1Kazuya TomitaKyushu university

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Porous materialsPorous materials have many pores in the structure and the property relavant to it.

Zeolite A kind of aluminosilicates with robust structure

MOF （ Metal-Organic Framework ）　 Framework from metals and organic linkers

COF （ Covalent-organic Framework ）　 Framework which consists of covalent bonds

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HOF (Hydrogen-bonded Organic Framework)The organic framework from hydrogen bonds

Self-assembly

linkers HOFEasy synthesis because of being able to utilize hydrogen bonds

Easy reuse by recrystallization

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However, if a novel HOF with superior properties is developed,the mainstream in porous materials field might focus on HOF.

A new HOF, HOF5, was reported and it has the best adsorption property of all HOFs and it is even comparable to MOFs.

Delay of the reserch and inferior propertiesto MOF by being fragile due to hydrogen bond’s weakness

About HOF HOF’s defects

New linkerHOF

Hydrogen bond points

N

NN NH2

H2N

NN

N

H2N

NH2

NN

N

NH2

H2N

N

NNH2N

NH2

L

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Synthesis of linkerHOF’s synthesis and the crystalline structure

HOF5 HOF5-a

Changing the number of hydrogen bond from

20 to 24 per one linker

Volume shrinking by 21 %

Tetraphenylethelene skeltone

Formation of HOF5 from two types of units The structural change by Desolvation From HOF5 to HOF5-a

L

If change occurs,

N₂ adsorption isotherm is Stepwise because of the transition

HOF-5a’s BET surface area is 1100 m²/g

Reversible structural change

N2 adsorption isotherm (77 K)

HOF-5HOF-5aHOF-5HOF-5aHOF-5HOF-5a

HOF5-a changes HOR5 by being soaked inacetone in low temparature and by eliminating solvents within pores it changes HOR5-a.

The structure changes reversibly

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Powder XRD measurement

HOF-5a

HOF-5

selectivity ｜ CO₂/N₂(10:90)

Why does the HOF adsorb such lots of CO2?

Adsorption property and selectivity Adsorption isotherm (296 K)

Adsorption selectivity (296 K)

N2

CH4

CO2

C2H2

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C2H2 : Maximum value of all reported HOFs

CO2 : comparable to the best MOF

The interaction between CO2

and HOF is mainly van der Waals force, not hydrogen bond.

Molecular interaction among CO2 molecules which are guest

By Rietveld refinement, details of sites was elucidated.

Two types of sites

Exploration of CO2 adsorption sites Neutron diffraction measurement

SiteⅠ SiteⅡ

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CO2 adsorption in HOF5-a

Interaction among CO2 molecules

Quasi-one-dimensional adsorption

The interaction is van der Waals

The result of DFT calculation is consistent with Rietveld refinement

Two types of adsorption energy

SiteⅠ 　　 39.9 kJ/mol

SiteⅡ 　　 37.3 kJ/mol

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Exploration of CO2 adsorption sites

summary

HOF5-a has high CO2 adsorption capability and selectivity

The interaction between CO2 and HOF is van der Waals force

Transition from HOF-5 to HOF5-a by desolvation

CO₂ molecules’ quasi-one-dimensional adsorption

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Supporting Information

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Crystalline datas

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Crystalline datas

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Structure

HOF5 HOF5-a

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Gas adsorption property

N2

CH4

CO2

C2H2

N2

CH4

CO2

C2H2

273 K

296 K

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Gas adsorption selectivity296 K

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Comparisons with others porous materials

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HOF5 HOF5-a

Appearances of HOF5 and HOF5-a

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Calculation of BET surface area