Multidimensional Building Blocks for Molecular Sieve Membranes

Adaptive healing of stress-induced dynamic cracks in a metal-organic framework membrane using nanoparticles

Dewatering of aqueous azeotropes is crucial and pervasive in raw chemical refineries and solvent recovery in the chemical industry but is recognized as one of the most energy-intensive processes. Pervaporation using crystalline molecular sieve membranes provides an energy-efficient solution, but stress loads stemming from thermal and mechanical risks of pervaporation are most likely to cause membrane cracks, which greatly reduces reliability of membranes in real-world applications. Here, we propose adaptive healing of stress-induced dynamic cracks (AHSDC) in the membrane in a risk-responding manner before separation by using in situ-formed nanoparticles in the same chemical environment. These nanoparticles naturally filled in fissure gaps once cracks formed in the membrane, forming adaptive healing zones. Without loss of dewatering capacity, the separation durability of the membrane after AHSDC was improved by at least two orders of magnitude. The membrane also exhibited tolerance to industrial-grade azeotropes that epitomize industrial multisource nature and complexity.

Solution processing of crystalline porous material based membranes for CO2 separation

The carbon emission problem is a significant challenge in today's society, which has led to severe global climate issues. Membrane-based separation technology has gained considerable interest in CO2 separation due to its simplicity, environmental friendliness, and energy efficiency. Crystalline porous materials (CPMs), such as zeolites, metal-organic frameworks, covalent organic frameworks, hydrogen-bonded organic frameworks, and porous organic cages, hold great promise for advanced CO2 separation membranes because of their ordered and customizable pore structures. However, the preparation of defect-free and large-area crystalline porous material (CPM)-based membranes remains challenging, limiting their practical use in CO2 separation. To address this challenge, the solution-processing method, commonly employed in commercial polymer preparation, has been adapted for CPM membranes in recent years. Nanosheets, spheres, molecular cages, and even organic monomers, depending on the CPM type, are dissolved in suitable solvents and processed into continuous membranes for CO2 separation. This feature article provides an overview of the recent advancements in the solution processing of CPM membranes. It summarizes the differences among the solution-processing methods used for forming various CPM membranes, highlighting the key factors for achieving continuous membranes. The article also summarizes and discusses the CO2 separation performance of these membranes. Furthermore, it addresses the current issues and proposes future research directions in this field. Overall, this feature article aims to shed light on the development of solution-processing techniques for CPM membranes, facilitating their practical application in CO2 separation.

Energy-efficient extraction of linear alkanes from various isomers using structured metal-organic framework membrane

Extraction of low concentration linear alkanes (C5-C7) from various isomers is critical for the petrochemical industry. At present, the separation of alkane isomers is mainly accomplished by distillation, which results in substantial energy expenditure. Metal-organic frameworks (MOFs) with well-tailored nanopores have been demonstrated to be capable of realizing molecule-level separation. In this study, oriented HKUST-1 membranes are formulated according to the morphology-biased principle and finally realized with a low dose synthesis method for terminating undesired crystal nucleation and growth. The fully exposed triangular sieving pore array of the membrane induces configuration entropic diffusion to split linear alkanes from mono-branched and di-branched isomers as well as their cyclical counterparts. Typically, the current separation technique consumes 91% less energy than vacuum distillation. Furthermore, our membranes can realize one-step extraction of normal-pentane, normal-hexane and normal-heptane from a ten-component alkane isomer solution that mimics light naphtha.