These-projetCMellot

Nicholas Harris Nicolas

Description

A PhD Studentship available early 2006 at the Royal Institution/University College of London Molecular Simulation of CO Gas Adsorption in Hybrid Metal-Organic Materials 2 An EU-funded PhD studentship is available in the Davy Faraday Research Laboratory of the Royal Institution to work on molecular simulations of CO 2 adsorption in novel nanoporous metal-organic framework materials. Metal-organic frameworks (MOFs) form a recently developed class of porous materials with open architectures built from metal ions linked together by organic bridging ligands. The project will involve the use of a wide range of computational tools, including forcefield-based Monte Carlo modelling techniques and quantum chemical methods, to elucidate the atomic-scale mechanisms of gas adsorption in such materials. Attention will be especially focussed on flexible materials which possess the ability to expand and contract their pore volume during the adsorption process. The project forms part of a larger EU-funded STREP programme and the work will be carried out in close collaboration with experimental groups specializing in adsorption measurements and crystallography, both located in France. Further scientific details of the host Institution and the project are available at /www.ri.ac.uk/DFRL/ and /www.ri.ac.uk/DFRL/postgrad_pages/abstract.htm respectively. The studentship will be based at the Royal Institution in London under the supervision of Dr Robert Bell ...

Informations

• Publié par: Pheav
• Nombre de lectures: 18
• Langue: English

Extrait

A PhD Studentship available early 2006 at the

Royal Institution/University College of London

Molecular Simulation of CO

2

Gas Adsorption in Hybrid Metal-Organic Materials

An EU-funded PhD studentship is available in the Davy Faraday Research Laboratory of the Royal

Institution to work on molecular simulations of CO 2 adsorption in novel nanoporous metal-organic

framework materials.

Metal-organic frameworks (MOFs) form a recently developed class of porous materials with open

architectures built from metal ions linked together by organic bridging ligands. The project will involve

the use of a wide range of computational tools, including forcefield-based Monte Carlo modelling

techniques and quantum chemical methods, to elucidate the atomic-scale mechanisms of gas

adsorption in such materials. Attention will be especially focussed on flexible materials which possess

the ability to expand and contract their pore volume during the adsorption process.

The project forms part of a larger EU-funded STREP programme and the work will be carried out in

close collaboration with experimental groups specializing in adsorption measurements and

crystallography, both located in France.

Further scientific details of the host Institution and the project are available at

/www.ri.ac.uk/DFRL/

and

/www.ri.ac.uk/DFRL/postgrad_pages/abstract.htm

respectively.

The studentship will be based at the Royal Institution in London under the supervision of Dr Robert

Bell (Fellow at the RI) and Dr. Caroline Mellot-Draznieks (Chargée de Recherche au CNRS), with the

student registered for the degree of PhD at University College London.

Applications are sought from EU students with a good Master's degree (2:1 MSci or equivalent) in

Chemistry or Physics. The studentship provides full university fees for UK and EU residents and a tax-

free stipend of £14,000 per annum.

The studentship is due to start as soon as possible in 2006

and will be for 3 years.

Applications, including a covering letter and full CV with the names of at least 2 referees, should be

sent to

Dr. Caroline Mellot-Draznieks, Royal Institution, 21 Albemarle Street, London W1S

4BS, UK. Email:

[e-mail]

.

Tel: [phone].

ABSTRACT

Carbon dioxide is the most important greehouse gas implicated in global warming, and enormous effort

is being put into finding new methods of separating, capturing and/or storing CO

2

, which are both

economical and environment friendly. Hybrid materials are interesting alternatives to other media such

as zeolites, due to their low framework density, excellent thermal stability and inexpensive synthesis.

Some of the key aspects governing the performance of such materials for CO

2

adsorption are (i) the

chemical nature of the organic ligands, especially grafted ligands, which can affect selectivity towards

CO

2

adsorption, (ii) the pore structure and (iii) the framework flexibility, all of which influence adsorption

capacity.

Metal-organic frameworks (MOFs) form a new

class of hybrid materials with open architectures

built from metal ions linked together by organic

bridging ligands, commonly carboxylate ions.

Recently, new types of MOFs have been

discovered that possess flexible frameworks,

able to expand and contract their pore volume,

depending on the nature and polarity of the

guest molecules (See Figure). Typically, some

metal carboxylates exhibit very unusual swelling

behaviour upon adsorption-desorption. Unlike

zeolitic materials that are characterized by a

relatively rigid framework under adsorption

conditions, such flexible frameworks may offer

the unique advantage of performing the

adsorption of guest molecules in a more specific

fashion by simply adapting their framework

structure accordingly.

Flexible

framework

of

MIL-88,

a

chromium

carboxylate, upon dehydration/adsorption process.

The

current

project

tackles

the

simulation

of

the

adsorption

of

CO

2

in

flexible

hybrid

frameworks

using

Monte

Carlo

based

techniques

in

the

grand

canonical

(P,V,T)

and

canonical

(N,V,T)

ensembles

together

with

forcefield

based

ener

gy

minimization

techniques.

The

work

aims

at

simulating

isotherms

and

isosteric

heats

of

adsorption

as

a

function

of

loading,

while

taking

into

account

the

dynamical

response

of

the

framewor

k

to

the

adsorption

of

CO

2

.

Unlike

similar

rigid

metal-organic

frameworks,

proper

modelling

of

the

flexibility

of

the

hybrid

framework

during

the

simulated

adsorption

process

is

an

essential

and

new

facet

of

the

present

proposed

work.

Indeed,

a

crucial

part

of

the

work

relates

to

the

correct

description

of

coulombic

interactions

and

the

use

of

appropriate

forcefield

for

desc

ribing

the

flexibili

ty

of

the

framework.

None

existing

methods

are

available

in

this

field,

and

it

will

be

a

c

ritical

challenge for simulating these systems accurately.

We

expect

the

simulation

wor

k

to

allow

us

to

understand

the

very

unusual

shapes

of

CO

2

isotherms

(hysteresis,

steps,

maximum

capaci

ty,

curvature)

and

the

evolution

of

CO

2

adsorption

enthalpies

as

a

function

of

loading.

In

order

to

ensure

the

significance

of

our

simulations,

we

expect

important

interactions with

the

simulation group

in

Montpellier and

experimental partne

rs,

typical

ly

thermodynamic

measurements in Ma

rseilles, and

synchrotron data from Versailles/ESRF.

Another

challenging

aspect

of

the

project

relates

to

the

simulation

of

CO

2

in

ve

ry

large

pore

mate

rials,

such

as

the

ve

ry

recent

MIL-100

and

MIL-101

hybrids.

1,2

These

materials

possess

a

rigid

a

rchitecture

that

is

reminiscent

of

the

MTN

zeolite

topology

and

exhibit

a

hierarc

hy

of

micro-

(Ø

≈

6.5-8.5

Å)

and

mesopo

res

(Ø

≈

25-30

Å)

with

ve

ry

large

surface

areas

(3000-5000

m

2

.g

-1

).

Indeed

the

simulation

of

CO

2

adsorption will aim at interpreting the adsorption capacities of these unusual materials.

References

1.

C. Mellot-

Draznieks et

al.

Angew. Chem. Int. Ed.

2004

, 43

(46) 6296-6301.

2.

C. Mellot-

Draznieks et

al.

Science

2005

, 309 , 2040-2042.

3.

G. Maurin, P. Llewellyn & R.G. Bell,

J. Phys. Chem. B

,

2005

, 109, 16084.