Coordination polymers containing azolate ligands to obtain functional MOFs

Author(s)

Daniel de Oliveira Tavares Alves Martins

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2020-01-21

Examining board members

Ana Maria da Costa Ferreira; Sofia Nikolaou; Heloise de Oliveira Pastore

• Advisor: Ana Maria da Costa Ferreira

Abstract

Coordination polymers are an interesting class of inorganic materials due to their versatile structure and a vast number of properties, namely adsorptive, molecular separation or exchange, catalytic, electronic, magnetic and optical, leading to many potential applications. In the last decades, great attention has been drawn to porous coordination polymers, and in this scenario the term metal-organic frameworks, or MOFs for short, is popularly used to address to these systems. MOFs are mainly obtained through self-assembly of metal centres/clusters (the so-called nodes) and organic linkers in one-pot reactions. Azolates, i.e. nitrogen five-membered rings, appear as important ligands because of their rigid structure and different modes of coordination, which may give rise to beautiful structures with promising and desirable properties. Metal-organic frameworks obtained using imidazole, pyrazole, triazoles and tetrazoles are commonly referred to as metal-azolate frameworks (MAFs) and they are distinguished from MOF analogues mainly because of their high thermal and chemical stability, which are very important but challenging properties. The ease of forming highly insoluble products is probably the reason why azolates have not been employed as organic linkers in the synthesis of MOFs before the last decade. This work encompasses mainly the planning, synthesis and characterization of coordination compounds to obtain new metal-organic frameworks. In this scenario copper(II) complexes with different triazole ligands, namely 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 3- amino-1,2,4-triazole-5 carboxylic acid and 1,2,4-triazole-5-carboxylic acid were synthesized. The complexes were obtained by solvothermal conditions, under controlled pressure and high temperature. The isolated materials were characterized by common spectroscopic techniques (IR, diffuse reflectance UV-Vis, EPR), CHN analysis, X-ray diffraction (XRD), thermogravimetric analyses and SQUID magnetometry to give an insight on their structure and composition. Besides, they have their surface area determined by nitrogen adsorptiondesorption isotherms, to assess the porosity. At last, their capacity to adsorb carbon dioxide selectively was also evaluated. (AU)

• FAPESP's process: 17/19071-6 - Studies of metal complexes containing triazole ligantes aiming the obtaining of multifunctional magnetic MOFs
• Grantee: Daniel de Oliveira Tavares Alves Martins
• Support Opportunities: Scholarships in Brazil - Master