Fabrication of high-degradation-efficiency molecularly imprinted photocatalysts and its selective degradation performance

doi:10.3724/SP.J.1123.2025.06001

Abstract

Abstract:

Molecularly imprinted photocatalysts （MIPCs）， which integrate specific molecular recognition with photocatalytic degradation capabilities， hold great promise for the selective and efficient removal of trace pollutants from complex environmental matrices. However， conventional surface-imprinting layers coated on photocatalysts often cause light-shielding effects， thereby reducing the photocatalytic efficiency of MIPCs. To overcome this limitation， the present study proposes a heterojunction-based interfacial in-situ imprinting strategy. In this approach， molecular imprinting cavities are directly constructed at the interface of composite photocatalysts. This design not only avoids the negative impact of surface shielding but also facilitates interfacial charge transfer， thus achieving a synergistic enhancement of both molecular recognition selectivity and photocatalytic efficiency. Based on this concept， a highly efficient molecularly imprinted photocatalyst， BiOBr-Cu/ppyr-MIPs， was successfully fabricated. The synthesis utilized surface molecular imprinting technology with the organic pollutant acid orange （AO） as the template molecule， and BiOBr-Cu/polypyrrole （ppyr） composite as the heterojunction matrix. Polypyrrole， introduced as a conductive polymer， served as the imprinting layer that promotes charge migration. The synthesis conditions， including monomer amount and polymerization time， were systematically optimized to maximize imprinting efficiency and photocatalytic performance. The obtained BiOBr-Cu/ppyr-MIPs were comprehensively characterized. Scanning electron microscopy （SEM） revealed a well-defined morphology with uniformly distributed imprinted layers. X-ray diffraction （XRD） analysis confirmed that the introduction of the polypyrrole-based imprinting layer did not significantly alter the crystal structure of the BiOBr-Cu composite. Fourier-transform infrared spectroscopy （FTIR） showed characteristic peaks attributable to the pyrrole ring， such as C-H in-plane bending， C-H stretching， and C=N stretching vibrations， indicating successful incorporation of the polypyrrole framework. X-ray photoelectron spectroscopy （XPS） further confirmed the formation of the imprinted layer， with increased proportions of C-N and O=C bonding components observed in the C 1s and O 1s spectra， respectively. Optical and photoelectronic properties were also evaluated. UV-vis diffuse reflectance spectroscopy （DRS） revealed a significant red-shift and broader light absorption in the visible range， attributed to the presence of the polypyrrole layer. Photoluminescence （PL） spectroscopy demonstrated a marked decrease in emission intensity， indicating that the recombination of photogenerated electron-hole pairs was effectively suppressed， which correlates with enhanced charge separation. Adsorption experiments indicated that BiOBr-Cu/ppyr-MIPs exhibited rapid adsorption kinetics， reaching equilibrium within 30 min and fitting a pseudo-second-order kinetic model. The maximum adsorption capacity was determined to be 40.9 μmol/g， consistent with the Freundlich isotherm model， suggesting a heterogeneous adsorption process with multilayer adsorption behavior. Photocatalytic degradation studies， optimized by adjusting catalyst dosage， initial pollutant concentration， and solution pH， showed a 2.04-5.79-fold enhancement in degradation efficiency compared to reference materials. The composite also exhibited excellent reusability， maintaining 90.7% of its initial performance after five consecutive cycles. Importantly， the material demonstrated strong molecular recognition capability， with an imprinting factor （IF） of 2.96 and a selectivity coefficient （K_selectivity） exceeding 1.79， indicating effective discrimination between the template molecule and structural analogs. Mechanistic investigations revealed that the interfacial polypyrrole imprinting layer not only contributed to selective adsorption but also facilitated targeted degradation pathways， thus achieving integrated selectivity and catalytic activity. In summary， this work introduces a novel interfacial in-situ imprinting strategy that overcomes key limitations of conventional MIPCs. The proposed design offers a generalizable approach for developing molecularly imprinted photocatalysts with both superior degradation efficiency and selectivity.

Key words: molecular imprinting, selective removal, polypyrrole, bismuth oxobromide

CLC Number:

O658

ZHANG Junjie, SONG Yafei, LIU Yan, TIAN Xuemeng, GAO Ruixia. Fabrication of high-degradation-efficiency molecularly imprinted photocatalysts and its selective degradation performance[J]. Chinese Journal of Chromatography, 2026, 44(1): 78-91.

Figures/Tables 16

Fig. 1 Synthesis process of BiOBr-Cu/ppyr-MIPsPVP： polyvinylpyrrolidone； EG： ethylene glycol； AO： acid orange； pyr： pyrrole； TRIM： trimethylolpropane trimethacrylate； pro-ppyr-MIPs： polypyrrole surface molecularly imprinted photocatalysts without elution.

Fig. 2 （a） Effect of the amount of functional monomer pyr on the photocatalytic performance of the materials and （b） kinetic constants of BiOBr-Cu/ppyr-MIPs （n=3）

Fig. 3 （a） Effect of the polymerization time on the photocatalytic performance of the materials and （b） kinetic constants of BiOBr-Cu/ppyr-MIPs （n=3）

Fig. 4 SEM images of （a） BiOBr-Cu and （b） BiOBr-Cu/ppyr-MIPs

Fig. 5 （a） XRD patterns and （b） FTIR spectra of BiOBr-Cu and BiOBr-Cu/ppyr-MIPs

Fig. 6 XPS spectra of BiOBr-Cu and BiOBr-Cu/ppyr-MIPs： high-resolution scan of （a） Bi 4f，（b） Br 3d，（c） C 1s， and （d） O 1s

Fig. 7 （a） UV-vis DRS and （b） PL spectra of BiOBr-Cu and BiOBr-Cu/ppyr-MIPsDRS： diffuse reflectance spectroscopy； PL： photoluminescence.

Fig. 8 （a） Adsorption kinetic，（b） pesudo-second-order kinetic models，（c） thermodynamics curves， and （d） Freundlich thermodynamics models of BiOBr-Cu/ppyr-MIPs and BiOBr-Cu/ppyr-NIPs （n=3） Qe： adsorption capacity at adsorption equilibrium； Ce： equilibrium concentration.

Fig. 9 （a） Effect of the amount of BiOBr-Cu/ppyr-MIPs on the photocatalytic performance and （b） first-order kinetics；（c） effect of the original AO mass concentration on the photocatalytic performance of BiOBr-Cu/ppyr-MIPs and （d） first-order kinetics （n=3）

Fig. 10 （a） Effect of the initial pH on the photocatalytic performance of BiOBr-Cu/ppyr-MIPs and （b） first-order kinetics （n=3）

Table 1 Comparison of AO photo-degradation efficiencies with various Bi-based photocatalysts

Materials	Dosage/ mg	Original AO mass concentration/（μg/mL）	Degradation rate/%	Degradation time/min	TOF/ （10^-5 min^-1）	Ref.
Ag-Ag₃O₄/Bi₄V₂O₁₁	100	10.0	99.5	180	5.53	［36］
Bi/Bi₄NbO₈Cl	40.0	20.0	99.9	180	11.1	［37］
Ppy/Bi₂MoO₆	50.0	50.0	94.3	480	15.7	［38］
BiOBr-Cu/ppyr-NIPs	15.0	20.0	41.4	120	13.8	this work
BiOBr-Cu/ppyr-MIPs	15.0	20.0	96.0	120	32.0	this work

Fig. 11 Reusability of BiOBr-Cu/ppyr-MIPs （n=3）

Fig. 12 Selectivity experiments of BiOBr-Cu/ppyr-MIPs and BiOBr-Cu/ppyr-NIPs （n=3） AR： allura red； RA： red amaranth； OG： orange G.

Table 2 Degradation rates and selectivity factors of AO and its competitors based on BiOBr-Cu/ppyr-MIPs and BiOBr-Cu/ppyr-NIPs

Analyte	η_MIPs/%	η_NIPs/%	k_imprinted	k_comparsion	k_selectivity
AR	45.5	35.0	2.11	1.18	1.79
RA	24.8	21.6	3.87	1.92	2.02
OG	21.8	23.6	4.40	1.75	2.51

Fig. 13 Effects of different scavengers on the photocatalytic performance of BiOBr-Cu/ppyr-MIPs （n=3）IPA： isopropanol； TEOA： triethanolamine； LAA： L-ascorbic acid sodium.

Fig. 14 （a） Electron transmission over BiOBr-Cu/ppyr-MIPs；（b） mass spectra of the photodegradation at initial （0 min） and 60 min；（c） possible pathway of AO photodegradation with BiOBr-Cu/ppyr-MIPsh+： hole； e-： electron； VB： valence band； CB： conduction band； HOMO： highest occupied molecular orbital； LUMO： lowest unoccupied molecular orbital； PPYR： poly-pyrrole layer. The band positions in Fig. 14a are referenced to the standard hydrogen electrode.

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