Periodic Reporting for period 1 - CO2COFs (New Heterogeneous Catalyst Materials for Hydrogenation of CO2 to Formic Acid: Metallophthalocyanine-Based 2D- and 3D Covalent Organic Frameworks)
Reporting period: 2019-07-01 to 2022-06-30
The aim of the project was to develop a toolbox of metallophthalocyanine (MPc) building blocks as catalytically active single sites and linkers for the preparations of different 2D and 3D covalent organic framework (COF) materials. By developing single atom catalyst materials, the utilization of the metal catalyst can be maximized, decreasing the amount of critical raw materials used. The developed materials were investigated for their electrocatalytic activity towards oxygen evolution reaction (OER). It is an important anodic half-reaction in electrochemical processes, such as water splitting and CO2 reduction. Water splitting, producing oxygen and hydrogen, is a cornerstone in transforming our fossil fuel based society towards the use of more sustainable chemicals and fuels in the future. However, OER is the rate limiting electrochemical reaction in water splitting due to its sluggish kinetics, and therefore, the development of more active and stable electrocatalysts is a key challenge.
Although noble metal oxides, such as RuO2 and IrO2, have been demonstrated to have high electrocatalytic activities towards the OER, the high price and scarcity of these materials are the major bottlenecks for their practical applications. Therefore, it is of great importance to develop OER electrocatalysts that are efficient, stable and low-cost, and to this end, earth-abundant transition metal-based (eg. Fe, Ni, Co) catalysts are of high interest.
Although noble metal oxides, such as RuO2 and IrO2, have been demonstrated to have high electrocatalytic activities towards the OER, the high price and scarcity of these materials are the major bottlenecks for their practical applications. Therefore, it is of great importance to develop OER electrocatalysts that are efficient, stable and low-cost, and to this end, earth-abundant transition metal-based (eg. Fe, Ni, Co) catalysts are of high interest.
This project developed a synthetic strategy to a series of novel MPc-containing COFs with different TM loadings. Metal-free and metalated (Ni, Fe,) phthalocyanine building blocks were prepared and used with commercial linkers as starting materials in the COF synthesis. To obtain bimetallic catalyst materials, two alternative strategies were developed: one-step method in which two different MPcs and linker molecules were used to prepare the COFs and post-synthetic modification of the COF materials with another catalytically active metal. Electrocatalytic activity of the synthesized COFs was measured towards OER under alkaline conditions, and they reached overpotentials of 410430 mV at current densities of 10 mA cm–2. Ni-containing COF showed catalytic activity among the best of Ni-bearing organic polymers. Moreover, the COF catalysts showed stable performance during 100 h stability test at the current density of 10 mA cm2. The results of the project were presented in an international scientific conference and in a scientific research article.
We developed a credible procedure to prepare metal-free and metalated Pcs and used them as starting materials in the synthesis of novel and stable COF materials, offering a scaffold to periodically place TMs into the materials. Assembling MPcs as single-site molecules into highly ordered and porous structure of COFs ensures highly independent, isolated, and stable active sites and their periodical dispersion in the framework. Despite these advantages of MPc-based COFs, only few have been reported so far and thus, the project was able to expand the toolbox of solution-stable MPc-based COF materials. The prepared frameworks showed electrocatalytic activity among the best of Ni-containing organic polymers in OER, making these noble-metal-free MPc-based COFs credible electrocatalyst option for water splitting and offering a way to contribute to decarbonization of society.