thought to be formed via the biradical ·O(CH2)4ĊH2 and/or through intramolecular (6, 7, 8) and intermolecular (10) photoreactions. In the case of 10, the probability of a specific intermolecular photoreaction involving two tetrahydropyran molecules is suggested by the fact that in the photolysis of solutions of tetrahydropyran in cyclohexane and formaldehyde dimethyl acetal products analogous to 10 made up of a tetrahydropyran and a solvent molecule moiety, are not formed.

Photolysis (λ =185 nm) of Liquid Pivalaldehyde Dimethyl Aceta

Deoxygenated liquid pivalaldehyde dimethyl acetal was photolyzed at λ = 185 nm, and 28 products have been determined. The major ones and their quantum yields are: methyl formate (0.47), isobutene (0.39), methane (0.28), neopentane (0.16), isobutane (0.13), formaldehyde dimethyl acetal (0.13), formaldehyde (0.09), methyl neopentyl ether (0.09), methanol (0.07), and methyl pivalate (0.04). The predominant primary photoprocesses are suggested to be the scission of the O–CH3 bond (homolytic, 0.51; molecular, 0.04) and the C-tBu bond (homolytic and molecular, 0.16). Minor processes are the scission of the C–OCH3 (molecular, 0.09; homolytic, 0.03), C–H (0.006), and C–CH3 bonds (< 0.01). The radical (A) eliminates with ease t-butyl (reaction (i)). This process is at least 10 times more efficient than methoxy elimination or hydrogen abstraction from the substrate.[xxx]