Fluorescent and Catalytic Properties of a 2D Lamellar Zn Metal–Organic Framework with sql Network Structure

A two-dimensional (2D) lamellar Zn metal–organic framework (Zn-MOF, <b>1</b>) with a fluorescent 1,6-di(pyridin-3-yl)pyrene (3-DPPy) and 1,4-benzenedicarboxylate (BDC²⁻) bridging linkers was prepared and structurally characterized. The chemical formula of <b>1</b> is [Zn(μ-3-DPPy)(μ-BDC)]_n. The mononuclear Zn(II) ion, acting as a node, is tetrahedrally coordinated with two 3-DPPy and two BDC linkers. The coordination environment of Zn(II) is a distorted tetrahedral geometry. The Zn-MOF is the <b>sql</b> network structure based on topology analysis. The undulated 2D sheets of <b>1</b> tightly pack together to form a lamellar structure. The pyrene moieties are parallelly oriented to each other. The Zn-MOF is not porous, possibly because the mononuclear Zn(II) node did not form cluster-based secondary building units due to the less symmetric 3-DPPy. The steady-state fluorescence measurements indicate that the fluorescence signal of the <b>1</b> is slightly blue-shifted compared to the free 3-DPPy in the solid state. The excimer emission band at 463 nm for crystalline 3-DPPy is shifted to 447 nm for <b>1</b>. The value of 447 nm is also a blue-shift value compared to nonsubstituted pyrene crystals (470 nm). Despite its nonporosity, the surface Lewis acidic sites of <b>1</b> could catalyze the transesterification of esters. Surface defect sites are responsible for this catalytic activity.