This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Chemical separation can be energy-intensive when molecules have similar sizes and properties. Researchers from Shibaura Institute of Technology, Japan, have now developed an interlayer adaptive crystal that changes its spacing to recognize specific molecules.
The crystal showed appreciable CO2 uptake at pressures as low as 2.0 Pa (195 K) and selectively separated CO2 from nitrogen and methane at 303 K, even under highly humid conditions. It also preferentially captured benzene over several similar molecules, offering a new approach to molecular separation. Chemical separation is among the most energy-intensive operations in modern industry, with separation processes such as distillation estimated to account for approximately 10–15% of global energy consumption, creating a need for efficient approaches to carbon capture and purification.
Conventional porous materials often rely on pore size and adsorption strength, which can struggle to distinguish molecules with similar dimensions. The researchers therefore explored whether a crystal could adapt its internal space to incoming molecules. Addressing this challenge, a research team led by Professor Akiko Hori, together with graduate students Masahiro Abe and Tomoki Jitsukata from Shibaura Institute of Technology, Japan, and Professor Ryotaro Matsuda from Nagoya University, Japan, developed an interlayer adaptive crystal (LAC).
The material is made of thin layers that can move apart when certain molecules approach. Their findings are published in the journal Angewandte Chemie International Edition. "Rather than relying only on molecular size, we focused on the characteristic negative quadrupole moment of CO₂ and sought to use electrostatic complementarity as a new principle for selective separation," says Hori.
"The layered crystal unexpectedly showed that its interlayer space could expand in response to guest molecules." In its guest-free state, the crystal contains ultramicropores measuring about 2.6 Å across. These spaces are too small to serve as conventional pathways for CO₂, yet they act as triggers. Fluorinated aromatic surfaces create positively polarized regions that favor molecules with complementary electrostatic distributions.
When a suitable guest approaches, the layers move apart, allowing larger molecules to enter. This adaptive behavior was especially striking for CO₂. At 195 K, appreciable CO₂ uptake was observed at pressures as low as 2.0 Pa, reaching about 0.2 molecules per [Zn(L)Py]₂ unit at 26 Pa and about 2.0 molecules per unit at 98 kPa.
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