Preparation Of Microporous Crystalline Materials With Weak Interaction Forces For Optical Detection

Optical detection is a commonly used detection method in life.It has the characteristics of high precision,strong sensitivity,but its detection cost is high and the operation is complex.Therefore,it is of great significance to develop detection materials with low cost and simple operation.As a widely used material,microporous crystal materials have the characteristics of diverse composition,high designability of structure and function.Therefore,by constructing microporous crystal materials with different optical detection properties,the detection of p H value and amino acids can be achieved.In this paper,microporous crystal materials are designed and prepared Co-CDI-CO₃^2-,Zn-CPP,Mn-P were selected for optical detection of p H and amino acids in strong acid solutions.The main contents are as follows:（1）In order to visualize the detection of strong acid solution（p H 2.0-2.4）,Co-CDI-CO₃^2-,a microporous crystal material with coordination bond and hydrogen bond coexistence was designed and prepared by mixing Co²⁺and organic molecule N′N-carbonyldiimidazole（CDI）.The experimental results showed that the color of Co-CDI-CO₃^2-changed from pink to purple between p H 2.0-2.4,and the p H value of the solution could be determined by the color change,and the detection accuracy reacheed 0.1.Through the analysis of the detection mechanism,it is indicated that the surface Co²⁺coordination environment of the material will change in the strong acid environment,which will cause the color change of the material to achieve the detection purpose.Co-CDI-CO₃^2-has the characteristics of simple,fast and high yield,and is an ideal material for detecting p H value of strong acids.（2）In order to enhance the interaction between the material and the tested object and improve the selectivity of optical detection of materials,the ligand 2,6-bis（4′-carboxyphenyl）pyridine（H₂CPP）containing N atoms was selected to construct Zn-CPP,a microporous crystal material which containing coordination bonds,hydrogen bonds and van der Waals forces with Zn²⁺.The orderly arrangement of ligand molecules in the crystal structure can not only avoid the quenching of interligand agglomeration with fluorescence effect,but also exposes N atoms,increasing the probability of contact between amino acids and them.Fluorescence detection of twenty-three amino acids（including acidic,alkaline,and neutral amino acids）using Zn-CPP,and the results showed that Zn-CPP had a fluorescence quenching response to tryptophan（Trp）and tyrosine（Tyr）in neutral amino acids,and its detection limits for Trp and Tyr were lower,2.5μM and 4.2μM,respectively.In addition,Zn-CPP can still show a high sensitivity fluorescence quenching response to Trp and Tyr in the presence of other neutral amino acid molecules,indicating that Zn-CPP has excellent selectivity and anti-interference for amino acid detection.According to the linear relationship between Zn-CPP fluorescence intensity and Trp or Tyr concentration,the distinction between the two amino acids can be achieved.Therefore,Zn-CPP,which has good selectivity and anti-interference,can be used as a new type of Trp and Tyr detection materials in amino acids.（3）In order to further investigate the structure-activity relationship between microporous crystal materials and amino acid detection performance,ligands 3,5-bis（4′-carboxyphenyl）pyridine（H₂PBC）and 2,6-bis（4′-carboxyphenyl）pyridine（H₂CPP）were used to construct layered Mn-based isostructural microporous crystal materials Mn-PBC and Mn-CPP with Mn²⁺.Mn-PBC and Mn-CPP were used to fluorescence probe twenty-three amino acids（including acidic,basic and neutral amino acids）to investigate the effect of different N positions in ligands on fluorescence detection performance.The experimental results showed that compared with Mn-CPP,Mn-PBC exhibits fluorescence quenching effect on tryptophan（Trp,detection limit14.6μM）and tyrosine（Tyr,detection limit 30.3μM）in neutral amino acids,indicating that the spatial position of pyridine N atoms in the ligand affects the optical detection performance of the material.In addition,the tooth-like arrangement of ligands in the crystal structure in space is conducive to the exposure of more active sites and enhances selective fluorescence detection of amino acids.Mn-PBC has good selectivity and anti-interference for Trp and Tyr,and can distinguish the two amino acids according to the linear relationship between the fluorescence intensity of Mn-PBC and the concentration of Trp and Tyr.The synthesis of Mn based microporous crystal material series provides a reference for the design and preparation of microporous crystal materials with fluorescence detection performance by studying the detection performance of amino acids.