Researchers regulate microenvironment in boron-imidazolate frameworks to enhance CO₂ electroreduction to C₂H₄

Crystalline boron imidazolate frameworks (BIFs) are a lightweight zeolite-like metal-organic framework (MOF) developed to simulate the zeolite molecular sieve structure. BIFs contain both covalent bonds (B–N) and metal coordination bonds (M–N). Therefore, it is also regarded as a unique family of materials between MOFs and covalent organic frameworks (COFs).

In a study published in Chemical Communications, Prof. Zhang Jian and Prof. Zhang Haixia from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences, constructed a series of isostructural two-dimensional (2D) BIFs by using the second carboxylic ligands with similar structure to adjust the coordination microenvironment, converting CO₂ to ethylene (C₂H₄) by electrocatalytic reduction.

Using the structure-induced effect of KBH(mim)₃ ligand, four crystals (BIF-151 to BIF-154) with identical body framework and metal coordination environment were constructed. Four types of monocarboxylate ligands with different substituent elements and substituent positions could be used as dangling ligands to modify these layers.

These four crystals have good stability in different pH and solvents. Further electrocatalytic results indicated that all four crystals demonstrate catalytic activity towards CO₂RR, especially with certain selectivity towards C₂H₄ products. However, the activity and selectivity toward C₂H₄ were distinctly different.

These findings suggest that catalytic activity and selectivity are not solely contingent upon the active metal site but are also influenced by the surrounding ligand environment, including factors such as the composition and spatial arrangement of substituent elements.

Additionally, the researchers synthesized a series of microenvironment-regulated boron BIFs, emphasizing the significance of the coordination environment in the electrocatalytic reduction of CO₂.

This study offers a novel approach to enhance the C₂H₄ conversion rate.