Engineer Nanoscale Defects into Selective Channels:MOF-Enhanced Li^(+) Separation by Porous Layered Double Hydroxide Membrane

Two-dimensional(2D)membrane-based ion separation technology has been increasingly explored to address the problem of lithium resource shortage,yet it remains a sound challenge to design 2D membranes of high selectivity and permeability for ion separation applications.Zeolitic imidazolate framework functionalized modified layered double hydroxide(ZIF-8@MLDH)composite membranes with high lithium-ion(Li^(+)) permeability and excellent operational stability were obtained in this work by in situ depositing functional ZIF-8 nanoparticles into the nanopores acting as framework defects in MLDH membranes.The defect-rich framework amplified the permeability of Li^(+),and the site-selective growth of ZIF-8 in the framework defects bettered its selectivity.Specifically speaking,the ZIF-8@MLDH membranes featured a high permeation rate of Li^(+) up to 1.73 mol m^(−2) h^(−1) and a desirable selectiv-ity of Li^(+)/Mg^(2+) up to 31.9.Simulations supported that the simultaneously enhanced selectivity and permeability of Li+are attributed to changes in the type of mass transfer channels and the difference in the dehydration capacity of hydrated metal cations when they pass through nanochannels of ZIF-8.This study will inspire the ongoing research of high-performance 2D membranes through the engineering of defects.

Building surface defects by doping with transition metal on ultrafine TiO_2 to enhance the photocatalytic H_2 production activity

Inefficient charge separation and limited light absorption are two critical issues associated with high‐efficiency photocatalytic H2production using TiO2.Surface defects within a certain concentration range in photocatalyst materials are beneficial for photocatalytic activity.In this study,surface defects(oxygen vacancies and metal cation replacement defects)were induced with a facile and effective approach by surface doping with low‐cost transition metals(Co,Ni,Cu,and Mn)on ultrafine TiO2.The obtained surface‐defective TiO2exhibited a3–4‐fold improved activity compared to that of the original ultrafine TiO2.In addition,a H2production rate of3.4μmol/h was obtained using visible light(λ>420nm)irradiation.The apparent quantum yield(AQY)at365nm reached36.9%over TiO2‐Cu,significantly more than the commercial P25TiO2.The enhancement of photocatalytic H2production activity can be attributed to improved rapid charge separation efficiency andexpanded light absorption window.This hydrothermal treatment with transition metal was proven to be a very facile and effective method for obtaining surface defects.