Dan Yue

Ratiometric dual-emitting MOF⊃dye thermometers with a tunable operating range and sensitivity

A tetracarboxylic acid ligand containing a highly polarized benzothiadiazole moiety was designed and used to construct the luminescent porous MOF ZJU-21, which can efficiently absorb the luminescent dye 4-[p-(dimethylamino)styryl]-1-methylpyridinium (DMASM) into the pores as well as sensitize it, yielding a dual-emitting MOF⊃dye composite ZJU-21⊃DMASM. The emission color of the resulting composite can be modulated by controlling the amount of dyes, and the intensity ratio of the two emissions can be used as a ratiometric thermometric parameter for temperature measurement. ZJU-21⊃DMASM also exhibits excellent temperature-dependent photoluminescence properties in the physiological temperature range, which, as well as the temperature and sensitivity ranges, can be tuned by controlling the concentration of DMASM in the pores of the host framework. Moreover, the proposed scheme can be readily applied to other luminescent porous MOFs and organic dyes, thereby providing a new perspective for the design of MOF⊃dye ratiometric temperature sensors.

A highly stable amino-coordinated MOF for unprecedented block off N2 adsorption and extraordinary CO2/N2 separation

A highly stable amino-coordinated metal-organic framework ZJU-198 has been synthesized and structurally characterized, exhibiting high CO2 uptake of 105.8 cm3 cm-3 while blocking off N2 adsorption at 1.0 bar and 298 K, attributed to the unique pore window sizes.

Ratiometric luminescence sensing based on a mixed Ce/Eu metal–organic framework

Ascorbic acid (AA), which is a well-known antioxidant, reacts with reactive oxygen species (ROS) inside the human body. It is crucial for the proper functioning of living organisms, however, the sensing of AA is still a huge challenge. Herein, a mixed Ce/Eu metal–organic framework [ZJU-136-Ce1−xEux (x = 0.24, 0.36)] is designed and synthesized. Due to the specific redox reaction between the enediol group of AA and Ce4+, the fluorescence intensity of the ligand increases significantly with a simultaneous fluorescence quenching of Eu ions, resulting in a ratiometric fluorescent probe for detecting AA. It is worth noting that the ZJU-136-Ce1−xEux (x = 0.24, 0.36) exhibited good luminescence properties and ratiometric fluorescence for AA determination. Furthermore, the regeneration cycle test shows that the mixed Ce/Eu metal–organic framework can be used as a potential ratiometric sensor for AA determination.

Flexible Metal–Organic Framework‐Based Mixed‐Matrix Membranes: A New Platform for H2S Sensors

Metal-organic framework (MOF)-polymer mixed-matrix membranes (MMMs) have shown great potential and superior performance in gas separations. However, their sensing application has not been fully established yet. Herein, a rare example of using flexible MOF-based MMMs as a fluorescent turn-on sensor for the detection of hydrogen sulfide (H2 S) is reported. These MOF-based MMMs are readily prepared by mixing a highly stable aluminum-based nano-MOF (Al-MIL-53-NO2 ) into poly(vinylidene fluoride) with high loadings up to 70%. Unlike the intrinsic fragility and poor processability of pure-MOF membranes, these MMMs exhibit desirable flexibility and processability that are more suitable for practical sensing applications. The uniform distribution of Al-MIL-53-NO2 particles combined with the permanent pores of MOFs enable these MMMs to show good water permeation flux and consequently have a full contact between the analyte and MOFs. The developed MMM sensor (70% MOF loading) thus shows a highly remarkable detection selectivity and sensitivity for H2 S with an exceptionally low detection limit around 92.31 × 10-9 m, three orders of magnitude lower than the reported powder-form MOFs. This work demonstrates that it is feasible to develop flexible luminescent MOF-based MMMs as a novel platform for chemical sensing applications.

A luminescent turn-up metal–organic framework sensor for tryptophan based on singlet–singlet Förster energy transfer

A water stable metal-organic framework, ZJU-108, was designed and successfully synthesized as a luminescent turn-up sensor, and it can discriminate tryptophan from other natural amino acids in aqueous solution. Because of the apparent lower singlet level of tryptophan compared with other amino acids, the singlet-singlet Förster energy transfer mechanism was applied to design a luminescent sensor. As a result, a selective MOF sensor for tryptophan was realized by choosing the ligand with the appropriate singlet energy level. As expected, ZJU-108 shows an excellent luminescence enhancement response to tryptophan over other natural amino acids with a detection limit of 42.9 nM. This work presents a new insight for designing turn-up MOF sensors and demonstrates the potential of ZJU-108 as a luminescent probe for the detection of tryptophan.