Microporous Hydrogen-Bonded Organic Framework for Highly Efficient Turn-Up Fluorescent Sensing of Aniline

A microporous three-dimensional (3D)
hydrogen-bonded organic framework
(HOF-20) has been constructed from an aromatic-rich tetratopic carboxylic
acid, 5-(2,6-bis­(4-carboxyphenyl)­pyridin-4-yl)­isophthalic acid (H4BCPIA). The activated HOF-20a has a moderately high Brunauer–Emmett–Teller
(BET) surface area of 1323 m2 g–1 and
excellent stability in water and HCl aqueous solution. HOF-20 exhibits
highly efficient turn-up fluorescent sensing of aniline in water with
a detection limit of 2.24 μM and is selective toward aniline
in the presence of aromatic interferents, owing to the hydrogen bonding
and edge-to-face π–π stacking interactions between
the HOF-20 host and the guest aniline molecules, as demonstrated in
the single-crystal X-ray structure of HOF-20⊃aniline. Density
functional theory (DFT) calculations further demonstrate that the
recognition of aniline molecules by HOF-20 could restrict the rotation
of the aromatic rings in H4BCPIA linkers, reducing the
nonradiative decay pathways upon photoexcitation and subsequently
enhancing the fluorescence intensity.