image: This review outlines the research progress in the experiment-oriented discovery of new phases or unique properties under high pressure, including phase transition, abnormal compression, PL discoloration and enhancement. Notably, the improvement of PL quantum yield in MOFs could be achieved by pressure-treated engineering and hydrogen-bonding cooperativity effect.
Credit: ©Science China Press
This study is led by Prof. Xinyi Yang and Prof. Bo Zou (Synergetic Extreme Condition High-Pressure Science Center, State Key Laboratory of Superhard Materials, College of Physics, Jilin University).
Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) with highly ordered porous structure, tunable bandgap, large specific surface area and structural diversity, provide an appealing platform for the development of stimulus response, sensing, imaging and optoelectronics. Synergy arises when linkers and inorganic nodes are combined, or when just linkers are present in COFs, and one coordination system can provide multiple emitting centers while energy/charge transfer related emission can endow MOFs/COFs with dimensional fluorescent functionality. In MOFs/COFs, small structural variations often result in larger optical property changes. Thus, clarifying the relationship between structure and PL is a key task to optimize the optical performance. Among various tuning methods, pressure engineering using the diamond anvil cell is a highly powerful in-situ technique, which can efficiently modulate the structural and optical properties of MOFs/COFs. This review summarized the recent results on the structural evolution and optical behavior of MOFs/COFs regulated by high pressure. In addition, the relationship between structure and optical properties under high pressure has been proposed and established.
“Although remarkable breakthroughs and progress have been made in the exploration and modification of the structure and properties about MOFs/COFs using high pressures, the research on the application of MOFs/COFs in the structure elucidation and optical properties after the pressure treatment has still present several challenges. Firstly, synchrotron radiation X-ray diffraction is not accurate enough in obtaining atomic position information of light elements such as C, H, O and it is difficult to obtain the amorphous structural information under high pressures. Another important challenge lies in realizing their practical applications, which requires a large number of samples.” Zou says.
A few suggestions were provided to solve these problems: (1) Further analysis of the structural evolution of samples could be conducted through high-pressure neutron scattering and the pair distribution function. (2) The application of the pressure-treated samples could be expanded in various fields by using a large-volume press to obtain a large number of samples.
See the article:
Pressure effects on metal/covalent-organic frameworks: structural and optical properties
https://doi.org/10.1007/s11426-024-2050-5
Journal
Science China Chemistry