Organic molecular sieve membranes for chemical separations

Abstract

This review proposes the concept of organic molecular sieve membranes (OMSMs) and the guiding principles for the precise structure construction and efficient process intensification of OMSMs.

Designing organic solvent separation membranes: polymers, porous structures, 2D materials, and their combinations

“…PI membranes are often prepared using the phase inversion technique to form an integrally skinned asymmetric (ISA) structure. 2,65 Polymers or precursors (i.e., poly(amic acid)) are dissolved in a mixture of solvents and cosolvents, and then exposed to a non-solvent for precipitation. The membranes are then cross-linked using diamines and conditioned with pore preserving agents, such as hexanediamine (HDA) and polyethylene glycols (PEGs), respectively.…”

“…COFs have low density, high crystallinity, large surface area, and good control over pore size and properties by fine-tuning the type of monomers, chemical reaction, and method of preparation. 2,101,[204][205][206] COFs are classified either based on the type of functionalities they contain or by the method of preparation. On the basis of functionality, COFs are classified in 6 types: (a) imine-based, 207,208 (b) boron-based, 209 (c) keto-enamine based, 72,210 (d) triazine-based, 211 (e) urea-based, 212 and (f) C-C bonded.…”

“…Organic solvents are widely used in chemical, pharmaceutical, and food industries, and they must be separated from intermediate chemicals or products for reuse to minimize waste and lower the cost. [1][2][3][4][5] Currently, organic solvent separation is achieved using phase-changing processes such as distillation, crystallization, and evaporation, which are energy-intensive and consume 10 -15% of the world's total energy. 5,6 For example, separation of p-xylene and o-xylene with similar boiling temperatures requires ~150 theoretical plates for distillation.…”

Efficient ethylene/ethane separation through ionic liquid-confined covalent organic framework membranes

“…[11][12][13] Covalent organic frameworks (COFs), with long-range ordered structures, uniform channels and easily tailored functionalities, are expected to become next generation membrane materials. [14][15][16][17] COF membranes usually possess channel sizes greater than 1 nm, which in theory could afford high ethylene permeance. Nevertheless, utilization of COF membranes for ethylene/ethane separation remains unexplored so far, most probably because the channel sizes of COF membranes are larger than both ethylene (0.42 nm) and ethane (0.44 nm) molecules and thus are unable to achieve highly selective ethylene/ethane separation based on the conventional physical sieving mechanism.…”

Photo-tailored heterocrystalline covalent organic framework membranes for organics separation

“…Moreover, the COF material features an ordered porous structure that has up to 100 times higher surface area than most network polymers 15 . Theoretically, high-crystalline COF membranes (COMs) formed totally by rigid crystallites can harvest high solute selectivity and possible high solvent permeability, however, the defect-free membranes are quite difficult to fabricate [16][17][18] . Low crystalline COMs are much easier to fabricate, but often accompany with much less ordered structure and a dramatic sacrifice in solute selectivity as well as possible solvent permeability 19,20 .…”