Análise estrutural e termodinâmica do composto {[Zn(2,5-­pdc)(H2O)2].H2O}n nas formas desidratada e delaminada

Abstract

Metal-organic frameworks (MOFs) belong to the class of coordination polymers (CPs) and exhibit properties such as porosity and crystallinity. In particular, two­dimensional MOFs have attracted interest in the development of a new generation of optical and electronic devices. The possibility of thin film formation of some of these MOFs makes them more attractive materials. The two­dimensional MOF studied in this work was the network {[Zn(2,5-pdc)(H2O)2].H2O}n (2,5-pdc = 2,5-pyridinedicarboxylate), ZnPDC2D. The MOF 2D was synthesized and characterized by different experimental techniques and was also studied by computer simulation. Two optimized ZnPDC2D structures were obtained by distinct methods (PBE and PBE­-D2) with a good description of their parameters. The structure obtained from the simulation of the dehydration process suggest the formation of three new phases (d1-ZnPDC2D, d2-ZnPDC2D and d3-ZnPDC2D). The temperature at which ZnPDC2D undergoes amorphization was determined by X­ray podwer diffraction measurement with in situ temperature rise and it could be inferred that the amorphous phase undergoes a reversible transformation after being exposed to the environment. The thermodynamics of the first stage of dehydration shows that the PBE functional is adequate to describe the spontaneity of the reaction. The structures are expected to be obtained by X­ray podwer diffraction analysis and refinement by the Rietveld method. Thise work also reports the simulation of the monofilm by the PBE and PBE-D2 methods. The analyses of electronic properties for all th cited structures were performed and discussed according to the processes and changes involved.