image: A series of forty MOFs demonstrates the vast potential of MOF materials in developing electrochromic materials, that can conveniently control the types, intensity and changing/mixing sequence of two sets of electrochromic colors.
Credit: ©Science China Press
Electrochromic materials for sure start to play a significant role in more runs of modern technologies. They show vast potentials in dimming windows, smart displayers, anti-counterfeiting, adaptive surfaces, etc., owing to their quick, reversible and energy-efficient color change response under external electric stimulus. While most of such materials are pure inorganics/organics, metal-organic frameworks (MOFs), have recently emerging in the field. Constructing from metal ions/nodes and organic linkers, the framework-like molecular architecture of MOFs allows periodic arrangement of functional sites, with huge designability as of LEGOs.
Back to electrochromism, pioneering works have established several MOFs as potential candidates to modern technologies. However, admittedly, it is far less compared to other well-known applications of MOFs such as catalysis, sensing and adsorption/separation. There is also a lack in tactics on precisely controlling their electrochromic behavior to satisfy the increasing complexity of modern electronics. And this is where the following research project heads for.
Researchers from Nankai University (China) led by Prof. Jiandong Pang and others propose a new electrochromic MOF platform based on the NDI-containing primary linker (R-linkers that introduce “color 1”; NDI = naphthalene diimide) and linear auxiliary linkers (X-linkers that introduce “color 2”). Rather than mixing two electrochromic materials in particle form, this platform offers molecular-level mixture of electrochromic cores within one solid-state material, and allows multidirectional tuning of the electrochromic behaviors, including:
- Changing the types of the R-group to alter the strength (or depth) of “color 1”.
- Changing the types of X-linkers to alter the types of “color 2”.
- Changing the MOF topology to alter the amount of X-linkers within the MOFs, which equals to altering the strength (or depth) of “color 2”.
Considering the generic synthetic conditions of all these MOFs as well as a good extensibility regarding R-/X-linkers, this work shall provide a unique perspective on developing future smart electronics. The results are published in National Science Review (DOI: 10.1093/nsr/nwaf326).