Design,Preparation,and Properties Modulation Of Luminescent Metal-organic Frameworks For Self-Calibrating Temperature Sensing

Temperature is an important physical parameter in human life as well as all fields of natural science,its accurate measurement is thus of great importance in human and scientific development.Compared to the traditional contact thermometers,the dual-emitting self-calibrated thermometry technique has attracted extensive attention because of their unique characteristics,including fast response,noninvasiveness,high sensitivity and spatial resolution,as well as applicability in fast-evolving conditions,strong electromagnetic fields,and at submicron scale.Metal-organic frameworks(MOFs),which represent a unique class of hybrid materials,are well known for their intriguing topology,permanent porosity,and tuneable luminescence properties.They have shown great promise for the ratiometric temperature sensing.Although a number of promising ratiometric luminescent thermometers have been developed based on the dual-emitting MOF approach,the ways of modulating the sensing properties of suchsystems have not been explored.In this dissertation,we have developed different mixed-lanthanide Tb/Eu-MOF systems by rational design of organic linkers with suitable triplet excited state(T1)and presented the relationship between the ligand's T1 and the sensing properties of the Tb/Eu-MOF thermometers;We constructed two types of NIR luminescent Nd/Yb-MOFs with different spatial distributions of lanthanide centres by utilizing the organic linkers with different sizes and proposed a method to improve the efficiency of energy transfer from Nd3+ to Yb3+ ions,namely by taking into consideration of their spatial distance,which can modulate the sensing range of Nd/Yb-MOFs thermometer.We have developed a novel ratiometric dual-emitting MOF(?)dye composite,whose temperature sensing range and sensitivity can be modulated by controlling the concentration of the guest dyes.In order to improve the T1 energy of the organic ligand,we developed a new linker 2'-fluoro-[1,1':4',1"-terphenyl]-3,3",5,5"-tetracarboxylic acid(H4FTPTC)with the T1 energy of 24037 cm-1 by incorporating the 1,4-dibromo-2-fluorobenzene group into the prototype ligand[1,1':4',1"-terphenyl]-3,3",5,5"-tetracarboxylic acid(H4TPTC).Based the linker H4FTPTC and lanthanide salts,we constructed a novel Tb/Eu-MOF Tb0.95Eu0.05FTPTC,which can be used as a ratiometric thermometer for temperature measurement in the cryogenic range of 25 to 125 K,with high relative sensitivity.We also demonstrated that the sensing temperature range of such systems cannot be modulated by primitively changing the Tb3+/Eu3+ ratio in the framework.This work therefore provides a new guideline for developing Tb/Eu-MOF thermometers for cryogenic temperature sensing.To verify that the incorporated organic ligand with different T1 can indeed affect the operating range of the Tb/Eu-MOF thermometers,we selected the 6-(4-carboxyphenyl)nicotinic acid(H2CPNA,T1 = 22594 cm-1)and[2,2'-bipyridine]-5,5'?dicarboxylic acid(H2BYPDC,T1 = 24658 cm-1)as ligands to construct two isostructural MOFs Tbi-xEuxCPNA and Tbi-xEuxBPYDC.The ligand H2BYPDC with a high T1 can effectively reduce thermal activation of nonradiative decays with increase of the temperature,and can sustain effective sensitization for Tb3+ and Eu3+ ions through the Foster resonance energy transfer mechanism,which can be expect to enhance the temperature-dependent luminescence performance of as-synthesized Tb/Eu-MOFs.As a result,the temperature sensing range of Tbi-xEuxCPNA was found to be 25-125 K,and that of Tb1-xEuxBPYDC is extended to 25-225 K,demonstrating that incorporating the ligand with a higher or lower T1 energy into the framework can modulate the temperature sensing range of Tb/Eu-MOFs.Since the spatial distance can affect the energy transfer between the Nd3+ and Yb3+ions,we selected two carboxylate ligands,[1,1'-biphenyl]-3,3',5,5'-tetracarboxylic acid(H4BPTC)and H4TPTC,which show different size,as organic linkers to construct two types of NIR luminescent MOFs Nd0.7Yb0.3BPTC and Nd0.5 Yb0.5 TPTC with different spatial distribution of lathanide ions.Compare to the Nd0.7 Yb0.3BPTC,the Ndo.5Ybo.5TPTC with a more uniform and longer Nd3+-Yb3+ centre distance(5.627 A),which can sustain the efficient phonon-assisted energy transfer from Nd3+ to Yb3+ ions with the increasing of temperature and can be expect to extent the temperature operating range.As a result,Nd0.5 Yb0.5 TPTC shows excellent temperature-dependent photoluminescence properties in the physiological temperature range of 25 to 55?,with high relative sensitivity.This work thus provides a new approach for developing Nd/Yb-MOF thermometers for physiological temperature sensing.A tetracarboxylic acid ligand,5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid,which containing a highly polarized benzothiadiazole moiety was designed and used to construct the microporous luminescent MOF ZJU-21,which can efficiently absorb the luminescent 4-[p-(dimethylamino)styryl]-1-methylpyridinium(DMASM)into the pores as well as sensitize it,forming a dual-emitting composite ZJU-21(?)DMASM.It exhibits excellent temperature-dependent photoluminescence properties in the physiological temperature range,which like the temperature and sensitivity ranges can be tuned by controlling the concentration of DMASM in the pores of the host framework.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.