Color-Tuning and Near-Sunlight White Emission in Highly Stable Rod-Spacer MOFs with Defective Dicubane Based Lead(II)-Carboxyl Chains

Abstract

The active lone pair electron effect and highly flexible coordination geometry of Pb 2+ prevented the rational construction of metal−organic frameworks (MOFs) but promoted excellent fluorescence tuning. The regulation on organic and alkali templates facilitated the assemblies of three new Pb-MOFs: [Pb 2 (pia) 2 (DMA)]•DMA (1), [Pb 2 (pia) 2 (DMF)]•1.5DMF (2), and [Pb 2 (pia) 2 (DMF)]•NEt 3 (3). They were rigid rod-spacer and double-walls frameworks, which possess defective dicubane [Pb 4 O 6 ] based metal-carboxyl chains constructed from both semidirected and holodirected Pb 2+ ions. These MOFs exhibited thermal stability up to 370 °C and unprecedented chemical stability in H 2 O and acidic (pH 2) and alkaline (pH 12) aqueous solutions, found for the first time in Pb-MOFs. A single-phase and rareearth-free white-emitting phosphor, 1, was screen out, which showed a near-sunlight and human-vision-friendly broadband spectrum covering the full visible region, possessing the close-to-pure-white chromaticity coordinates of (0.332, 0.347), a near-daylight color temperature of 5696 K, and a high color rendering index of 95. The replacement of DMF as apical ligand and guest in 2 resulted in an intrinsic single and narrow emission at 562 nm with yellow color. The convenient yellow-and-blue color-tuning until white for 2 was realized by either solution or solid blending with blue-emissive H 2 pia, benefited from their highly matched excitation spectra. Using large NEt 3 as template guest induced great framework distortion for 3 and led to white emission with chromaticity coordinates of (0.302, 0.294), stemming from nonequivalent dual emission at 450 and 545 nm. In-depth structure analysis revealed intra-/interchain Pb•••Pb interactions in the lead(II)-carboxyl chains greatly affected the photochemical output.

Analyses on intracellular Fe3+ with a rhodamine probe: “turn-on” response, specific recognition and bioimaging

“…The maximum fluorescence intensity at 587.0 nm in the Job plot showed that a 1 : 1 stoichiometry 21,22 between J3 and Fe 3+ was adopted (Fig. 5, left).…”

Recent Advances on the Applications of Luminescent Pb2+-Containing Metal–Organic Frameworks in White-Light Emission and Sensing

“…These bulk MOF materials had iso-reticular structures with 1D square or rhombic channels with subtle difference in Pb 2+ coordination geometry. Optical experiments showed that 21 was an excellent white emitter with multiple advantages, including pure white color with the chromaticity coordinates (0.331, 0.347) (λ ex 350 nm), high fluorescence intensity, and good compatibility to human visibility (Yin Z. et al, 2019). Hydrothermal reaction of pyridine-2,6-dicarboxylic acid (H 2 L 12 ) and Pb(NO 3 ) 2 afforded a rhombic-like 2D polymer [Pb(L 12 )] (24) (Qi et al, 2018).…”

Ψ-Polyhedral symbols for coordination geometries of lead(II) with a stereochemically active lone pair

“…This article originates from a rerefinement of a set of lead(II)-MOFs from published crystallographic information files (CIFs) (Yin et al, 2019) because the published refinements used improper restraints that may have resulted in incorrect chemical formulae. A clearer description of the coordination geometry is now presented that gives information on the lone pair.…”