Two highly stable metal–organic frameworks (MOFs) assembled by a flexible 1,4-bis(2-methylimidazol-1-yl)butane (bib), and two different aromatic carboxylate coligands, namely, [Zn(BDC–OH₂)(bib)] (1) and [Cd₃(BTC)₂(bib)(DMF)₃] (2) (H₂BDC–OH₂ = 2,5-dihydroxyterephthalic acid, H₃BTC = 1,3,5-benzenetribenzoic acid), were designed and synthesized. 1 showed a 4-fold interpenetration of 4-connected dia-type topological net. In 2, the 3D topological structure can be viewed as a (3,4,5)-connected network, and its Schläli point is {4·6²}₂ {4²·6·8³} {4⁶·8⁹}. Different auxiliary carboxylate ligands were examined with respect to the building of various structures. 1 and 2 have outstanding photocatalytic behaviors for the disintegration of methyl violet (MV) under UV irradiation.

The abuse of antibiotics has caused global problems including critical environmental ecology impacts. Herein, four new metal–organic frameworks (MOFs) – {[Cd(HL)(bic)(H₂O)]·2H₂O}(1), {[Cd₃(L)₂(bbi)₂(H₂O)₂]·2H₂O}(2), [Cd₃(L)₂(bib)₂(H₂O)₂] (3) and [Cd₃(L)₂(idy)₂] (4), where bic = 3,6-bis(imidazol-1-yl)-9H-carbazole, bbi = 1,1′-(1,4-butanediyl)bis(imidazole), bib =1,4-bis(1-imidazoly)benzene and idy = 2-imidazol-1-ylpyridine – have been synthesized and fully characterized. 1 is a 1D chain with a large loop, stacked parallel to each other in 2D supramolecular layers by hydrogen-bonded and packing interactions. 2 and 3 are isostructural and show a 3D (3,8)-connected tfz-type network with (4³)₂(4⁶·6¹⁸·8⁴) topology. 4 has a 2D grid framework. The oxygen atom of the ether-bridging group acts as a Lewis base site, which improves the connection strength and allows the detection of 11 types of antibiotics through the fluorescence quenching effect. Among them, 2 exhibits sensitive and selective detection for nitrofural (NZF) (K_SV = 8.26 × 10³ M⁻¹ and LOD = 1.83 ppm). Moreover, the highly selective probe behavior towards NZF ions could be maintained even if there are other interfering antibiotics.

An unexploited pentacarboxylate ligand, 2,5-bis(3′,5′-dicarboxylphenyl)-benzoic acid (H₅L), was designed and used for the preparation of metal organic material using Zn²⁺ as a node. The new compound, {(Me₂NH₂)[Zn₂(L)(H₂O)]·0.5DMF}_n (1) (DMF = dimethylformamide), has been synthesized and structurally characterized. The topology of the 5-connected anionic framework may be described as (4⁴)(6⁶) (Schläfli symbol) based on {M₂(CO₂)₅} molecular building blocks (MBBs) and L ligands in 1. It has been demonstrated that 1 can act as a fluorescent sensor for highly sensitive detection of nitroaromatics and Fe³⁺, with a detection limit of 0.54 ppm for 2,4,6-trinitrophenol (TNP) and 0.81 ppm for Fe³⁺. The possible emission quenching mechanism in the presence of nitroaromatics has been addressed by theoretical calculations.

The precise unification of functional groups and photoluminescence properties can give rise to MOFs that can offer diverse applications like selective detection of nitroaromatic compounds (NACs) which are considered to be an important ingredient of explosive as well as cation and anion sensing. Hence, a new 3D metal-organic framework (MOF) [Cd₂(btc)(bib)(HCOO)(H₂O)·H₂O]_n (1) has been synthesized using mixed ligand strategy by solvothermal reaction of cadmium acetate with two ligands viz. 1,3,5-benzenetricarboxylic acid (H₃btc) and 1,4-bis(2-methyl-imidazol-1-yl)butane (bib). The MOF 1 possesses highly 10-connected network which is based on {Cd₄(btc)₂(bib)₄} molecular building block. The studies showed that 1 could be taken as the fluorescent sensor for sensitive recognition of NACs, in particular 2,4,6-trinitrophenol (TNP) with notable quenching (K_sv = 5.42 × 10⁴ M⁻¹) and LOD of 1.77 ppm. Additionally, 1 also displayed selective sensing for Fe³⁺ ions with K_sv = 6.05 × 10³ M^{− 1} and LOD = 1.56 ppm. Also, this dual sensor displayed excellent reusability toward the detection of TNP and Fe³⁺ ion. Theoretical calculations have been performed to propose the probable mechanism for the sensing luminescence intensity. Calculations indicated that because of the charge transfer and weak interaction that is operating between NACs and MOF, the weakening in the photoluminescence intensity resulted.

Three new d ¹⁰ based MOFs using 5-[bis(3-carboxybenzyl)-amino]isophthalic acid were synthesized and their sensing behavior towards nitroaromatics was evaluated.