Scientists build high-performance hydrogen separation membranes with "mortar-and-brick" design

As the world transitions towards clean energy, efficient hydrogen purification is paramount. Conventional polymer membranes for gas separation often face a trade-off between permeability and selectivity. While membranes made from crystalline porous materials (CPMs) show great promise, their fabrication typically requires complex procedures.

A research team led by Professors Daofeng Sun and Zixi Kang at China University of Petroleum (East China) has made a significant breakthrough. They have developed a simple "bricks-placing and mortar-pouring" solution-processing strategy to create a novel metal-organic framework/hydrogen-bonded organic framework (MOF/HOF) all-nanoporous composite (ANC) membrane. The study was published in the journal “Nano Research”.

"We can think of MOF nanosheets as 'bricks', first stacked orderly. Then, the HOF monomer solution is poured in like 'mortar', filling the gaps between the bricks and crystallizing to form a dense, defect-free composite membrane," explained Professor Daofeng Sun, senior author of the study. "The key is that the MOF brick surfaces effectively induce the HOF mortar to nucleate preferentially on them, enabling the formation of a continuous membrane even at low monomer concentrations."

The critical innovation lies in using MOFs as hetero-nucleation sites to precisely control HOF crystallization, which is evidenced by the influence from different morphology and size of MOFs on HOFs’ solution-processing. By systematically optimizing parameters like HOF monomer concentration and solvent evaporation temperature, the researchers suppressed unwanted homogeneous nucleation of HOF and promoted beneficial heterogeneous nucleation on MOF surfaces. This achieved a balance between nucleation driving force, molecular attachment rate, and nutrient supply-and-demand.

The optimized composite membrane demonstrated exceptional hydrogen separation performance. "Compared to the pristine HOF membrane, our best ANC membrane exhibited a 562% enhancement in hydrogen permeance, alongside a 241% improvement in hydrogen/methane selectivity," said co-corresponding author Professor Zixi Kang. "More remarkably, the membrane inherits the pressure-responsive behavior of the HOF material. The hydrogen permeance increased dramatically from 3,233 GPU at 1.2 bar to 9,842 GPU at 2.0 bar, while maintaining a high selectivity (30.01)."

This work not only presents a high-performance hydrogen separation membrane but also establishes a general hetero-nucleation engineering strategy for constructing ANC membranes with a robust "mortar-and-brick" hierarchical architecture. This approach marries the solution-processability of polymers with the ordered porosity of CPMs, paving a new way for developing advanced separation membranes for energy and environmental applications.

Other contributors include Caiyan Zhang, Haoyu Xu, Chunchen Liu, Baolei Huang, Lu Qiao, Liting Yu, Sheng Yang and Lili Fan from the Shandong Key Laboratory of Intelligent Energy Materials and the School of Materials Science and Engineering at China University of Petroleum (East China) in Qingdao, China.

This work is supported by National Key Research and Development Program of China (2024YFE0210200), National Natural Science Foundation of China (Grants No. 22171288 and 22231305), Natural Science Foundation of Shandong Province (ZR2024MB128), and Outstanding Youth Science Fund Projects of Shandong Province (ZR2022YQ15).

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.