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  • Contents lists available at ScienceDirect

    Chemical Engineering Journal

    journal homepage: www.elsevier.com/locate/cej

    Light-responsive UiO-66-NH2/Ag3PO4 MOF-nanoparticle composites for the capture and release of sulfamethoxazole

    Xue-Yan Xua, Chun Chua, Huifen Fua, Xue-Dong Dua, Peng Wanga, Weiwei Zhengb, Chong-Chen Wanga,⁎

    a Beijing Key Laboratory of Functional Materials for Building Structure and Environment Remediation, Beijing University of Civil Engineering and Architecture, Beijing 100044, PR China bDepartment of Chemistry, Syracuse University, Syracuse, NY 13244, United States

    H I G H L I G H T S

    • The MOF-nanoparticle (UiO-66-NH2/ Ag3PO4) composites was facilely fab- ricated.

    • The light-responsive MOF-NP compo- sites for SMX capture and release was reported.

    • The SMX release from composites was controlled by the size of nano-Ag3PO4 on MOF.

    • Mechanism of the light-triggered SMX release was clarified.

    G R A P H I C A L A B S T R A C T

    A R T I C L E I N F O

    Keywords: Light-response MOF-nanoparticle composites Desorption UiO-66-NH2 PPCPs Mechanism

    A B S T R A C T

    Light-responsive materials are attracting increasing amount of attention and have great potential in many re- search fields in environmental chemistry, materials science, biology, and nanotechnology. In this work, UiO-66- NH2/Ag3PO4 (UAP-X) Metal-organic framework (MOF)-nanoparticle composites with remarkable adsorption performance toward sulfamethoxazole (SMX) were reported. In addition, visible light-triggered release of SMX in the UAP-X composites was reported for the first time. It is believed that the light-triggered desorption of SMX is due to the transformation from Ag+ to Ag0 in the light-sensitive Ag3PO4 nanoparticles (NPs) of the composites. The SMX release performance of UAP-X can be tuned by the size of Ag3PO4 NPs distributed on the UiO-66-NH2. Specifically, the smaller crystal size of Ag3PO4 NPs, which can facilitate the reduction of Ag+ to Ag0, can be achieved with an increase in relative UiO-66-NH2 content in the composites. In addition, the higher UiO-66-NH2 content of the composite could provide more deposition area to minimize the aggregation of Ag3PO4, which could further enhance the reduction of Ag+. The light triggered desorption provides new possibility to achieve pollution-free and low-cost recyclability of adsorbents.

    1. Introduction

    Pharmaceuticals and personal care products (PPCPs) are widely used and essential in daily life. However, the extensive applications and

    poor elimination of PPCPs by the conventional biological wastewater treatment plants lead to the contamination of surface water and even ground water [1,2]. The bioaccumulation of these pseudo persistent PPCPs in the aquatic life can exert serious threat to the environment

    https://doi.org/10.1016/j.cej.2018.06.005 Received 3 May 2018; Received in revised form 29 May 2018; Accepted 1 June 2018

    ⁎ Corresponding author. E-mail addresses: chongchenwang@126.com, wangchongchen@bucea.edu.cn (C.-C. Wang).

    Chemical Engineering Journal 350 (2018) 436–444

    Available online 02 June 2018 1385-8947/ © 2018 Elsevier B.V. All rights reserved.

    T

    http://www.sciencedirect.com/science/journal/13858947 https://www.elsevier.com/locate/cej https://doi.org/10.1016/j.cej.2018.06.005 https://doi.org/10.1016/j.cej.2018.06.005 mailto:chongchenwang@126.com mailto:wangchongchen@bucea.edu.cn https://doi.org/10.1016/j.cej.2018.06.005 http://crossmark.crossref.org/dialog/?doi=10.1016/j.cej.2018.06.005&domain=pdf

  • and ecosystem [3,4]. Sulfamethoxazole (SMX) is a type of sulfonamide (SA) that is widely used in human and veterinary pharmaceuticals to prevent and/or treat disease such as diminishing inflammation and to promote livestock growth [5]. Considering their widespread con- sumption, high stability in aquatic media, and low biodegradability, SAs are considered a substantial ecotoxicological threat to aquatic flora and fauna and to human health [6].

    Up to now, various methods including photodegradation [7,8], coagulation-flocculation [9], biodegradation [10], chlorination [11], advanced oxidation processes (AOPs), ozonation [12,13] and adsorp- tion [14–19], have been adopted to eliminate PPCPs from the drinking water or wastewater. The removal of PPCPs by adsorption has been drawing significant interest as it is simple and cost effective. Metal- organic frameworks (MOFs) are particularly attractive adsorbents due to their unprecedented internal volume providing a large storage ca- pacity [20–22], and tunable framework chemistries offering a pathway to tailor release properties [23,24]. Hill and coworkers coated an op- tical fiber with a stable UiO-66, in which an anticancer drug 5-fluor- ouracil (5-FU) was loaded using a sublimation procedure [23]. The release of 5-FU into the surrounding solution was triggered by 1050 nm light. Zhou and co-workers synthesized PCN-123 to achieve reversible alteration of CO2 capture upon photochemical and thermal treatment [25]. The combination of the high surface areas of MOFs with nano- particles are an emergent class of composite materials. The unique size and surface effect of nanoparticle [26,27] with desirable photo-physical behavior can lead enhanced properties of MOF-NP composites [28]. For example, Ag3PO4 semiconductor NPs are an active visible-light-driven photocatalyst for dye degradation and oxygen evolution from water splitting [29,30].

    It should be noted that conventional adsorption is usually a spon- taneous process, hence desorption generally needs chemical or energy input. Recently, stimuli-responsive materials have attracted extensive attention for their potential applications in adsorption and other pro- cesses based on molecular logic systems [31–33]. Among various sti- muli including heat, pH, light, magnetic and electric fields, light is highly desired and has many advantages because of (1) finely tunable with high spatial and temporal accuracy, (2) non-invasive to the en- vironment on demand, (3) free of transport limitations, (4) no by-pro- duct generation, and (5) abundant sunlight available [31–33]. How- ever, light-response MOF-NP composites are less explored and MOF- Ag3PO4 composites have not been reported to the best of our knowl- edge.

    In this paper, a series of UiO-66-NH2/Ag3PO4 composites (UAP-X, X= 20mg, 35mg, 50mg, 120mg and 200mg UiO-66-NH2 in the composites) were synthesized in aqueous solution via an in-situ ion- exchange deposition/precipitation method using AgNO3, Na2HPO4·12H2O and UiO-66-NH2 as precursors. By the combination of the light-sensitive Ag3PO4 to UiO-66-NH2, the resulting UAP-X com- posites demonstrated enhanced adsorption and desorption toward SMX under dark and visible-light conditions. To the best of our knowledge, it is the first report that MOF-NP composite was utilized to conduct light- triggered desorption toward organic matters.

    2. Experimental

    2.1. Materials and instruments

    All chemicals were used directly as received without further pur- ification. Powder X-ray diffraction (PXRD) patterns of the samples were obtained with a Dandonghaoyuan DX-2700B diffractometer in the range of 2θ=5°–90° with Cu Kα radiation. Thermogravimetric analysis (TGA) were performed from 70 to 800 °C in an air stream at a heating rate of 10 °C/min on a DTU-3c thermal analyzer using α-Al2O3 as a reference. The Fourier transform infrared (FTIR) spectra were recorded from KBr pellets on a Nicolet 6700 spectrometer in the range of 4000–400 cm−1. The surface area of the sample was obtained from N2

    adsorption-desorption isotherms at 77 K using the Brunauer-Emmett- Teller nitrogen absorption method (BET, BELSORP-Mini II). The morphologies of the samples were observed using a JEM 1200EX transmission electron microscopy (TEM) and JEOL JSM-6700F scan- ning electron microscope (SEM). X-ray photoelectron spectra (XPS) measurement was performed on a Thermo ESCALAB 250XI. An Acquity UPLC H-Class (Waters) was used to detect the concentration of the SMX in solution after adsorption-desorption experiment at 274 nm. The analytes were separated by a C18 (1.7 μm, 2.1×50mm) on UPLC equipped with a TUV detector. Acidified water (0.1% formic acid, v/v) and methanol were used as mobile phase A and B, respectively. Gradient was programmed as the following: 0min, 10% B; 4.0min, 10% B; 5.5 min, 65% B, 6.0min 10% B. The column temperature was maintained at 313 K. A 6530 Q-TOF LC/MS (Agilent Technologies) was used to detect the SMX released from the UAP-X after adsorption-des- orption. The 6530 Q-TOF LC/MS was equipped with a Dual AJS elec- trospray ionization source (ESI). Parameters for analysis were set in both positive and negative ion modes. The optimal values of the ion source parameters were: capillary, +3500 V; drying gas temperature, 523 K; drying gas flow, 7.0 L/min; nebulizer pressure, 35 psi; shealth gas temperature, 598 K and shealth gas flow, 11.0 L/min.

    2.2. Synthesis of UiO-66-NH2/Ag3PO4 composites

    The UiO-66-NH2 was prepared according to a reported method by Karl Petter Lillerud and coworkers with a small modification [34]. Briefly, 0.81 g (4.5 mmol) NH2-BDC and 1.05 g (4.5 mmol) ZrCl4 were dissolved in 40.0 mL DMF. Then 17.0 mL (0.3mmol) acetic acid was added as a modulator. After that, the suspension was transferred to a Teflon-lined stainless steel autoclave and heated at 135 °C for 24 h. After the solvothermal reaction, the autoclave was slowly cooled down to room temperature. After separation from the solution via cen- trifugation, white solid products were ultrasonically washed with dis- tilled water several times, then re-collected and dried under 60 °C in an oven.

    UiO-66-NH2/Ag3PO4

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