A new polydentate tetracarboxylic acid with a benzothiadiazole unit (4',4'''-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1'-biphenyl]-3,5-dicarboxylic acid), H4BTDBA) has been used to prepare a pH-stable three-dimensional TbIII-based metal-organic framework (MOF) with the formula {[(CH3)2NH2]0.7[Tb2(BTDBA)1.5(lac)0.7(H2O)2]·solvents}n (Hlac = lactic acid, JXUST-19). JXUST-19 exhibits a new (4,4,12)-connected topology based on tetranuclear [Tb4] clusters. JXUST-19 can remain stable when soaked in water for at least 1 week and in aqueous solutions with various pH values (2-12) for 24 h. Fluorescence study indicates JXUST-19 can be employed as a rare turn-on and blue-shift MOF sensor toward benzaldehyde (BZ) and salicylaldehyde (SA). To date, JXUST-19 represents the first TbIII-based turn-on MOF sensor toward salicylaldehyde in aqueous solution, and the fluorescence enhancement and naked-eye detection of BZ have been rarely reported. In addition, JXUST-19 based fluorescent test papers, light-emitting diode lamp beads, and portable composite films were developed to realize naked-eye detection of BZ and SA, which has great potential in practical applications.

A pH-Stable TbIII-Based Metal-Organic Framework as a Turn-On and Blue-Shift Fluorescence Sensor toward Benzaldehyde and Salicylaldehyde in Aqueous Solution.

Due to their important role in biological systems, it is urgent to develop a material that can rapidly and sensitively detect the concentration of Fe3+ and Al3+ ions. In this work, a brand-new CdII-based metal-organic framework [Cd(BTBD)2(AIC)]n (JXUST-18, BTBD = 4,7-bis(1H-1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole and H2AIC = 5-aminoisophthalic acid) with a 4-connected sql topology was designed and synthesized. The symmetrical CdII centers are linked by AIC2- ligands with μ3-η1:η1:η1:η1 coordination mode to form a [Cd2(COO)2] secondary building unit (SBU). The contiguous SBUs are further connected by BTBD ligands to form a two-dimensional (2D) layer structure. JXUST-18 can remain stable in aqueous solutions with pH values of 3-12 or in boiling water. Luminescent experiments suggest that JXUST-18 displays more than eightfold fluorescence enhancement in the presence of Fe3+ and Al3+ ions, and the detection limits for Fe3+ and Al3+ ions are 0.196 and 0.184 μM, respectively. Furthermore, the change in luminescence color is uncomplicatedly distinguishable with the naked eye under ultraviolet light at 365 nm. In addition, a series of devices based on JXUST-18 including fluorescence test strips, lamp beads, and composite films were developed to detect metal ions via visual changes in luminescence color. Significantly, JXUST-18 is a rare MOF-based turn-on fluorescence sensor for the detection of Fe3+ ions. The theoretical calculation suggests that the complexation of Fe3+/Al3+ ions and the -NH2 group contributes to fluorescence enhancement.

Fabrication and DFT Calculation of Amine-Functionalized Metal-Organic Framework as a Turn-On Fluorescence Sensor for Fe3+ and Al3+ Ions.

A novel CdII-based two-fold interpenetrated metal-organic framework (MOF), namely {[Cd2(BTDB)2(4,4-bpy)]·DMF}n (JXUST-14), (H2BTDB = 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid and 4,4-bpy = 4,4-bipyridine), has been prepared and characterized. Single-crystal structure determination reveals that JXUST-14 has a tetranuclear cluster based 6-connected pcu topological network with Schlafli symbol {412·63}. When soaked in common organic solvents and aqueous solutions with diverse pH values of 2-12 for 48 h, JXUST-14 remains stable. JXUST-14 is a highly selective and sensitive luminescent sensor for L-histidine (His) with a detection limit of 11.1 ppm. JXUST-14 is the first CdII-based MOF for the detection of His via turn-on and fluorescence blue-shift effects. Experimental study and theoretical calculation suggest that the sensing process can be mainly attributed to a charge transfer and energy transfer mechanism. More interestingly, LED lamps of JXUST-14 and JXUST-14@His were successfully developed, which endowed efficient sensitivity for His detection and thus provide great potential for future applications.

Turn-on and blue-shift fluorescence sensor toward L-histidine based on stable CdII metal-organic framework with tetranuclear cluster units.

Efficient luminescence sensor is judged as one most up-and-coming cure to combat environmental pollution. By combining precise structures and defined functional sites, luminescent coordinated metal clusters (LCMCs) can allow mechanism-based...

A {Zn4} cluster as a bi-function luminescence sensor for highly sensitive detection of chloride ion and histidine in aqueous media

A family of novel lanthanide-based metal-organic frameworks (Ln-MOFs) with bifunctional fluorescence sensing, namely {[(CH3)2NH2]5[Ln5(TBAPy)5]•solvent}n (Ln = Gd (1), Tb (2), and Dy (3), H4TBAPy = 1,3,5,7-tetra(4-carboxybenzene)pyrene), have been synthesized and...

Lanthanide-based metal-organic framework materials as bifunctional fluorescence sensors toward acetylacetone and aspartic acid

Recently, single-crystal-to-single-crystal conversion has been a hot topic in the field of metal-organic framework (MOF) materials, which could improve the stability and properties due to the structural change. A new...

Temperature- and solvent-induced reversible single-crystal-to-single-crystal transformations of TbIII-based MOFs with excellent stabilities and fluorescence sensing properties toward drug molecules

Luminescent metal–organic frameworks (LMOFs) have become a promising class of fluorescence sensing materials, however, the multi-responsive LMOF sensors for organic compounds are rather rare. Herein, a water stable and highly efficient luminescent MOF with the formula of {[Zn(BBZB)(2,6-NDC)]·solvents}n (JXUST-10, BBZB = 4,7-bis(1H-benzimidazole-1-yl)-2,1,3-benzothiadiazole and 2,6-NDC = 2,6-naphthalenedicarboxylate) was constructed by the incorporation of Zn2+ and two organic ligands (BBZB and 2,6-NDC) featuring the conjugate system. JXUST-10 is a three-dimensional two-fold interpenetrated framework with good fluorescent property. Based on the luminescent characteristic, JXUST-10 can be used as a multi-responsive sensor for detection of three different analytes including tetracycline, benzaldehyde and uric acid via different luminescent change behaviours. Remarkably, fluorescence test paper and LED light devices are used to detect analytes through the visual change of luminescence colour of JXUST-10 from blue greenish to yellow greenish under ultraviolet light (365 nm) irradiation. Furthermore, the probable sensing mechanisms for three target analytes were also discussed. Appendix S1: Supporting Information Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. 

A Highly Efficient Luminescent Metal–Organic Framework with Strong Conjugate Unit for Sensing Small Molecules

A stable metal-organic framework with the formula {[Co(BBZB)(IPA)]·H2O}n (JXUST-23, BBZB = 4,7-bis(1H-benzimidazole-1-yl)-2,1,3-benzothiadiazole and H2IPA = isophthalic acid) was constructed by incorporating Co2+ ions and two conjugated ligands under solvothermal conditions. JXUST-23 takes a dinuclear cluster-based layer structure with a porosity of 2.7%. In this work, JXUST-23 was used to activate peroxymonosulfate (PMS) to degrade rhodamine B (RhB), a difficult-to-degrade pollutant in water. Compared with pure PMS or JXUST-23, the JXUST-23/PMS system displays the best degradation ability of RhB in neutral solution. When the mass ratio of JXUST-23 to PMS was 2:3, 99.72% of RhB (50 ppm) was removed within 60 min, and the reaction rate was 0.1 min-1. Furthermore, free radical quenching experiments show that SO4•- was the main free radical during the process of RhB degradation. In addition, JXUST-23 exhibits good reusability for the degradation of the organic dye RhB, making it a potential candidate for environmental remediation.

Bi-Lian Chai

Papers

Temperature- and solvent-induced reversible single-crystal-to-single-crystal transformations of TbIII-based MOFs with excellent stabilities and fluorescence sensing properties toward drug molecules

A Highly Efficient Luminescent Metal–Organic Framework with Strong Conjugate Unit for Sensing Small Molecules

Enhanced Heterogeneous Catalytic Activity of Peroxymonosulfate for Rhodamine B Degradation via a CoII-Based Metal-Organic Framework.