para‐Xylene Ultra‐selective Zeolite MFI Membranes Fabricated from Nanosheet Monolayers at the Air–Water Interface

Abstract

The control of membrane morphology and microstructure is crucial to improve the separation performance of molecular-sieve membranes. This can be enabled by making thin, dense, and uniform seed-crystal coatings, which are then intergrown into continuous membranes. Herein, we show a novel and simple floating particle coating method can give closely packed monolayers of zeolite nanosheets on nonporous or porous supports. The zeolite nanosheet monolayer is formed at the air-water interface in a conical Teflon trough. As the water in the trough is drained, the monolayer is deposited on a support placed below. Membranes prepared by gel-free secondary growth of the nanosheets deposited by this method show unprecedented ultra-selective performance for separation of para- from ortho-xylene (separation factor >10 000).

Separation of Aromatics/Cyclic Aliphatics by Nonporous Adaptive Pillararene Crystals

“…[6,7] In this case,t he selectivity of Ben speculated from the sorption isotherms of EtP6b did not meet the experimental results.T he structural similarities of 2(CH)@EtP6 and 2-(Ben)@EtP6 lead to no selectivity while the differences of 2(MCH)@EtP6 and Tol@EtP6 result in MCH selectivity.This separation mechanism based on final guest-loaded crystal structures was further confirmed by Tol/Ben and Tol/CH adsorption experiments (Supporting Information,. This is quite different from robust MOFs,w here the selectivity of one gas/vapor over another can be easily recognized from sorption isotherms.…”

“…[6] Thed ifficulties in finding suitable materials lie in the similar molecular sizes of cyclic aliphatics and aromatics (Scheme 1a). [6] Thed ifficulties in finding suitable materials lie in the similar molecular sizes of cyclic aliphatics and aromatics (Scheme 1a).…”

“…Pillar[n]arenes have emerged as an ew generation of supramolecular macrocyclic hosts in last decade. Chemical structures:a )benzene (Ben), toluene (Tol), cyclohexane (CH), and methylcyclohexane (MCH);b )perethylated pillar-[5]arene (EtP5) and pillar [6]arene (EtP6). [8,9] Recently,o ur group have pioneered the research of pillar[n]arene-based nonporous adaptive crystals.…”

“…An alternative energy-efficient separation strategy is to exploit the molecular, chemical, and geometrical differences of aromatics and cycloalkanes in adsorptive separation using ordered nanoporous materials. [6] Thed ifficulties in finding suitable materials lie in the similar molecular sizes of cyclic aliphatics and aromatics (Scheme 1a). Although adsorptive separation of aromatics and cyclic aliphatics has been achieved using metal-organic frameworks (MOFs), [7] such materials have some deficiencies which cannot be ignored in practical conditions.F or example,m ost MOFs that can separate aromatics and cyclic aliphatics exhibit ap reference for aromatics owing to the p-p interactions between the phenyl rings of guests and the framework.…”

Continuous Zeolite MFI Membranes Fabricated from 2D MFI Nanosheets on Ceramic Hollow Fibers

“…In recent works, [4,5] it has been shown that the void spaces can be effectively closed by growth of MFI domains,d riven by supply of silicate reactants from an underlying Stçber silica-derived disk support. In recent works, [4,5] it has been shown that the void spaces can be effectively closed by growth of MFI domains,d riven by supply of silicate reactants from an underlying Stçber silica-derived disk support.…”