Preparation And Morphology Control Of Ldhs Materials Growth On MOFs And Their Application In Photocatalysis And Electrocatalysis

The large amount of fossil fuel consumption caused by human production and living has led to a series of environmental and energy problems.It is of great practical significance to develop an effective photo/electric-catalyst to realize energy conversion or storage.Metal-organic framework materials(MOFs)are great carriers or templates because their unique material advantages,such as high porosity,large specific surface area,abundant active sites of unsaturated coordination,and functionalized pore structure,etc.,and their derived nanocomposites play an important role in different energy storage and conversion applications.Layered double hydroxides(LDHs)are ideal photo/electric catalytic materials,with highly dispersed and tunable metal cation composition and adjustable structure and chemical properties.This paper mainly focuses on the synthesis and catalytic application of MOF-derived LDHs materials and the study of their catalytic properties.The specific research contents are as follows:1.Template synthesized defect-rich NiCo-layered double hydroxide hollow nanocage for highly selective photoreduction of CO2 to CH4:The NiCo-LDH with hollow nanocage morphology(HC-NiCo-LDH)was synthesized by chemical etching the ZIF-67 template.Compared to conventional Bulk-NiCo-LDH,the HC-NiCo-LDH significantly increased the selectivity of CH4 from 8.92%to 62.66%and suppressed the H2 evolution from 44.92%to barely 1.77%,under visible light irradiation λ>400 nm.In addition,HC-NiCo-LDH has good cycling stability,CH4 selectivity is basically unchanged after 8 cycles,and the hollow morphology is maintained.X-ray absorption spectra showed that there were abundant oxygen vacancies and metal vacancy defects in HC-NiCO-LDH.Further spectroscopic characterization found that the existence of defects regulated the band gap of photocatalyst and promoted the effective separation of photogenerated electron holes,which was also confirmed by theoretical calculations.This work provides a new perspective for the design of cheap photocatalytic CO2 methanation catalysts.2.POM@MOF@LDH composite material constructed by MOF as a medium and its electrocatalytic application:A new material POM@MOF@LDH was prepared by in situ growth of LDH on polyacid MOF(POMOF).A series of control experiments were conducted,it turned out that the uniform growth of CuCu-LDH on the surface of POMOF could be achieved by controlling the feed ratio of added salt to POMOF.By exploring the growth mechanism,it was found that the coordination of Cu in CuCo-LDH and unsaturated coordinated COO-in POMOF was the main connection in the process of in-situ growth of LDH.And the structure integrity of POMOF would not be affected maintain,even and the POM in POMOF was replaced.When the material is applied to electrocatalytic water splitting,it can be seen that the performance of POMOF@LDH achieves the effect of" a whole greater than the sum of the parts".This method provides a feasible scheme for the design of POM-MOF-LDH ternary composites.