Metal-organic frameworks (MOFs) and polymer composites are attracting attention for their versatility. However, during the compounding process, the pores of MOFs are susceptible to the penetration of small molecules such as monomers or curing agents, as well as the interpenetration of polymers, resulting in a decrease in the porosity of MOFs, which limits the performance of MOFs in polymers. In view of this, Professor Zhao Jianqing of South China University of Technology and Associate Professor Xie Weiqi of Central South University proposed the concept of molecular cage metal-organic framework (MC-MOF). The conjugated ligand is used to shrink the MOF window, which can effectively hinder the penetration of small molecules or polymers without sacrificing porosity, thereby protecting the pore structure of MC-MOF and optimizing the performance of MOF/polymer composites.
The authors rationally designed the MC-MOF from the aspects of side group selection, color and cost, and further revealed the effectiveness and universality of the molecular cage effect by combining experiments and simulations. The molecular cage acts as a barrier to molecular permeation, allowing MC-MOF to maintain high porosity in the polymer, enabling functions such as light capture and thermal regulation. Polymer matrix composites containing 0.5 wt% MC-MOF exhibit ultra-high haze (93%, 550 nm) while maintaining high light transmittance, enabling efficient forward scattering. The introduction of MOFs also imparts a broad UV shielding and photoluminescence response to the material, and enhances the mechanical properties of the polymer. The material is used in the field of energy-efficient building design, which effectively diffuses sunlight, reduces uncomfortable glare, and increases natural lighting. MC-MOF/polymer has the potential to reduce energy consumption in buildings due to its lower thermal conductivity compared to glass, which slows heat transfer and reduces direct sunlight. The design principle of constructing molecular cages through ligand engineering provides an effective solution for MOFs to maintain high porosity in polymers, and opens up new prospects for their application in the field of energy management. The relevant results were published in Science Advances, a top international comprehensive journal, and were selected as the first page headline to be reported on the official website of Science Advances.
Summary: In this study, a molecular cage-like metal-organic framework (MC-MOF) was developed to hinder the molecular penetration of MOFs in polymers. MC-MOF has shown great potential in enhancing the energy management of polymers, demonstrating excellent light capture and thermal regulation. It helps to achieve uniform lighting distribution in sustainable building design and reduces energy consumption compared to traditional glass materials. The concept of designing MC-MOFs with high porosity and custom windows through ligand engineering provides a versatile approach to optimize the performance of MOFs in polymer matrices, and also opens up more possibilities for the application of MOFs/polymer composites in sustainable energy. Source: Frontiers of Polymer Science