Synthesis,Structures And Properties Of Porphyrin-Based Biological Metal-Organic Frameworks

Biological Metal-Organic Frameworks?BioMOFs?are a class of crystalline porous materials with biomimetic features.Due to its excellent biocompatibility,structural diversity,tunable pore size,and modifiable surface,it provides a good platform for studying the interaction between host and guest of biomolecules in its confined spaces.In addition,it shows potential prospects in many biological research fields such as biomimetic catalysis,fluorescence sensing,and biopharmaceuticals.Porphyrins and metalloporphyrins are important components of living organisms,and their main role in life is to support aerobic activities.To mimic this biological process,supramolecules with porphyrins as building blocks have demonstrated a wide range of applications in this regard.The porphyrin-based porous materials possess both the porosity of the frameworks and the physiological and chemical activities of the porphyrin compounds,which have been frequently studied in adsorption and separation,catalysis,sensing,drug carriers and so on.In this work,a series of three-dimensional porphyrin-based BioMOFs were constructed by solvothermal reactions of nucleobase adenine or its derivatives,metalloporphyrincarboxylic acid,and Zn?II?salt in DMF solutions.And their applications,such as fluorescence sensing,gas adsorption and separation,were extensively studied.In the first chapter,we report two porphyrin-based BioMOFs?named as ZnTCPPAZn and FeTCPPAZn?synthesized by using adenine and different metallated porphyrins,both of which exhibit excellent thermal and chemical stability.Due to the metallation of the porphyrin,significant differences in gas adsorption and separation are observed.Compared with FeTCPPAZn,the adsorption capacity of CO₂ and C₂H₆ on ZnTCPPAZn is greatly improved.In addition,the separation selectivity of equimolar C₂H₆/CO₂ for ZnTCPPAZn is calculated to be6.47².43 in favor of C₂H₆ over the entire pressure range,which is two times the separation selectivity of FeTCPPAZn?3.00⁰.99?under the same conditions.Thus,the high selectivity of gas mixtures can be achieved by modulating the porphyrin metal center,which provides a new route for the synthesis of high-performance MOF for gas separation.In the second chapter,we report a flexible luminescent BioMOF?named as ZnTCPPA-NH₂Zn?of which the zinc dipaddlewheel clusters can undergo deformation with the change of surrounding environment,and exhibit reversible switching between as-synthesized"open"phase?ZnTCPPA-NH₂Zn-??,activated"closed"phase?ZnTCPPA-NH₂Zn-??,and a"semi-closed"intermediate phase?ZnTCPPA-NH₂Zn-??.Interestingly,the luminescence properties of ZnTCPPA-NH₂Zn vary with the switching of the flexible framework.The phase transformation from ZnTCPPA-NH₂Zn-?to ZnTCPPA-NH₂Zn-?enables rapid fluorescence response to small-sized polar protonic VOC vapors such as methanol and ethanol,both of which can induce the phase transformation by coordiation to the central.This work provides an interesting example for synthesis of flexible MOFs as fluorescence sensor.