Efficient Photocatalytic Reduction of CO ₂ Catalyzed by the Metal–Organic Framework MFM-300(Ga)

Open AccessCCS ChemistryCOMMUNICATION5 Aug 2022Efficient Photocatalytic Reduction of CO2 Catalyzed by the Metal–Organic Framework MFM-300(Ga) Tian Luo, Zi Wang, Xue Han, Yinlin Chen, Dinu Iuga, Daniel Lee, Bing An, Shaojun Xu, Xinchen Kang, Floriana Tuna, Eric J. L. McInnes, Lewis Hughes, Ben F. Spencer, Martin Schröder and Sihai Yang Luo Department Chemistry, University Manchester, Manchester M13 9PL Google Scholar More articles this author , Wang Photon Science Institute (PSI), Han Chen Iuga Physics, Warwick, Coventry CV4 7AL Lee Chemical Engineering Analytical Science, An Xu Kang Chinese Academy Beijing 100190 Tuna McInnes Hughes Earth Environmental Sciences, Spencer Materials, *Corresponding authors: E-mail Address: [email protected] https://doi.org/10.31635/ccschem.022.202201931 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail reduction carbon fuels is an important target but highly challenging achieve. Here, we report efficient photoconversion into formic acid over a Ga(III)-based metal–organic framework (MOF) material using triethanolamine as sacrificial agent. Under light irradiation at room temperature, photoreduction yields with selectivity 100%, high productivity 502 ± 18 ?mol·gcat?1·h?1, excellent catalytic stability. In situ electron paramagnetic resonance spectroscopy reveals that promotes generation CO2•? radical anions reaction intermediate driven strong binding activation molecules bridging –OH sites within pore. This study represents first example MOF catalyst for reduction. Download figure PowerPoint Introduction The development photocatalysts convert value-added chemicals has attracted much interest.1,2 addition TiO2, various Ga-based semiconductors, such GaN, GaP, Ga2O3, ZnGa2O4, have been widely investigated drive reaction.3–7 However, their wide optical bandgap (Eg) restricts use solar mainly ultraviolet region, and, more importantly, nonporous nature limits mass transport CO2. impedes charge transfer between substrate also leads undesirable recombination photogenerated electrons holes.8 A number strategies exploited improve photocatalytic performance semiconductors. For example, doping metals (e.g., Ge, Zn) or nonmetals N, Si) can narrow light-harvesting efficiency resultant material.9–12 Fabrication ultrathin nanosheets, nanowires, porous structures increase surface area uptake.13–15 Meanwhile introduction cocatalyst, noble metal nanoparticles, second semiconductor construct Z-scheme heterojunction-type systems promote transfer.10,16–18 state-of-the-art semiconductors remains limited, only gaseous products CH4 CO are produced. top-performing heterostructure Au/Al2O3/p-GaN shows 230 ?mol·g?1·h?1.4 Metal–organic materials incorporate active fixed uniformly in 3D space, thus preventing aggregation centers potentially enhancing separation. MOFs therefore emerging CO2, showing potential overcome barriers conventional semiconductors.19,20 intrinsic microporosity catalytically confined form unique “microreactors” adsorption via formation host–guest interactions.21 backbone consisting infinite metal-ligand linkages facilitate ligand-to-metal-charge-transfer (LMCT), prolonging excitation lifetime boosting isolation utilisation photoinduced electrons.22 tested CO2,19,20 Ti-based particularly attractive.23,24 contrast, date, no shown exhibit activity conversion, here catalyzes conversion 100% up significantly higher than among best-behaving MOF-based reaction. Importantly, (EPR) confirms anion (CO2•?) generated production MFM-300(Ga). Results Discussion MFM-300(Ga), [Ga2(OH)2(L)] (H4L = biphenyl-3,3?,5,5?-tetracarboxylic acid) was chosen due its stability, adsorption, hydrogen bonds groups pore.25 comprised chains [GaO4(OH)2]? octahedra linked cis-?2-OH groups, these further bridged tetracarboxylate ligands ‘wine rack’ open framework. Desolvated Brunauer–Emmett–Teller (BET) 1064 m2·g?1 uptake 5.00 mmol·g?1 298 K 1 bar (see Supporting Information Figure S1). purity bulk confirmed powder X-ray diffraction (PXRD) S2) thermogravimetric analysis S3a). Scanning microscopy (SEM) transmission (TEM) show crystals cuboid-shaped morphology average size 15 ?m (Figure 1b). High-resolution photoelectron (XPS) peaks Ga 2p1/2, 2p3/2, 3d3/2, 3d5/2 1145.5, 1118.6, 21.2, 20.7 eV, respectively, consistent trivalent Ga(III) 1c, see S4). Solid-state 13C 71Ga NMR reveal ordered structure single repeating octahedral [GaO4(OH)2] environment S5).26 high-field 71Ga{1H} 2D through-space (dipolar) heteronuclear correlation spectrum demonstrates extensively correlations hydroxyls (at ?{1H} 2.8 ppm) weaker interaction distant aromatic proton carboxylates 9.0 ppm), other observed 1d). Moreover, ratio 1H signal intensities protons hydroxy ?3:1 S5c), entirely structural model Figures 1e–1h. UV–vis diffuse reflectance (UV-DRS) intensive broad absorption band which assigned ???* transition biphenyl ligand 1a).27 Tauc plot 3.30 lower commercial Ga2O3 (Eg 4.56, 4.70, 4.67 eV ?-, ?-, ?-Ga2O3, respectively)28 ZnGa2O4 4.18 eV).9 photocurrent response current density increases upon decreases turning off S6). | Characterisation crystal (a) UV-DRS (insert); (b) SEM image TEM (c) high-resolution XPS 2p, (d) D-HMQC MAS corresponding 1D direct (top) (left) spectra, recorded 20.0 T frequency 60 kHz; MFM-300(Ga): (e) [GaO4(OH)2]; (f) ligand; (g h) views (bridging groups) adsorbed studied synchrotron single-crystal diffraction.25 Host–guest intermolecular dipole interactions highlighted cyan yellow, respectively. toward CO2-saturated CH3CN-containing (TEOA) agent under 350–780 nm 1–12 h. were analysed gas chromatography liquid product spectroscopy. measured moles obtained per gram hour (mol·gcat?1·h?1) afford comparison reported catalysts. Formic detected phase, carbon-containing detected. function time indicates ?mol·gcat?1·h?1 achieved 4 h (Figures 2a, S7). crystallinity retained three cycles 2b). majority (Table 1) converting acid, amino-functionalised MIL-125(Ti), UiO-66(Zr), MIL-101(Fe),23,31,44 two cases. One mixed NH2-UiO-66(Zr/Ti) (NH2)2-UiO-66(Zr/Ti),24 prepared post-synthetic modifications introduce Ti(IV) recent describing ?-conjugated naphthoporphyrin system constructed Zr clusters, highest value (6630 ?mol·gcat?1·h?1) literature.29 studies thermal hydrogenation catalysts given Table S1. 2 Different time; recycling tests. Reaction conditions: (10 mg), TEOA/CH3CN (3 mL/15 mL, saturated CO2), 25 °C, nm, Comparison Efficiency Selection Reported Literature MOF-Based Materials Formula Uptake/mmol·g?1 (1 atm) Sacrificial Agent Solvents (?mol·gcat?1·h?1) References TNP-MOF Zr6(OH)4O4(TNP)3 1.69 (273 K) 1.03 (298 TEOA CH3CN 6630 29 NH2-UiO-66-Zr(Ti) (NH2)2-UiO-66-Zr(Ti) – Zr4.3Ti1.7O4(OH)4(C8H7O4N)5.17(C8H8O4N2)0.83 BNAH 782 1052 24 Ga2(OH)2(L) 6.77 work Co-MOF, LIFM-45 Co3(HL0)2·4DMF·4H2O DMAc 456 30 NH2-MIL-101(Fe) MIL-101(Fe) NH2-MIL-53(Fe) MIL-53(Fe) NH2-MIL-88(Fe) MIL-88(Fe) Fe3OCl(H2O)3(BDC-NH2)3Fe3OCl(H2O)3(BDC)3FeIII(OH)(BDC-NH2) FeIII(OH)(BDC) FeIII3O(CH3OH)3(BDC-NH2)3FeIII3O(CH3OH)3(BDC)3 1.52 1.18 0.89 0.60 0.64 0.46 445 148 116 74 75 23 31 AD-MOF-2 AD-MOF-1 [Co2(HAD)2(AD)2 (IA)2]·DMF [Co2(HAD)2 (AD)2-(BA)]·DMF·2H2O 1.86 2.33 TIPA 443 179 32 Fe3-Fe2-NH2Fe3-Fe2 [{Fe2-Tri}{Fe3(?3-O)(BDC-NH2)3}]·4NO3[{Fe2-Tri}{Fe3(?3-O)(BDC)3}]·4NO3 1.38 1.23 CH3CN/H2O (1:1) 396 309 33 PCN-138 [Zr6(?3-O)4(?3-OH)4][TCPP][TBTB]8/3 2.82 1.82 H2O 168 34 Ir-CP [Y(Ir(ppy)2(dcbpy)2][OH] 158 35 Eu-Ru(Phen)3 [Eu2(?2-H2O)(H2O)3(L1)2]·(NO3)2·(2-FBA)2·(H2O)22 94 36 Cd/Ru-MOF-1 Cd/Ru-MOF-2 {Cd3[Ru-L2]2·2(Me2NH2)·solvent}n {Cd[Ru-L3]·3(H2O)}n 67 72 37 PCN-222(Zr) Zr6(?3-OH)8(OH)8(TCPP)2 2.59 1.56 38 NNU-28(Zr) [Zr6O4(OH)4(L4)6]·6DMF 2.83 1.49 53 39 PCN-136 Zr6(?3-O)4(?3-OH)4(OH)6(H2O)6(HCHC) 2.72 44 40 Zr-SDCA-NH2 [Zr6O4(OH)4(L5)6]·8DMF 3.74 1.57 41 NNU-31-Zn Fe2Zn(?3-O)(TCA)2(H2O)3 1.65 26 42 NH2-MIL-125(Ti) MIL-125(Ti) Ti8O8(OH)4(BDC-NH2)6Ti8O8(OH)4(BDC)6 5.90 4.40 16 NH2-UiO-66-(Zr/Ti) NH2-UiO-66(Zr) (Zr/Ti)6O4(OH)4(BDC-NH2)6Zr6O4(OH)4(BDC-NH2)6 3.79 3.04 12 7 43 UiO-66(Zr) Zr6O4(OH)4(BDC-NH2)6Zr6O4(OH)4(BDC)6 2.37 0 Notes: TEOA, triethanolamine; BNAH, 1-benzyl-1,4-dihydronicotinamide; H4L, acid; H2BDC, benzene-1,4-dicarboxylic HAD, adenine; BA, butanedioic IA, isobutyric DMF, N,N-dimethylformamide; Tri, 1,2,4-triazole; DMAc, N,N-dimethylacetamide; TIPA, triisopropanolamine; H2TCPP, tetrakis(4-carboxyphenyl)porphyrin; TBTB, 4,4?,4?-(2,4,6-trimethylbenzene-1,3,5-triyl)tribenzoate; ppy, 2-phenylpyridine; dcbpy, 2,2?-bipyridine-4,4?-dicarboxylate; H4L0, 2?-amino-[1,1?:4?,1?-terphenyl]-3,3?,5,5?-tetracarboxylic H3L1, Ru(phen)3-derived tricarboxylate metalloligand; 2-FBA, 2-fluorobenzoate; L2=5,5?-dcbpy=2,2?-bipyridine-5,5?-dicarboxylate; L3=(4,4?-dcbpy)2(bpy), bpy=2,2?-bipyridine; H2L4, 4,4?-(anthracene-9,10-diylbis(e-thyne-2,1-diyl))dibenzoic HCHC, hexakis(4-carboxyphenyl)hexabenzocoronene; H2L5, 2,2?-diamino-4,4?-stilbene dicarboxylic TCA, 4,4?,4?-tricarboxytriphenylamine. To gain insights reaction, series control experiments conducted 2). No from reactions absence (1) (2) (where N2 used instead), (3) light. These results confirm source proceeds routes catalyst. Replacement triethylamine (TEA)45 gives low 64 reports on role assisting CH3CN.46,47 range different organic solvents tested, optimal enhanced CH3CN47 S8). Interestingly, when (?50 mesh, Eg 4.57), GaN 3.04), GaP 1.92), powdered mixture Ga(NO3)3 H4L photocatalyst S9). crucial separation electrons. Summary Conditions Experiments Entry Catalyst Light (nm) Gas HCOOH n.a. 3 5 6 TEA Ga(NO3)3·9H2O 8 9 10 11 MIL-53(Ga) MIL-68(Ga) entry 6, mL added replace TEOA; 7, (0.04 mmol, 16.7 mg) (0.02 6.6 (H4L, biphenyl-3,3,5?,5?-tetracarboxylic acid); 8–12, mg each investigate effects Ga-MOFs property, MIL-68(Ga), both terephthalic reaction.48–50 phase PXRD S10). bandgaps determined be 3.21 3.93 S11). same conditions above, neither Although similar BET areas (1117–1140 m2·g?1) comprising moieties, capacity (1.46–1.65 mmol·g?1) (5.00 S2). likely rigid presence ?2-OH crystallographic spectroscopic analyses.25 Furthermore, increased ?-electron delocalisation hence LMCT compared terephthalate MIL-68(Ga). collectively result drastic difference activity. Photophysical electrochemical understand redox properties Mott-Schottky (MS) valence-band determine positions conduction (ECB) valence (EVB) respectively.32,51 EVB 2.2 V versus normalised electrode (NHE) VB-XPS S12a). positive slope all MS plots frequencies typical n-type semiconductor, intercept independent frequency. flat (EFB) ?0.99 NHE S12b), usually ?0.1 ECB materials.52 Thus, estimated ?1.09 NHE. gap VB CB 3.29 agreement analysis. identify species involved process, spin-trapping EPR conducted. Since free radicals several orders magnitude shorter acquisition 5,5-dimethyl-1-pyrroline-n-oxide (DMPO) spin trap enable identification long-lived DMPO-radical adducts.53 intense six-line g 2.005 hyperfine coupling constants AN 15.2 G AH 18.9 unambiguously DMPO-CO2•?54,55 3a S3). acid. captured dark conditions. Significantly, best our knowledge, X-band spectra DMPO trap, (black) before (red) after irradiation, simulated (blue) major component, DMPO-CO2•? (green, simulation), minor DMPO-Ox (cyan, simulation) proposed mechanism cycle 3b). Upon activated, (2.2 V) promoted (?1.09 V), holes readily filled TEOA. Surprisingly, reductive reduce anions, strongly negative ?1.90 [Eq. (1)] process.56 through diffraction25 not bound activates molecules. shifts anodic potential. path regarded accepting simultaneously ?0.61 (2)].56 By molecule able accept bonding generate anion, unprecedented MOF-driven affords new Recently, impact host-guest demonstrated small catalysts.57,58 synergistic effect bandgap, rate transfer, most scaffold molecules, will inform design photocatalysts. + e ? ? • E 1.90 vs . H 0.61 Conclusion porosity flexibility MOFs, coupled photoelectrical properties, make them promising candidates We Ga-MOF-based temperature stability full retention Compared literature, plays reduction, sheds future improved available includes detailed experimental procedures characterization data. Conflict Interest There conflict interest report. Acknowledgments research supported EPSRC (EP/I011870, EP/V056409), Royal Society funding, funding National Facility Manchester. project received European Research Council Union’s Horizon 2020 innovation programme (grant 742401, NANOCHEM). UK High-Field Solid-State funded BBSRC (EP/T015063/1) well Warwick including partial Birmingham City Advanced Projects Advantage West Midlands Regional Development Fund. authors wish acknowledge Dr. Marek Nikiel help measurement. 1. Ran J.; Jaroniec M.; Qiao S. Z.Cocatalysts Semiconductor-Based Reduction: Achievements, Challenges, Opportunities.Adv. Mater.2018, 30, 1704649. 2. Zhang W.; Mohamed A. R.; Ong W. J.Z-Scheme Systems Carbon Dioxide Reduction:Where Are Now?Angew. Chem. Int. Ed.2020, 59, 22894–22915. 3. Dhakshinamoorthy A.; Navalon S.; Corma Garcia H.Photocatalytic TiO2 Related Titanium Containing Solids.Energy Environ. Sci.2012, 5, 9217–9233. 4. Li Cheng W.-H.; Richter M. H.; DuChene C.; Atwater H. 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