A novel metal‐organic framework (MOF) assembled by a semi‐rigid tricarboxylate, namely, 5‐(3,4‐dicarboxylphenoxy) nicotic acid (H3L) has been solvothermally synthesized: [Zn3(L)2(H2O)2] ⋅ 3H2O 1. Single‐crystal X‐ray diffraction analysis indicates that MOF 1 shows 2‐D layer with quadrangle channels along the a axis (ca. 7.0×8.3 Å2). The 2‐D layer self‐assembles into a final 3‐D supramolecular network via the interlayer π⋯π interactions. The photoluminescence investigations indicate that 1 can selectively and sensitively detect acetylacetone (acac) with high KSV value of 3.597×104 M−1 and low limit of detection (LOD) of 50.77 ppb. Further mechanism studies have shown that static photo‐competitive absorption, photoinduced electron transfer and H‐bonding interaction between chemosensor and the analyte may be the primary causes of the fluorescence quenching effect for acac.

The optical absorption spectra seen at room and cryogenic temperatures in green-colored Np:CaF2 crystals have been attributed to Np3+ substitution at Ca2+ [000] sites with three distinct modes of charge compensation and correspondingly lowered local symmetries. These are: A, C3v symmetry associated with the presence of an F− compensator at empty [(1/2)(1/2)(1/2)]-type sites; B, C3v symmetry related to the replacement of a nn F− at a [(1/4)(1/4)(1/4)]-type position by O2−; C, C4v symmetry attributed to the presence of an F− compensator at empty [00(1/2)]-type sites. A two-parameter fit to the five lowest excited multiplet centers yielded the following F2 and ζ values (in cm−1): A, 214.5 and 2032; B, 212.7 and 2001; C, 219.1 and 2083. The multiplet splittings of each of these three spectra have been fit with crystal potential (’’crystal-field’’) parameters. Fluorescence, consisting of several broad bands near 1.4 μm and four lines near 2.5 μm, was associated with the Np3+ type-C sites. At liquid He temperature, the 2.5 μm spectrum consisted of just one sharp line at 3929 cm−1. Vibrational effects were largely absent, both in absorption and fluorescence.