Pore engineering via controlled decomposition of counter cations in an anion-based metal-organic framework
image: Schematic illustration of the pore engineering strategy in Y-ebdc. In its initial state, dimethylamine (DMA) cations within the pores of Y-ebdc act as "gatekeepers," effectively blocking C3H8 while allowing C3H6 to pass, thus exhibiting high selectivity. However, the occupation of pore volume by DMA also limits its adsorption capacity. Following the partial removal of DMA via controlled thermal decomposition, the material's aperture size and pore volume are enlarged. This optimized pore structure maintains the original high selectivity while significantly accelerating C3H6 adsorption, ultimately leading to a remarkable enhancement in its dynamic uptake capacity.
Credit: Nano Research, Zhengzhou University
The separation of propylene (C3H6) from propane (C3H8) is essential for producing polymer-grade C3H6, but it remains one of the most energy-intensive separations in the chemical industry due to the nearly identical molecular sizes of the two gases. Advanced solid adsorbents like metal-organic frameworks (MOFs) offer a promising energy-efficient alternative, but researchers often face a trade-off between gas uptake capacity and selectivity.
A team of researchers led by Associate Researcher Guanying Dong and Prof. Yatao Zhang from Zhengzhou University has developed a highly effective strategy to overcome this challenge. They designed a new yttrium-based MOF, Y-ebdc, with cage-type structures that accommodate protonated dimethylamine (DMA) cations. These DMA cations act as both counter cations and molecular sieving gates that can be precisely controlled.
The team published their findings in the journal Nano Research on January 31, 2026.
"In anionic MOFs, organic counter cations offer a highly effective way to optimize separation performance because they act as 'gatekeepers' that selectively obstruct the channels," explained Prof. Yatao Zhang, a corresponding author of the study. "Our work focused on not just including these gatekeepers, but on precisely regulating them through a simple thermal decomposition process to find the 'sweet spot' for separation."
Metal-organic frameworks (MOFs), also known as porous coordination polymers (PCPs), represent a compelling choice in adsorptive gas separation in light of their high degree of predictability and tunability on pore size and functionality. Cage-type MOFs are characterized by their narrow windows and large cavities, a unique structural feature that enables them to serve as sieves while simultaneously providing rapid diffusion channels. This dual capability holds significant promise for overcoming the trade-off between capacity and separation selectivity.
The team achieved subsequent optimization of the adsorption separation performance for C3H6/C3H8 was achieved through regulation of DMA’s thermal decomposition. "We discovered that by heating the material to 300oC, we could remove approximately 70% of the DMA cations," said Associate Researcher Guanying Dong, another corresponding author. "This partial removal expanded the aperture window and increased the pore volume. The result was a remarkable boost in the dynamic C3H6 uptake, while the material retained its excellent molecular sieving capability to exclude C3H8."
The optimized material, Y-ebdc-300, demonstrated a dynamic C3H6 capacity of 1.66 mmol g-1, surpassing many other top-performing molecular sieve adsorbents. Crucially, it facilitated the direct production of polymer-grade (>99.5%) C3H6 in a single adsorption-desorption cycle, highlighting its potential for practical industrial application. The material also showed excellent stability, maintaining its performance over five cycles.
This study exemplifies how engineering the pore environment via co-existing counter cations within MOFs can effectively boost gas adsorption and separation performance, offering instructive guide for continuous optimization of the function of MOF materials for adsorption separation.
Other contributors include Zongkai Liu, Bingquan Hua, Tianyou Lu, and Xiaoquan Feng from the school of Chemical Engineering at Zhengzhou University in Zhengzhou, China; and Jingwei Hou from the school of Chemical Engineering at the University of Queensland St Lucia, QLD 4072, Australia.
This work was supported by the National Natural Science Foundation of China (NO. 22208318), the Science and Technology Innovation Leading Talent Support Program of Henan Province (254200510023), and the Science and Technology Research Project of Henan Province (252102231025).
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.