MULTIPLY FUSED PORPHYRIN POLYMER FILM COATED ON A SUBSTRATE

Abstract

A multiply fused, conjugated, porphyrin polymer film coated on a substrate, wherein the porphyrin monomer repeating units are di-meso-substituted porphyrins; and including a metal cation selected from the group consisting of Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(II), Pd(II), Ag(II), Pt(II) and Au(III), or mixtures thereof; the porphyrin units are multiply fused, including doubly-fused and/or triply-fused; including a substituent R attached to the meso position of the porphyrin monomer, the substituent R being an aromatic group presenting at least one free ortho position among; at least one of the two free ortho positions of the aromatic substituent is fused to the 13 position of the porphyrin monomer, the porphyrin polymer film being a porous porphyrin polymer film with mean pore diameters within the range of from 2 nm to 100 nm, and exhibiting a density not greater than 2 g/cm.sup.3. The invention also relates to a process for obtaining the multiply fused porphyrin polymer film coated on a substrate.

Claims

1.-13. (canceled)

14. A multiply fused, conjugated, porphyrin polymer film coated on a substrate, said multiply fused porphyrin polymer being of formula (I) ##STR00003## wherein: “n” is an integer greater than 1; the porphyrin monomer repeating units are di-meso-substituted porphyrins; M is a metal cation selected from the group consisting of Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(II), Pd(II), Ag(II), Pt(II) and Au(III), or mixtures thereof; the porphyrin units are multiply fused, including doubly-fused and/or triply-fused; each substituent R attached to the meso position of the porphyrin monomer is an aromatic group presenting at least one free ortho position among; and at least one of the two free ortho positions of the aromatic substituent R is fused to the β position of the porphyrin monomer, wherein the porphyrin polymer film is a porous porphyrin polymer film with mean pore diameters, determined by SEM, within the range of from 2 nm to 100 nm, and exhibiting a density, calculated from a measured surface density and the thickness of the film, not greater than 2 g/cm.sup.3.

15. The multiply fused, conjugated, polymer porphyrin film coated on a substrate according to claim 14, wherein the porphyrin monomer units are multiply fused, including one of doubly-fused β-meso, meso-β, and triply-fused β-β, meso-meso, β-β.

16. The multiply fused, conjugated, polymer porphyrin film coated on a substrate according to claim 14, wherein M is selected from at least one of Co(II) and Cu(II).

17. The multiply fused, conjugated, polymer porphyrin film coated on a substrate according to claim 14, wherein the mean pore diameters is within the range of from 5 nm to 80 nm, and, independently, the density is of from 0.20 g/cm.sup.3 to 1.5 g/cm.sup.3.

18. The multiply fused, conjugated, polymer porphyrin film coated on a substrate according to claim 14, wherein the n value of the porphyrin repeating units is from 2 to 50.

19. The multiply fused, conjugated, polymer porphyrin film coated on a substrate according to claim 14, presenting at least one of the following characteristics: a thickness of from 500 nm to 10 μm; an electrical conductivity of from 10.sup.−4 S/cm to 10 S/cm; a Young modulus of from 1 GPa to 3 GPa; and a water uptake of from 0.5 mg/mm.sup.3 of H.sub.2O to 1.0 mg/mm.sup.3 of H.sub.2O.

20. The multiply fused, conjugated, polymer porphyrin film coated on a substrate according to claim 14, wherein the aromatic group R is a 6-membered aromatic ring structure selected from the group consisting of at least one of phenyl, 4-pyridyl, 3-pyridyl, 4-methylphenyl (p-tolyl), 3,5-di-tert-butylphenyl, 4-hydroxyphenyl, 4-carboxyphenyl, 4-aminophenyl, 3-cyanophenyl, 4-trifluoromethyl-phenyl, 4-fluorophenyl, 3,5-bis(trifluoromethyl)phenyl, 4-chlorophenyl, 4-bromophenyl, naphthalene, anthracene, phenanthrene and pyrene.

21. A process for forming, on a substrate, a multiply fused, conjugated, porphyrin polymer being of formula (I) ##STR00004## wherein: “n” is an integer greater than 1; the porphyrin monomer repeating units are di-meso-substituted porphyrins; M is a metal cation selected from the group consisting of Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(II), Pd(II), Ag(II), Pt(II) and Au(III), or mixtures thereof; the porphyrin units are multiply fused, including doubly-fused and/or triply-fused; each substituent R attached to the meso position of the porphyrin monomer is an aromatic group presenting at least one free ortho position among; and at least one of the two free ortho positions of the aromatic substituent R is fused to the β position of the porphyrin monomer, wherein the porphyrin polymer film is a porous porphyrin polymer film with mean pore diameters, determined by SEM, within the range of from 2 nm to 100 nm, and exhibiting a density, calculated from a measured surface density and the thickness of the film, not greater than 2 g/cm.sup.3, the method comprising the steps of: providing a substrate in a vacuum chamber, performing on the substrate an oxidative chemical vapour deposition reaction with a predetermined quantity of at least one oxidant selected from FeCl.sub.3, CuCl.sub.2 and Cu(ClO.sub.4).sub.2, and a predetermined quantity of at least one porphyrin monomer of general formula (II): ##STR00005## wherein M is a metal cation selected from the group consisting of Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(II), Pd(II), Ag(II), Pt(II) and Au(III), or mixtures thereof; each substituent R attached to the meso position of the porphyrin monomer is an aromatic group presenting at least one free ortho position; wherein step (b) is carried at a substrate temperature range of from 150° C. to 250° C., and in that the ratio (r) of the at least one oxidant quantity/at least one porphyrin monomer quantity is within a range of from 35 to 150.

22. The process according to claim 21, wherein the r range is of from 45 to 125.

23. The process according to claim 21, wherein the temperature range of the substrate is of from 150° C. to 225° C.

24. The process according to claim 21, wherein step b) is further performed with at least one of: a crosslinking monomer being a mono-meso-substituted metalloporphyrin and/or an unsubstituted metalloporphyrin; and an octa-β-substituted metalloporphyrin which central metal cation is selected from the group consisting of at least one of Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(II), Pd(II), Ag(II), Pt(II) and Au(III).

Description

DRAWINGS

[0065] Other features and advantages of the present invention will be readily understood from the following detailed description and drawings among them:

[0066] FIG. 1 illustrates the diverse reactions occurring during the oCVD reaction of nickel(II) 5,15-diphenylporphyrin NiDPP with FeCl.sub.3, in accordance with various embodiment of the invention.

[0067] FIG. 2 is a schematic view of an example of oxidative chemical vapour deposition (oCVD) reactor for the deposition of conjugated porphyrins using FeCl.sub.3 oxidant, in accordance with various embodiment of the invention.

[0068] FIG. 3 is a graph showing the variation of the density of the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin thin films as a function of the substrate temperature, in accordance with various embodiment of the invention.

[0069] FIG. 4 represents Scanning electron micrographs of the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin thin films for different substrate temperatures, in accordance with various embodiment of the invention.

[0070] FIG. 5 represents photocatalytic H2 production rates for the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin thin films synthesized at different substrate temperatures, in accordance with various embodiment of the invention.

[0071] FIG. 6 shows the variation of the density of the fused copper(II) 5,15-(di-3,5-di-trifluoromethylphenyl)porphyrin thin films as a function of the ratio between FeCl.sub.3 and porphyrin monomer, in accordance with various embodiment of the invention.

[0072] FIG. 7 represents photocatalytic H2 production rates for the fused copper(II) 5,15-(di-3,5-di-trifluoromethylphenyl)porphyrin thin films as a function of the ratio between FeCl.sub.3 and porphyrin monomer, in accordance with various embodiment of the invention.

DETAILED DESCRIPTION

Film Characterizations

[0073] The electrical conductivity is measured by depositing the films onto commercial OFET chips. The measurements were done without applying any gate voltage and by recording the current-voltage scans with a two-point probe to extract the conductivity using Ohm's law. The thickness of the films was measured using an Alpha step d-500 profilometer from KLA-Tencor.

[0074] The surface density was assessed from the specific mass gain due to the deposition and the area of the coated surface: Surface Density [μg.Math.cm.sup.−2]=(m.sub.1−m.sub.0)/A, where m.sub.0 and m.sub.1 are the masses of the coated and uncoated substrate, respectively, while A is the coated area estimated using ImageJ software. Coated microscope glass slides were weighted using a microbalance (Sartorius ME36S) to obtain m.sub.1, then the samples were immersed in a mixture of acetone/ethanol (50:50%) for 2 min before to be cleaned using Kimtech tissues to remove all the deposited film and obtain m.sub.0. The surface density measurements were repeated on three different samples for each deposition condition to determine the average surface density. The film's density (g.Math.cm.sup.−3) was calculated from the measured surface density and the thickness of each film.

[0075] The static water contact angles (WCA) were evaluated from five different measurements undertaken at different position for each sample using a contact angle measuring instrument (KRÜSS EasyDrop).

[0076] The water uptake of the films was evaluated on coated glass substrates by measuring the mass difference of the totally hydrated (m.sub.wet) and vacuum-dried films (m.sub.dry). Initially, the water from the fully hydrated films was carefully blotted using Kimtech tissues, then dried in a vacuum oven at 70° C. for 24 h. The water uptake measurement was repeated five times for each of the prepared thin films and the average value and standard deviation of these measurements are reported.

[0077] The optical absorbance was measured in the range of 250-2500 nm using an UV/Vis/NIR spectrophotometer (Perkin Elmer, Lambda 950) with a 150 mm diameter integrating sphere. The absorbance of the as-deposited and acetone rinsed films was measured on the glass substrates. The absorbance of the acetone-soluble phase of the films was measured in quartz cuvettes of 3.5 mL and 1 cm light path. The Helium Ion Microscope (HIM) images were recorded with an Orion Nanofab Instrument from Zeiss. The images were acquired from samples deposited on silicon wafers. Helium ions are generated using a gas field ionization source (GFIS). Within the GFIS a sharp needle having an apex radius of approximately 100 nm is set to a positive high voltage with respect to an extraction electrode accelerating the ions. A landing energy of 30 keV was used, impinging an ion currents between 0.1 and 1 pA and a tilt angle of the substrate holder stage of 20°. The helium ion beam scans the sample surface creating secondary electrons (SE). Contrast in the images is created mainly by composition and topography. Compared to the standard secondary electron microscope (SEM), the HIM allows to probe specimens with a better surface sensitivity and a higher depth of field which makes it very suitable for topographic imaging. Images of the topography and nanomechanical properties (Young modulus) of the samples were acquired using the AM-FM mode of the MFP-3D Infinity Atomic Force Microscopy (AFM) (Asylum Research). All measurements were made under ambient conditions (room temperature and relative humidity of about 50%) and a standard cantilever holder for operation in air was used. Images of a 2×2 μm.sup.2 area were taken with a resolution of 256×256 pixels at a scan rate of 3 Hz. Cantilevers' spring constants used in this study were about 20-30 N.Math.m.sup.−1 (Olympus, AC160TS-R3). The first and second resonant frequencies for AC160TS-R3 cantilevers were about 238 kHz and 1.34 MHz, respectively. A relative calibration method was done to estimate the tip radius using a dedicated reference samples kit provided by Bruker (PFQNM-SMPKIT-12m). The deflection sensitivity and the spring constant of the cantilever was determined using the Thermal Tune method (based on measurement of the thermal noise) and the Sader method. The tip radius was adjusted to obtain the proper value of 2.7 GPa for the polystyrene reference, matching the deformation applied on the sample of interest. To ensure repulsive intermittent contact mode, the amplitude setpoint was chosen as A.sub.setpoint/A.sub.0=ca. 0.7 so that the phase is well fixed at 60° C. The reported average and standard deviation values of Young modulus and roughness (Ra) consider at least 3 images in each sample for reliable results.

[0078] Secondary ion mass spectrometry (SIMS) measurements were performed on a CAMECA NanoSIMS 50 using a Cs.sup.+ primary ion beam with an impact energy of 16 keV and a current of around 1.5 A on sample surface. The masses studied simultaneously in multicollection mode were .sup.12C, .sup.14N, .sup.35Cl and .sup.56Fe, .sup.12O. Images were acquired at a size of 40×40 μm and 256×256 pixels. Secondary electron (SE) images were recorded using the same SIMS instrument. Atmospheric-pressure laser desorption/ionization coupled with a high resolution mass spectrometer (AP-LDI-HRMS) was used for the characterization and identification of the oligomers produced by the oCVD reaction of porphyrin monomers with FeCl.sup.3.

[0079] HRMS analyses were performed with an LTQ/Orbitrap Elite™ Hybrid Linear Ion Trap-Orbitrap Mass Spectrometer from Thermo Scientific (San Jose, CA) coupled with an AP-LDI (ng) UHR source from MassTech Inc (Columbia, MA) with a 355 nm Nd:YAG laser. The as-deposited polyporphyrins thin films were directly probed, without any matrix deposition, by the laser following a spiral motion during 30 seconds per sample. An in-source decay (ISD) of 70 V was applied to the samples in order to prevent any formation of non-covalent polyporphyrins clusters that could interfere with the distribution of the polyporphyrins oligomers. A maximum injection time of 800 ms and a resolving power of 240,000 at m/z 400 within the normal mass range (m/z 300-2000) and the high mass range (m/z 1800-4000) were employed for the HRMS analyses.

[0080] X-ray photoelectron spectroscopy (XPS) analyses were performed on a Kratos Axis Ultra DLD instrument using a monochromatic Al Kα X-ray source (Zu=1486.6 eV) at a power of 105 W. Charge calibration was accomplished by fixing the binding energy of carbon (C 1s) to 285.0 eV.

[0081] The photocatalytic hydrogen evolution test is performed in a 250 mL glass reactor, using 200 mL of an aqueous solution with 10% of a sacrificial agent, such as alcohols, amines, carboxylic acids, especially EDTA. At the beginning of the test, N2 is bubbled for 10 min to remove the oxygen or adsorbed gases from the reaction media. After this, the reactor is illuminated with a solar simulator integrated with a Xe lamp of 450 W. The H2 produced is analyzed in a Thermo Scientific gas chromatograph coupled with a thermal conductivity detector every 30 min during 3 h.

Example 1: nickel(II) 5,15-diphenylporphyrin (NiDPP)

[0082] A series of fused porphyrin tapes thin films was prepared from the oCVD reaction of nickel(II) 5,15-diphenylporphyrin (NiDPP) and iron(III) chloride (FeCl.sub.3), commercially available. NiDPP is selected due to its proven ability to form multiply-fused porphyrin tapes in oCVD (see G. Bengasi; K. Baba; O. Back; G. Frache; K. Heinze; N. D. Boscher; “Reactivity of Nickel(II) Porphyrins in oCVD Processes-Polymerisation, Intramolecular Cyclisation and Chlorination”; Chem. Eur. J., 2019, 25, 8313-8320), while FeCl.sub.3 was previously demonstrated as a better choice to promote the dehydrogenative coupling of porphyrins over their undesired chlorination. FIG. 1 illustrates the diverse reactions occurring during the oCVD reaction of nickel(II) 5,15-diphenylporphyrin NiDPP with FeCl.sub.3. Alongside the targeted dehydrogenative coupling of NiDPP, which can form singly, doubly or triply-fused porphyrin tapes, chlorination and 7-extension via ring fusion can occur.

Example 2: Cobalt(II) 5,15-di(4-fluorophenyl) porphyrin

[0083] Fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin thin films were deposited on silicon wafers, microscope glass slides and conductive FTO-coated substrates from the oxidative chemical vapour deposition (oCVD) reaction of cobalt(II) 5,15-di(4-fluorophenyl)porphyrin (CoD.sub.4FPP) with FeCl.sub.3.

[0084] The oCVD reaction was performed in a stainless steel reaction chamber equipped with two crucibles used to simultaneously sublimate the porphyrin and the oxidant, as shown in FIG. 2. The crucibles were loaded with 10 mg of CoD.sub.4FPP and 500 mg of FeCl.sub.3, r=50, and heated to 250° C. and 150° C., respectively.

[0085] The oCVD reactor was also equipped with a dry scroll pump (Varian) and a turbomolecular pump (Leybold) to achieve high vacuum. A butterfly type throttling valve (VAT) and a microleak valve fed with argon (Air Liquide, 99.999%) were used to maintain the pressure to 10.sup.−3 mbar for the preparation of the thin films. Under these conditions, FeCl.sub.3, was sublimated in ca. 50-fold excess with respect to the porphyrin monomer. Taking advantage of the solvent-free conditions of the oCVD method, different substrate temperatures, also called reaction temperature, were investigated. In particular, the substrate temperature was varied from room temperature (ca. 25° C.) to 200° C.

[0086] Irrespective of the substrate temperature, the oCVD reaction of CoD.sub.4FPP and FeCl.sub.3 yields the formation of macroscopically smooth and uniform thin films with an electrical conductivity in the range of 10.sup.−3 to 10.sup.−1S.Math.cm.sup.−1. The oCVD thin films exhibit colorations that strongly differ from the light orange color of the reference thin film prepared from the sublimation of CoD.sub.4FPP without oxidant. Such a color change is indicative of the formation of fused porphyrin tapes. Nevertheless, the discrepancy between the greenish coloration of the oCVD thin films elaborated at 25° C. and the dark brownish color of the oCVD thin films obtained at 200° C. hints on a difference in the deposition rate and/or in the reactivity, i.e., different reaction kinetics between the dehydrogenative coupling, chlorination and π-extension via ring fusion of the porphyrins. Interestingly, ultraviolet-visible-near infrared (UV/Vis/NIR) spectrophotometry evidenced a slightly more pronounced NIR absorption with the increase of the substrate temperatures, suggesting a higher degree of conjugation for higher substrate temperatures. Atmospheric-pressure laser desorption/ionization high-resolution mass spectrometer (AP-LDI-HRMS) analysis confirm the successful oxidative polymerization of CoD.sub.4FPP, i.e., intermolecular dehydrogenative coupling, irrespective of the substrate temperature. In addition, AP-LDI-HRMS also evidences chlorination (+Cl—H).sub.n and intramolecular cyclisation (—H.sub.2).sub.n reactions known to occur during the oCVD of porphyrins. Intramolecular cyclisation, i.e., intramolecular dehydrogenative coupling, occurs between the free ortho position of the 4-fluorophenyl substituent and beta position of the porphyrin macrocycle. Although AP-LDI-HRMS analysis does not provide an exhaustive view into the mass distribution and that the intensities related to the different species detected are not fully related to their abundance, the high mass resolution (up to 240,000 at m/z 400) and the high mass accuracy of the technique, around 3 ppm, enables the draw of informative trends. In particular, the analysis of the dimeric and trimeric regions of the spectra reveals the incorporation of a greater number of chlorine (+Cl—H).sub.n upon increase of the substrate temperature from 25° C. to 100° C. Surprisingly, a lesser amount of chlorine is integrated to the polymer structure upon further increase of the temperature to 200° C. On the other hand, the number of unsaturation in the molecule (−2H).sub.n, related to both intermolecular and intramolecular dehydrogenative coupling, is constantly increasing with an increase of the substrate temperature.

[0087] Contact profilometry measurements highlighted strong discrepancies between the thicknesses of the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin films. Indeed, while an identical amount of reactants is delivered to the substrate, thickness of the formed thin films varied from over 1 order of magnitude. In particular, thickness increased from 50 nm to 1.5 μm upon increase of the substrate temperature from 25° C. to 200° C. Surprisingly, in spite of the large growth rate discrepancies observed for the oCVD thin films, their weight per unit area was shown constant for all the investigated substrate temperatures, an almost identical to the weight per unit area of the reference thin film prepared from the sublimation of CoD4FPP without FeCl.sub.3. Such observation is consistent with the sublimation of identical amounts of porphyrin during the preparation of the thin films, but suggests strong variations in the density of the films. Indeed, the calculated density is shown to drastically decrease with increase of the substrate temperature. As shown in FIG. 3, the density calculated for the thin film elaborated at 200° C. (ca. 0.21 g.Math.cm.sup.−3) being over 20 times smaller than the one calculated for the thin film elaborated at 25° C. (ca. 4.8 g.Math.cm.sup.−3), and evidences the formation of highly porous thin films when employing large excess of oxidant and high substrate temperatures.

[0088] The decrease of the film's density is coupled to a decrease of the Young's modulus. In particular, the Young modulus value decreases from 5±1 GPa for the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin films prepared at 25° C. to 1.5±0.5 GPa for fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin films prepared at 200° C. Helium ion microscopy illustrated the formation of mesoporous thin films at high substrate temperatures, while denser layers are formed below 100° C., as depicted in FIG. 4. FIG. 4 for 200° C. shows some pores which are exhibiting various forms.

[0089] The low density and mesoporous structure of the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin films elaborated at the highest temperatures, is responsible of a greater water uptake for these samples. Specifically, water uptake between 0.8 mg/mm.sup.3 to 1.0 mg/mm.sup.3 are measured for the films elaborated at temperatures comprised between 150° C. and 200° C. It is worth noting that irrespective of the deposition condition, the water contact angle of the as-deposited fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin films remained fairly constant to 90°.

[0090] Upon exposure to visible light irradiation (Xenon lamp, 450 W), the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin films evolved hydrogen when immersed in a water solution containing 10% of ethylenediaminetetraacetic acid (EDTA). Interestingly, the photocatalytic catalytic performances of the fused cobalt(II) 5,15-di(4-fluorophenyl) porphyrin thin films directly correlated with their density and superior hydrogen production rates were achieved for the thin films prepared at 200° C. (FIG. 5). The formation of fused porphyrin thin films with highly porous structure, characterized by a density lower than 1 g.Math.cm.sup.−3, enabled to maximize the yield of the photocatalytic reaction.

Example 3: Copper(II) 5,15-(di-3,5-di-trifluoromethylphenyl)porphyrin

[0091] Fused copper(II) 5,15-(di-3,5-di-trifluoromethylphenyl)porphyrin films were deposited on silicon wafers, microscope glass slides and conductive FTO-coated substrates from the oxidative chemical vapour deposition (oCVD) reaction of copper(II) 5,15-(di-3,5-di-trifluoromethylphenyl)porphyrin (CuDDTFMPP) with FeCl.sub.3.

[0092] The oCVD reaction was performed with the reaction chamber described in Example 2.

[0093] The pressure was 10.sup.−3 mbar and the substrate temperature was 200° C. for all the deposition experiment duration, i.e., 30 min. The CuDDTFMPP was heated at 270° C., while the FeCl.sub.3 crucible temperature was varied from 80° C. to 200° C. in order to investigate different oxidant to porphyrin ratios, i.e., r of from 1 to 200.

[0094] The oCVD thin films exhibit colorations that strongly differ from the oxidant to porphyrin ratio. The thin film elaborated at the lowest r, of from 1 to 10, exhibit an orange coloration close to the one of the reference thin film prepared from CuDDTFMPP without oxidant, which suggests a low degree of polymerization for low oxidant to porphyrin ratios. This is not surprising as the high sticking coefficient of porphyrins implies that they can deposit on the substrate and form a thin film even if non-polymerised.

[0095] For r>10, the CuDDTFMPP-based films exhibit a green coloration that gets darker upon further increase of the oxidant to porphyrin ratio. Such a color change is indicative of the intermolecular dehydrogenative coupling of the CuDDTFMPP porphyrins, such as confirmed by AP-LDI-HRMS. AP-LDI-HRMS also evidenced the chlorination and 7-extension via ring fusion of the porphyrin tapes, which both get more pronounced upon increase of the oxidant to porphyrin ratio. As a consequence, the electrical conductivity of the CuDDTFMPP-based films is strongly affected by the oxidant to porphyrin ratio and varies for example from 10.sup.−9 to 10.sup.−4 S.Math.cm.sup.−1 for the films elaborated with an r of 1 and 50, respectively.

[0096] Contact profilometry measurements highlighted strong discrepancies between the thicknesses of the CuDDTFMPP-based films. In particular, thickness increased from 50 nm to 2.0 μm upon increase of the oxidant to porphyrin ratios from 1 to 200, the highest thickness values of the range is for high r.

[0097] While an identical amount of porphyrin is delivered to the substrate, such as confirmed by the almost identical weight per unit area of the thin films prepared from the different r investigated, these thickness discrepancies evidence strong variation of the CuDDTFMPP-based films density, as illustrated in FIG. 6. The density calculated for the thin film elaborated at r greater than 50 (ca. 0.20 g.Math.cm.sup.−3) being over 25 times smaller than the one calculated for the thin film elaborated at oxidant to porphyrin ratios lower than 5 (ca. 5 g.Math.cm.sup.−3) and suggest the formation of highly porous thin films when employing large excess of oxidant and high substrate temperatures. The decrease of the film's density is coupled to a decrease of the Young's modulus, which decreases from 5±1 GPa to 2±0.5 GPa upon increase of the oxidant to porphyrin ratios from 1 to ratios higher to 50.

[0098] Owing to the presence of the trifluoromethyl groups, the water contact angle of the CuDDTFMPP-based films is slightly hydrophobic with values comprise between 90° and 110°. Nevertheless, the CuDDTFMPP-based films are demonstrated to uptake water with an extend that depend on the used oxidant to porphyrin ratios. The highest water uptakes (up to 1.0 mg/mm.sup.3) being obtained for films prepared from oxidant to porphyrin ratios of from 50 to 100. For oxidant to porphyrin ratios superior to 150, delamination of the films occurs upon immersion in water.

[0099] Upon exposure to visible light irradiation (Xenon lamp, 450 W), the CuDDTFMPP-based films immersed in a water solution containing 10% of ethylenediaminetetraacetic acid (EDTA) exhibited hydrogen production rates that strongly depend on the oxidant to porphyrin ratio. Interestingly, as seen in FIG. 7, the photocatalytic catalytic activity of the CuDDTFMPP-based thin films reached a maximum for r of from 50 to 100. In spite of a similar degree of polymerization, CuDDTFMPP-based films elaborated for r of 25 exhibited a much lower photocatalytic activity, which is attributed to the lower specific surface area of this sample.

[0100] For r>150, a collapse of the photocatalytic activity is observed. Such a decrease of the photocatalytic properties is attributed to the cracking and decohesion of the CuDDTFMPP-based thin films related to the excess of oxidant and oxidant by-products trapped into the thin films and dissolved upon immersion in aqueous media.