WO2009127896A1

WO2009127896A1 - Synthesis of an ordered covalent monolayer network onto a surface

Info

Publication number: WO2009127896A1
Application number: PCT/IB2008/002342
Authority: WO
Inventors: Nikolas Zwaneveld; Rémy PAWLAK; Louis Porte; Daniel Catalin; Denis Bertin; Mathieu Abel; Didier Gigmes
Original assignee: Universite D'aix-Marseille I
Priority date: 2008-04-18
Filing date: 2008-04-18
Publication date: 2009-10-22

Abstract

The invention relates to a process for synthesizing a covalent ordered network onto a surface, comprising depositing onto said surface a polyfunctional boronic acid or a boronate ester, and reacting the polyfunctional boronic acid or boronate ester with a second reactant so as to obtain a bo roxine-l inked or a boronate-linked organic monolayer network. The invention also relates to a covalent ordered monolayer on a surface, comprising a boroxine-linked or a boronate-linked network and has a two dimensional nano-meter scale porous structure. The boroxine-linked or boronate-linked network may have a predominance of structured pores.

Description

SYNTHESIS OF AN ORDERED COVALENT MONOLAYER NETWORK

ONTO A SURFACE

TECHNICAL FIELD

The present invention relates to the field of synthesizing covalent two- dimensional monolayer networks on a surface using at least one reactant.

BACKGROUND INFORMATION

The production of self-organized two-dimensional molecular networks offers some of the best possibilities to pattern and produce semi-conducting architectures beyond what is currently possible with lithography. The ability to produce well-ordered networks in the nanometer or angstrom ranges in an efficient and reproducible manner is greatly desired for computing applications because of wavelength effects in the photolithographic process below -50 nanometers. Generally speaking, the synthesis of monolayer ordered networks is of interest in the fields of nano-electronics, quantum computing, biological sensing, and nanotechnology fields. Additionally there is general interest in the modification of electronic properties, physical properties, and chemical properties of surfaces using such organized two- dimensional molecular networks.

Monolayer ordered networks have already been realized using hydrogen bonded systems (for example see Wan, L. J- Ace. Chem. Res 2006, 39, 334), metal-organic systems (James, S. L. Chemical Society Reviews 2003, 32, 5, 276) and metal-ligand coordination systems (for example De Feyter, S., De Schryver, C, Chem. Soc. Rev., 2003, 32, 139). However, they are limited in their application by the weak nature of the hydrogen and coordination bonding that is used to make these networks. Thus covalently bonded networks offer greater flexibility for further application in for example the patterning of devices or the modification of surface properties. The production of highly-ordered, porous, layered, three-dimensional structures formed from self-assembly in weak solvents (WO 2007/098263 Lavigne et al. and US 2006/0154807 A1 Yaghi et al.) has previously been demonstrated for gas-adsorption and storage applications. These so termed Covalent Organic Frameworks or COFs are used to produce powders displaying a porous covalent structure.

The present invention aims to discover a process of formation of a surface covalent network on a surface, to achieve complete monolayer coverage with the required stability for further usage and synthesis.

BRIEF SUMMARY

The present invention is based on the formation of a novel two- dimensional ordered covalent porous network across a surface, and comprising an organized boroxine- or boronate- linked organic structure that can be formed from the deposition of boronic acids or esters thereof, alone or combined with complementary reactants. In addition, it has been discovered and demonstrated that the size and structure of the thus obtained network can be controlled by judicious selection of the components.

More particularly, one embodiment of the invention relates to a process for synthesizing a covalent ordered network onto a surface, comprising: depositing onto said surface a polyfunctional boronic acid or a boronate ester, and reacting the polyfunctional boronic acid or boronate ester with a second reactant so as to obtain a boroxine-linked or a boronate- linked organic monolayer network.

In one embodiment, the process comprises reacting the polyfunctional boronic acid with itself as second reactant.

In one embodiment, the process comprises reacting the polyfunctional boronic acid with another polyfunctional boronic acid.

In one embodiment, the process comprises reacting the polyfunctional boronic acid with a second reactant selected from the group consisting of polyfunctional diol, polyfunctional diamine, polyfunctional amino alcohol, polyfunctional thiol. In one embodiment, the process comprises reacting a boronate ester with a second reactant selected from the group consisting of polyfunctional diol, polyfunctional diamine, polyfunctional amino alcohol, polyfunctional thiol.

In one embodiment, the process comprises depositing the second reactant onto said surface prior to the polyfunctional boronic acid so as to prevent the polyfunctional boronic acid from reacting with itself.

In one embodiment, the process comprises co-depositing the polyfunctional boronic acid or boronate ester and the second reactant at the same time onto said surface.

In one embodiment, the process comprises depositing the polyfunctional boronic acid or the boronate ester and the second reactant under ultra high vacuum and by sublimation of the reactants.

In one embodiment, the process comprises adding functional substituents to the reactants prior to deposition onto said surface.

In one embodiment, the process comprises a further step of incorporating heterocyclic macrocycles into the network.

In one embodiment, the process comprises a further step of selectively depositing a material in pores of the porous covalent organic network.

In one embodiment, the reactants are deposited onto an orientated crystalline surface.

One embodiment of the invention also relates to a process of manufacturing a network of nanoparticles onto a surface, comprising: synthesizing a porous covalent organic network onto the surface according to the above-described process, and selectively depositing a material in pores of the porous covalent organic network.

In one embodiment, the process comprises a further step of removing the network.

One embodiment of the invention also relates to a covalent ordered monolayer on a surface, comprising a boroxine-linked or a boronate-linked network and having a two dimensional nano-meter scale porous structure.

In one embodiment, the boroxine-linked or a boronate-linked network comprises a predominance of pores having a hexagonal structure. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other features will be described in greater detail in the following description of one or more embodiments, given in relation with, but not limited to the following figures:

- Fig. 1 shows an example of a covalent ordered organic network formed from 1 ,4-benzenediboronic acid, resulting in a boroxine-linked network;

- Fig. 2 shows an example of a covalent ordered organic network formed from a 1 ,3,5-benzenetriboronic acid, resulting in a boroxine-linked network;

- Fig. 3 shows an example of a covalent ordered organic network formed from 2,3,6,7, 10,11-hexahydroxytriphenylene and 1 ,4- benzenediboronic acid, resulting in a boronic ester linked network;

- Fig. 4 shows an example of a covalent ordered organic network formed from a reaction of boronic acid and functionalized reactants, resulting in a boronic ester-linked network;

- Fig. 5 shows an example of a covalent ordered organic network formed from the reaction of a heterocyclic boronic ester of 1 ,4- benzenediboronic acid and 2,3,6,7,10,11-hexahydroxytriphenylene, resulting in a boronic ester linked network;

- Fig. 6a shows a measured profile and pore size of a covalent ordered organic network formed from 1 ,4-benzenediboronic acid on Ag(111 );

- Fig. 6b shows a measured vertical height of a covalent ordered organic network formed from 1 ,4-benzenediboronic acid on Ag(111 );

- Fig. 7 shows a DFT modeled structure of a covalent ordered organic network formed from 1 ,4-benzenediboronic acid;

- Fig. 8a shows a measured profile and pore size of a covalent ordered organic network formed from 1 ,4-benzenediboronic acid and 2,3,6,7,10,11-hexahydroxytriphenylene on Ag(111 );

- Fig. 8b shows a measured vertical height of a covalent ordered organic network formed from 1 ,4-benzenediboronic acid and 2,3,6,7,10,11- hexahydroxytriphenylene on Ag(111 ); and - Fig. 9 shows a DFT modeled structure of a covalent ordered organic network formed from 1 ,4-benzenediboronic acid and 2,3,6,7,10,11- hexahydroxytriphenylene.

DETAILED DESCRIPTION

In the following description, numerous specific details are given to provide a thorough understanding of embodiments. The embodiments can be practiced without one or more of the specific details, or with other methods, equipments, materials, etc. In other instances, well-known materials or operations are not shown or described in detail to avoid obscuring aspects of the embodiments. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The present inventors have discovered that a covalently linked, ordered monolayer network on a surface can be formed from the deposition and reaction of boronic acids with themselves or with a polyfunctional secondary reactant or by the reaction of boronic esters with a polyfunctional second reactant. The resulting network is covalently bonded, thus providing remarkable stability and enhanced functionality. The characteristics and properties of the resulting network may be varied and altered by changing the reactants and by incorporating functional groups into the reactants.

Advantageously, the ordered monolayer network is covalently bonded and thus stable under standard atmospheric conditions. Additionally the network can by readily hydrolyzed in a humid atmosphere providing a ready method for removing the network after its utilization if this is desired. Embodiments of a process for producing such a covalent ordered organic network will be described hereinafter in further detail.

First embodiment: formation of a monolayer network from the reaction of a boronic acid with itself

In one embodiment of the present invention, a boroxine-linked network is produced using an anhydride formation process. A boronic acid such as 1 ,4-benzenediboronic acid or BDBA is reacted with itself and generates a self-assembled, ordered, stable, monolayer network as shown in Fig. 1 and as described below:

1 ,4-benzenediboronic acid

This process occurs without the need for additional catalysts or reactants, and an anhydride network is formed having a relatively small pore size. Example of formation process:

The BDBA is purified then loaded into a sublimation equipment, which in this example is a UHV (Ultra High Vacuum) sublimation equipment, and is deposited onto a flat surface, for instance a mono-crystalline surface (gold, silver, nickel, graphite etc.).

For example, an orientated crystalline Ag surface is prepared by repeated cycles of argon sputtering (800V, 1 μA) and annealing at 700 K. The BDBA is purified by careful vacuum sublimation at 445K and approximately 10 Pascal. The BDBA is then loaded into the sublimation equipment, for instance PVD equipment (Physical Vapor Deposition). The BDBA is then out-gassed in vacuum and evaporated from a heated molybdenum crucible evaporator under ultra-high vacuum conditions (1x10⁷ Pascal) onto the Ag surface. The deposition rate is about 0.5 monolayer per minute (one monolayer corresponding to a complete layer of the dense molecular phase).

The BDBA evaporator temperature may be varied between 370 and 460 K. During the deposition the sample can be kept either at room temperature (298K) or at 470 K. At both temperatures the structural arrangements are very similar and produce a covalently bonded network. However, higher substrate temperatures produce a clearer structure due to the improved removal of impurities and/or water molecules that are produced during the polymerization.

The resulting network can be observed using a Scanning Tunneling Microscope or STM. The organized structure is visually analyzed and found to be an ordered hexagonal structure of a 15.3 A pore size as can be seen in Fig. 6a and Fig. 6b. This pore size corresponds closely to the pore size in the model from density functional theory (DFT) calculation of 15.25 A, as can be seen in Fig 7. In other embodiments, the conditions for forming the network under UHV may depend on the reactants and the reactions that take place, but may be varied according to a sublimation temperature between ambient (-298K) and 500K, a pressure of approximately 1x10⁷ - IxIO^"8 Pascal, and a substrate temperature between 77K and 570K. However, these temperatures in no way restrict the range of reaction conditions and are provided here as a guide to the temperature and pressure ranges used.

The UHV applied to the samples after sublimation, evaporates and evacuates the water generated during reaction; however the removal of this water can be accelerated by heating of the substrate either during the deposition or by post-deposition annealing. The covalent nature of the network and the formed structural arrangements were found to be effectively independent of both the evaporator and substrate temperatures. However, it should be noted that higher substrate temperatures produce a clearer network due to the removal of some impurities and/or water molecules that are produced during the polymerization.

The extent of surface coverage can be varied between <0.01 monolayer to >1 monolayer by control of the sublimation temperature and the sublimation time. The formation process is self-limiting, so that the formation of a single monolayer is favored.

Throughout the coverage range the formed networks show the same level of order and pore size, which indicates that there is not a surface area coverage effect on the network formation. Image analysis techniques show that the majority of the pores are of a hexagonal structure, with secondary maxima corresponding to pentagon, heptagon, and octagon structures. The hexagon structure is the most stable and lowest energy system and thus is, as expected, the dominant geometry in the network. With careful observation, it can be seen that the different polygon structures are caused either by deformation of the perfect hexagon structure or by incomplete ring closure in the boroxine. As indicated above, the network can be annealed after deposition at elevated temperatures (for example 475K) to eliminate impurities and the water produced during the network formation. This annealing step may additionally help to complete any unfinished chemical reactions on the surface. However, it is to be noted that annealing seems ineffective with a covalent ordered organic network to remove defects, contrary to supramolecular networks, since the permanence of the covalent bond structures do not allow rearrangement.

In other respects, the network comprising boroxine linkages is reversible in the presence of water under atmospheric conditions because the water molecules hydrolyze the chemical bonds. The reaction and chemical bonds are permanent under conditions that are dry, UHV₁ and/or high temperature.

The thermal stability of the network was observed to confirm the covalent bonding of molecules. It was found that the materials are stable up to at least 725K for short periods of time (such as up to five minutes). This confirms the covalent nature of the network as weaker bonding structures are expected to degrade at lower temperatures. For longer periods of time (such as up to 15 hours) of heating, the structure remains intact at 625K but some degradation of the order in the network was noted for those at 725K.

Other bi-functional boronic acids may also be reacted with themselves to obtain a boroxine ordered network. Triboronic acids, tetraboronic acids, etc. may also be reacted with themselves to obtain a boroxine ordered network. Some examples of such other n-boronic acids (wherein "n" can be "di", "tri", "tetra", etc.) that may be reacted with themselves are described below:

i) Other bi-functional boronic acids:

N) Other example: trifunctional boronic acids

Fig. 2 shows an example of a covalent ordered organic network formed from the above-described trifunctional phenyltriboronic acid, by reacting the acid with itself.

iii) Other example: tetra-functional boronic acids

This range of reactants is shown to only present examples and in no way restricts the range of boronic acids that may be used. More specifically embodiments of the invention may use various substituted and functionalized versions of these reactants.

Second embodiment: formation of a monolayer network using two different reactants

i) Reaction of a polyfunctional boronic acid with a second reactant

A covalently linked, ordered monolayer network can also be formed by reacting a polyfunctional boronic acid with a second reactant. The second reactant may comprise a polyfunctional diol forming a network linked through a dioxaborole. In an alternative embodiment, the second reactant may comprise a polyfunctional diamine for producing a porous network linked through diazaboroles. In still another embodiment, the second reactant may comprise of a polyfunctional amino alcohol to produce a network linked through oxazaboroles. In another embodiment, the second reactant may comprise of a polyfunctional thiol to produce a dithioborolane. In still another embodiment, the second reactant may be a different polyfunctional boronic acid producing a network constructed using boroxine linkages (boronanhydrides). For instance, an "n1 -boronic" acid may be reacted with an "n2-boronic" acid, with "n1" different from "n2" and wherein "n" can be "di", "tri", "tetra", etc.

The characteristics and properties of the resulting network may thereby be varied and altered by changing the reactants and by incorporating functional groups into the reactants. This allows for customization of the physical properties of the pores and/or the chemical properties of the monolayer.

Another advantage is that the covalent bonding interaction is also somewhat reversible between the boronic acids and the second reactant. Given the covalent, yet reversible, nature of the linkage, these assemblies form in a highly-ordered manner whereas previous efforts to form covalently- bonded networks such as this have been limited by the non-reversible nature of their bonds.

Example:

A boronate-linked network is produced by a condensation reaction wherein BDBA (1 ,4-benzenediboronic acid) as first reactant is reacted with 2,3,6,7,10,11-hexahydroxytetrephenylene or HHTP (a polyfunctional alcohol) as second reactant, to obtain, as described below and also shown in Fig. 3, a self-assembled, ordered, stable, monolayer network:

1 ,4-benzenediboronic acid

2,3,6,7,10,11-hexa (BDBA) hydroxytriphenylene

(HHTP)

Such a network is based on an esterification reaction between the boronic acid and the diol groups in the HHTP, to form boronate ester linkages.

Example of formation process: The molecular network is for instance formed by the sublimation of BDBA and HHTP under UHV onto a flat surface, for instance a clean Ag (111 ) substrate using the methods described above, i.e. by sublimation under UHV.

Preferably, the second reactant is deposited onto the surface in excess prior to the first reactant in order to prevent the BDBA from reacting with itself and therefore to inhibit the formation of the boroxine-linked network described above. For instance, the BDBA is firstly purified by careful vacuum sublimation at 445K and 10 Pascal. The BDBA and HHTP are then loaded into the sublimation equipment, and then out-gassed in vacuum and then evaporated from separate heated molybdenum crucible evaporators under ultra-high vacuum conditions (1x10⁷ Pascal) onto the clean Ag surface. The deposition rate is approximately 0.5 monolayer per minute (where one monolayer corresponds to the amount of material required to completely cover the surface with a single molecular layer of material).

HHTP molecules are then sublimed at an evaporation temperature of 500K. The BDBA evaporator temperature can be varied between 370 and 460 K. In order to ensure an excess of HHTP, an entire monolayer is first deposited on the Ag(111 ) substrate at a sublimation temperature of 500 K and a substrate temperature of 298K, then both molecules are co- evaporated onto the sample at 400K. In these conditions, the bi-molecular reaction of the boronate-linked network is preferred to the reaction of the boroxine-linked network. Finally, the substrate is annealed at about 520K to remove excess HHTP molecules and water molecules produced during reaction.

The network obtained shows an average pore size of 29.9 A, as can be seen in Fig. 8a and Fig. 8b. Such a pore size can be calculated from the analysis of STM images. This coincides well with the 29.8 A pore size derived from the calculation of a DFT model, as can be seen in Fig 9. The network is dominated by hexagonal structures, which is the most energetically favorable structure. The thermal stability of the network was observed to confirm the covalent bonding of molecules. It was found that the materials are stable up to at least 725K for short periods of time (such as up to five minutes). This confirms the covalent nature of the network as weaker bonding structures are expected to degrade at lower temperatures. For longer periods of time (such as up to 15 hours) of heating, the structure remains intact at 625K but some degradation of the order in the network was noted for those at 725K.

Other embodiments may use different second reactants (polyfunctional diol, amino alcohol, thiols, diamine...) for instance the following reactants:

With R = OH, NH₂ or SH for example. ii) Reaction of a boronate ester with a second reactant

In an alternative embodiment, the first reactant may comprise a boronate ester instead of a polyfunctional boronic acid. The boronate ester may be reacted with a second reactant such as a polyfunctional diol, a polyfunctional diamine, a polyfunctional amino alcohol, or a polyfunctional thiol in an exchange type reaction to from a more stable dioxaborole, diazaborole, oxazaboroles or dithioborolane.

Such an embodiment may be useful because boronic esters behave like the acids whilst they do not form boroxines (they do not react with themselves) and they may be more volatile and thus easier to sublime.

For instance, the formation of a bimolecular boronate network is achieved by the reaction of an alkyl boronic ester with a polyfunctional aromatic alcohol. The formation reaction in this case is driven by a transesterification reaction between a boronic ester with a polyfunctional alcohol that forms a more stable boronic ester. This could be a reaction of for example an alkyl diester of 1 ,4-benzenediboronic acid reacting with for example 2,3,6,7,10,11-hexahydroxy-triphenylene to form the same network as shown in Fig. 1.

The formation of boronic esters is firstly achieved by the heating of a boronic acid with an alkyl alcohol or an alkyl diol under simple lab conditions. One of these esters is then deposited with an aryl polyfunctional alcohol. An exchange reaction takes place, which displaces the alkyl diol or alkyl alcohols and replaces it with the aromatic polyfunctional alcohol as described below:

Where R is an alkyl or aryl group

As a specific example, a boronate-linked network can then be formed as can be seen in Fig. 5.

Thermal stability of boroxine- and boronate- linked networks

The boroxine- and boronate- linked networks that have been disclosed above display thermal stability until at least 725K at which point some degradation and delamination of the network is noted. This degradation temperature was confirmed by Thermogravimetric Analysis or TGA.

Compared with other organic polymeric networks, these networks offer significantly improved order and ease of reaction. Furthermore, compared with non-covalent systems, they offer significantly improved stability in relation to thermal stability and atmospheric pressures, as well as resistance during further reaction.

In addition, the reactants can be varied to adjust the pore-size, functionality, properties and characteristics in the desired final product, yet the acid/ester equilibrium and anhydride bonds retain reversible characteristics of a self-assembling system including self-repair and efficient formation. Other combinations of reactants

It will be understood by those skilled in the art that the above disclosed process for synthesizing an ordered monolayer porous covalently- linked organic network is susceptible of various other embodiments. In some embodiments, the reactants can be initially deposited and then the network formation is driven by application of a reduced pressure, in the range of 10³ to 10^"6 Pascal, and/or an elevated temperature in the range of 375-775K. However, any drying conditions will cause the network to form, including dry atmosphere and dry solvents. The speed of the reaction will depend upon the conditions.

Further functionality may also be added to the pores by adding functional substituents to the first or second reactant prior to formation into a network. Functionalized reactants may then be reacted with a boronic acid or boronic ester as described in the earlier embodiments. For example, it is possible to add a functionality to the 3, 6 position of 1 , 2, 4, 5-tetrahydroxy benzene, as can be seen below. The functionality may comprise, for instance, of alkyl, trimethyl silyl (TMS) or carbonic acid functionalities.

Example reaction mechanism and substituted reactant (Y=alkyl, TMS, COOH, etc.):

In the example shown in Fig. 4, this functionalized reactant is reacted with boronic acid to form a boronic ester linked network. As indicated above, the characteristics and properties (such as the pore-size, functionality, properties, and characteristics) of the resulting network may be varied and altered in a predictable manner by adjusting the reactants and by incorporating functional groups into the reactants before formation. Thus, the networks can be tailored -i.e. customized- to fit specific requirements and desired properties, for example by using the complexing ability of amines on the size of the pores.

In another embodiment, functionality may also be incorporated by including heterocyclic macrocycles, such as phthalocyanines or porphyrins, into the structure either by using a diol or diamine functionalized macrocycle or a boronic acid macrocycle.

Example reactants based on phthalocyanine and porphyrin, where M can be a metal atom such as H, Cu, Co, Fe, etc.:

While sublimation techniques have been described above, covalently linked, ordered monolayer networks may also be formed from boronate- or boroxine-based systems on a molecularly flat surface by various methods other than sublimation. Such methods of formation may include physisorption of reactants from solution, precipitation polymerization, spin coating, or any combination of these techniques. Applications

An ordered monolayer porous covalently-linked organic network made according to one embodiment of the invention is susceptible of various applications.

For instance, in one application, the network is used as a mask to deposit an ordered array of metal particles such as cobalt, iron, platinum and zinc or metallic alloys or other functional materials such as Fullerene molecules for nano-electronics applications.

Alternatively, the capability of the network to trap molecules can be shown by the deposition of a material (such as cobalt or Fullerene molecules) into the pores of the network for devices such as nano-scale hard drives or Random Access Memory (RAM).

Additionally, bio molecules or bio-receptors may be placed in the pores to produce nano-biological networks.

Additionally, the network has application in the modification of the electronic, chemical and physical properties of surfaces using such organized two-dimensional molecular networks.

Various applications are of interest in developing new generations of nano- and quantum computing devices, nano-catalytic systems, nanoreactors, biological networks, surface bound catalyst systems, or investigations into organic conduction.

If desired, the network can be readily hydrolyzed in a humid atmosphere in order to remove the network after its utilization if required. Other conventional removal methods may be used by those skilled in the art, as chemical etching, plasma etching, etc.

The various embodiments described above can be combined to provide further embodiments. All of the patents, patent applications publications and non-patent publications referred to in this specification and/or listed below are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.

Claims

1. A process for synthesizing a covalent ordered network onto a surface, comprising:

- depositing onto said surface a polyfunctional boronic acid or a boronate ester,

- reacting the polyfunctional boronic acid or boronate ester with a second reactant so as to obtain a boroxine-linked or a boronate-linked organic monolayer network.

2. A process according to claim 1 , comprising:

- reacting the polyfunctional boronic acid with itself as second reactant.

3. A process according to claim 1 , comprising:

- reacting the polyfunctional boronic acid with another polyfunctional boronic acid.

4. A process according to claim 1 , comprising:

- reacting the polyfunctional boronic acid with a second reactant selected from the group consisting of polyfunctional diol, polyfunctional diamine, polyfunctional amino alcohol, polyfunctional thiol.

5. A process according to claim 1 , comprising:

- reacting a boronate ester with a second reactant selected from the group consisting of polyfunctional diol, polyfunctional diamine, polyfunctional amino alcohol, polyfunctional thiol.

6. A process according to claim 4, comprising:

- depositing the second reactant onto said surface prior to the polyfunctional boronic acid, so as to prevent the polyfunctional boronic acid from reacting with itself.

7. A process according to one of claims 4 or 5, comprising:

- co-depositing the polyfunctional boronic acid or boronate ester and the second reactant at the same time onto said surface.

8. A process according to one of claims 1 to 7, comprising:

- depositing the polyfunctional boronic acid or the boronate ester and the second reactant under ultra high vacuum and by sublimation of the reactants.

9. A process according to one of claims 1 to 8, comprising:

- adding functional substituents to the reactants prior to deposition onto said surface.

10. A process according to one of claims 1 to 9, comprising a further step of incorporating heterocyclic macrocycles into the network.

11. A process according to one of claims 1 to 10, comprising a further step of selectively depositing a material in pores of the porous covalent organic network.

12. A process according to one of claims 1 to 11 , wherein the reactants are deposited onto an oriented crystalline surface.

13. A process of manufacturing a network of nanoparticles onto a surface, comprising:

- synthesizing a porous covalent organic monolayer network onto the surface according to the process according to one of claims 1 to 12, and

- selectively depositing a material in pores of the porous covalent organic network.

14. A process according to claim 14, comprising a further step of removing the network.

15. A covalent ordered monolayer on a surface, characterized in that it comprises a boroxine-linked or a boronate-linked network and has a two- dimensional nano-meter scale porous structure.

16. A covalent ordered monolayer on a surface, wherein the boroxine- linked or boronate-linked network comprises a predominance of structured pores.