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Novel carbonized polydopamine adsorbents (C-PDAs) with high surface area, high CO2 adsorption capacity and superior moisture resistance performance were prepared by one-step synthesis method using polydopamine as carbon precursor at different KOH/C ratios, and then characterized. CO2 and water vapor adsorption performances of C-PDAs were examined separately by static adsorption and fixed-bed experiments. Results showed that BET area and pore volume of C-PDA-4 were up to 3342 m2/g and 2.01 cm3/g, respectively. Its CO2 adsorption capacity reached up to 30.5 mmol/g at 25 bar, much higher than many other adsorbents including metal-organic frameworks (MOFs). C-PDAs prepared with high KOH/C ratios had low surface element concentrations of O and N resulting in low surface hydrophilic property. H2O(g) isotherm of C-PDA was much lower than those on Mg-MOF-74, Cu-BTC, and MIL-101(Cr). Fixed-bed experiments showed that co-presence of water vapor in feed stream with 30% RH had negligible impact on CO2 working capacity of C-PDA. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3730-3738, 2016 [ABSTRACT FROM AUTHOR]

Competitive adsorption and selectivity of benzene and water vapor were studied on the microporous metal organic frameworks (HKUST-1). The adsorption equilibrium and kinetics of pure component as well as binary mixtures of benzene and water vapor were systematically investigated on the HKUST-1. Their binary adsorption selectivity and permeation selectivity are predicted via the IAST method. Results showed that the equilibrium data of benzene and water vapor depicted the Langmuir–Freundlich and Dual Site Langmuir–Freundlich (DSLF) type adsorption isotherms, respectively. Benzene exhibited much higher isosteric heat and desorption activation energy than water vapor, indicating a stronger interaction with the HKUST-1. The adsorption selectivity of benzene/water on the HKUST-1 was of about ∼8.32 at 318 K and 1.0 mbar, and its diffusivity selectivity was about 17.6 at 298 K and 1.5 mbar, respectively. Breakthrough curves of benzene showed a remaining capacity of about 94.7% and 72.9% in the presence of 13 and 34 RH%. Thus, the HKUST-1 is more selective or preferential adsorption for benzene molecules in comparison to water molecules at high temperature and low pressure. Also, it shows the advantage of kinetic separation for VOCs and water vapor. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption and diffusion properties of p-xylene on the chromium-terphthalate-based crystals (MIL-101) and the surface energy of MIL-101 were investigated by using gravimetric and inverse gas chromatography (IGC) techniques. The nanocrystal MIL-101 (∼100nm) was synthesized by using microwave irradiation method. Adsorption isotherms and kinetic curves of p-xylene on the MIL-101 were measured at temperatures of (288, 298, 308 and 318) K and vapor pressures up to 6 mbar, respectively. Results show that the amount adsorbed of p-xylene on the synthesized MIL-101 was up to 10.9mmol/g at 288K and 6 mbar. The isosteric adsorption heat of p-xylene on the MIL-101 was in the range of 24.8–44.3kJ/mol, which decreased with an increase in amount adsorbed of p-xylene on the MIL-101. The diffusion coefficients of p-xylene within the MIL-101 were in the range of 2.80–10.1×10−10 cm2/s at 288–318K with activation energy of 30.9kJ/mol. Three polar probes (acetone, toluene and p-xylene) were used to characterize the surface property of the MIL-101 by using IGC technique. IGC measurement results showed that the specific component of the free energy of adsorption for polar probe molecules on the MIL-101 followed the order: p-xylene>toluene>acetone. [Copyright &y& Elsevier]

The role of reaction temperature in the structure of Zn(II)-1,4,-Benzendicarboxylic-MOFs (Zn-BDC-MOFs) and subsequently their CO2 adsorption properties were investigated. Crystal morphology and phase structure of the Zn-BDC-MOFs were characterized by SEM and PXRD. Stability and textual properties of the Zn-BDC-MOFs were analyzed by using accelerated surface area and porosimetry apparatus (ASAP) and thermogravimetric analysis (TG). Adsorption equilibrium and diffusion of CO2 on these materials were experimentally studied by the gravimetric method in the pressure range up to 1 atm at room temperature. Results showed that reaction temperature changed the coordination mode of 1,4,-Benzendicarboxylic acid ligand and caused the different structures and pore texture of Zn-BDC-MOFs. High reaction temperature was good for the generation of the three-dimensional MOFs with a higher adsorption capacity for CO2 but lower gas diffusivity. In contrast, low reaction temperature could cause the monodentate ligand in metal centers and form the low-dimensional MOFs with a lower adsorption capacity for CO2 but higher gas diffusivity. The order of CO2 adsorption uptake and diffusion time constant were given as MOF-130T > MOF-50T > MOF-100T > MOF-75T and MOF-50T > MOF-75T > MOF-100T > MOF-130T, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • HKUST-1 was grown on Cu-nanofiber to construct thermal-conductive HKUST-1@Cu-NF. • Self-transformation formed abundant thermal conductive adsorption sites in HKUST-1@Cu-NF. • Unsaturated Cu and microporous interface improved toluene adsorption compared to HKUST-1. • Thermal conductivity promoted heat transfer of HK@Cu-NF about >3 times than HKUST-1. • Adsorption and desorption rates of HK@Cu-NF were synchronously boosted ∼5–7 times. A major challenge in utilizing metal–organic frameworks (MOFs) for volatile organic compound (VOC) capture was their inclination for strong adsorption, which consequently impeded desorption and elevated energy demand. To overcome this challenge, the construction of HKUST-1@Cu nanofibers (HK@Cu-NF) with thermal conductive adsorption sites was proposed to synchronous enhance toluene adsorption and desorption efficiency for VOCs capture. In this work, Cu-based HKUST-1 was designed to grow on Cu nanofibers, and formed uniform coverage MOF layer with tight connection via homologous Cu self-transformation growth strategy. The synthesized composite was proved to maintain high surface area (1473 m2/g) and generate abundant unsaturated Cu sites on its nanointerface based from the thermally conductive Cu nanofibers. This unique connection structure endowed these adsorption sites with high affinity towards toluene and high thermal conductivity as well, and finally formed thermal conductive adsorption sites. As a result, HK@Cu-NF composite (80 % loading of HKUST-1) exhibited 1.9 times higher of toluene adsorption capacity at P / P 0 = 0.002 and >3 times higher of thermal diffusivity than pure HKUST-1. Furthermore, it achieved enhancement in both adsorption and desorption efficiency for toluene, which reached 4.8 and 6.9 times of pure HKUST-1. Therefore, construction of thermal conductive adsorption sites successfully improved the adsorption efficiency and regeneration efficiency for VOCs capture, and realized the low energy VOCs desorption process. [ABSTRACT FROM AUTHOR]

[Display omitted] • DABA with di-amino was introduced into MOF to construct duel-positive charge centers. • Dual-positive charge centers in MOF enhanced electrostatic interaction with toluene. • Amino in DABA formed weak affinity to H 2 O and then shielded H 2 O entry into Cr clusters in MIL. • D-MIL-101 showed high toluene uptake up to 4.69 mmol/g (3.1 times of MIL-101) at 500 ppm. • D-MIL-101 exhibited 3.3 times higher toluene work capacity than MIL-101 under 80% RH. Highly efficient capture of volatile organic compounds (VOCs) under humid conditions is a significant yet formidable task for metal–organic frameworks (MOFs). Based on the material simulation technique, we proposed implanting a significantly positive-density ligand (DABA) to modify MIL-101 and constructing dual positive-charging centers to improve MIL-101 competitive adsorption of benzene VOCs over H 2 O vapors both thermodynamically and kinetically. The introduction of DABA containing two –NH 2 groups with electrostatically positive charges into MIL-101 resulted in the formation of an open tetrahedral cage with a dual positive charging center. This facilitated strong N-H...π interactions with toluene molecules, leading them to accumulate firmly in MOF pores, and thus dramatically enhanced its adsorption capacity from 17 to 31 toluene molecules per unit cell compared to pristine MIL-101. Moreover, the open tetrahedral cage in D-MIL-101 preferentially captured toluene and occupied the strongest adsorption sites first, thus effectively preventing H 2 O entry into MOF pores to contact with hydrophilic metal sites. This realized high water resistance and toluene adsorption uptake under high humidity conditions. Results showed that D-MIL-101 had a high specific surface area of 2558 m2/g and a new microporous structure of 9.5 Å size. It presented higher toluene uptake of 4.69 mmol/g at lower vapor pressure of P / P 0 = 0.013 and 298 K temperature, as well as 3.3 folds higher working capacity of toluene compared to pristine MIL-101 under 80 % RH. This study presents a novel approach for constructing hydrophobic MOFs using new positive charging ligands and delves deeper into the competitive adsorption of VOCs/H 2 O in MOF composites for large-scale applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Carboxymethyl cellulose sodium (CMC) was used to in-situ synthesize foam HKUST-1. • CMC modulated HKUST-1 crystal into huge cubic shape (5.0 μm) with high surface area. • CMC embedded into foam HKUST-1 with Cu O clusters and formed a unique interface. • At P/Po ∼ 0.0026, foam HKUST-1 bared 5.2 times higher toluene uptake than MIL-101(Cr). • Chitosan modified foam HKUST-1 exhibited highest selectivity for acidic dipeptide. Abstract A green and in-situ metal-organic framework (MOF) shaping strategy was proposed to fabricate cellulose foam HKUST-1 and modify with polysaccharides for convenient adsorption applications. The obtained unique foam HKUST-1 not only maintains HKUST-1 intrinsic thermal stability and high surface area, but also exhibits unique crystal structure and interface for HKUST-1. Moreover, the surface and crystal size of foam HKUST-1s can be easily modulated with natural polysaccharides, and the crystal and novel interfaces awarded them 5.2 times higher adsorption uptake (4.52 mmol/g) for vapor-toluene than MIL-101 (Cr) under low pressure P/Po ≈ 0.0026 and high selectivity (1 0 7) for acidic/basic dipeptides EE/RR. Based on the above results, the novel foamed MOFs can be applied for volatile organic compounds (VOCs) adsorption under ambient condition and improve acidic dipeptides enrichment in liquid phase. It will play a significant role as adsorbent in practical adsorption applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • UiO-66 with defect pores and basic N surface was prepared by mechanochemistry. • Alkaline N-coordination to UiO-66 enhanced crystal stability under basic solution. • Alkaline N compounds formed sp2 and σ-π hybridization with Zr cluster in UiO-66. • N-doped UiO-66 showed high adsorption capacity and fast diffusion for rhodamine B. • N-doped UiO-66 exhibited 558 selectivity of RhB/ST (1:1 ratio), 223 times as UiO-66. Abstract Alkaline N-compounds (pyrrole, dopamine and 2-methylimidazole) were applied to induce crystal defects on UiO-66 via mechanochemical in-situ N-doping strategy and their role on its selective adsorption for cationic dyes i.e. rhodamine B (RhB) and safranine T (ST) were investigated systematically. Alkaline N-compounds coordination were proved to simultaneously modulate pore sizes and intensify surface alkalinity of the original UiO-66. The crystal defects constructed 3-D multi-point adsorption structure, which dramatically enhanced specific adsorption for RhB and ST in binary system. Results showed that pyrrole coordinated UiO-66 possessed 30% enhancement in surface area (1549.1 m2/g) with micropores at 9 and 12 Å (larger defects in UiO-66). Furthermore, temperature programmed desorption (H 2 O and NH 3) and corrosion resistance test concluded that N-doped UiO-66 possessed improved alkali-resistance and higher alkaline surface compared to pristine UiO-66. Separation performance revealed that pyrrole-doped UiO-66 showed two times enhanced adsorption capacity for RhB (384.1 mg/g), and 223 times higher selectivity for equimolar RhB/ST than that of parent UiO-66. Textural characterization, DFT simulation and electronic factors concluded that proper defect size and alkaline surface endow the novel defective UiO-66 excellent selectivity, adsorption and recycling performances. Thus, our in-situ N-doping strategy has guiding significance to design MOFs with special and useful defects for unique selective adsorption system beyond the circle of organic dyes on industrial level. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZIF-8 had the highest ACEI (CW) enrichment among five typical MOFs. • ZIF-8 had ultra-high selective adsorption for CW in simulated protein hydrolysate (α = 46.6). • ACE inhibitory activity increased 70.9 times after CW was desorbed by ZIF-8. • Interactions of MOFs and peptides are influenced by the electrostatic, CH/SH ··· π and molecular sizes. • ZIF-8 can achieve desorption of CW with a pH response in the range of 7.0–12.0. Searching adsorbents for high recognition and adsorption capacities of active peptides has become the hotspot of scientific research in the screening and purification of peptides. In this work, we selected MOFs materials with good biocompatibility to systematically investigated for the selective adsorption of highly active ACE inhibitory peptides. Herein, five typical kinds of metal organic frameworks (MOFs) were initially screened for their adsorption capacities towards di-peptide (CW) having ultra-high angiotensin-converting enzyme (ACE) inhibitory activity (IC 50 = 0.16 μM). The effects of their pore sizes and surface potentials on CW adsorption capacity were explored in this work. Among these MOFs, ZIF-8 was chosen as a di-peptide adsorbent due to its excellent adsorption capacity of CW (0.382 mmol/g). Besides, the adsorption behavior of ZIF-8 for di-peptides in the mixed solution was systematically explored. Experimental results indicated that ZIF-8 exhibited highly specific adsorption towards CW while showing very low and almost non-adsorption for the two inactive peptides, DD and RR. In their ternary peptide solution (molar ratio: CW/DD/RR = 1/10/10) for simulated protein hydrolysate, ZIF-8 displayed ultra-high adsorption selectivity (α = 46.6) for CW and thus enhanced almost 70.9 times the ACE inhibitory activity for the enriched solution. Meanwhile, molecular simulation revealed that ZIF-8 had high recognition towards CW, which was primarily attributed to synergistic mechanisms of electrostatic attraction, NH/SH ··· π interaction, and pore size screening of ZIF-8 towards CW. Interestingly, ZIF-8 was discovered for the first time to have a distinct pH-responsive property towards CW enrichment. Based on this property, pH-responsive adsorption was carried out with desorption over ZIF-8, and a stable regeneration process for 5 continuous adsorption/desorption cycles was accomplished. Collectively, this work proved that MOFs have promising application prospects in the field of peptide adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D COFs delivered inverse 1-PE/AP selectivity in organic phase. • Structure-performance relationships of COFs analogues were unraveled. • TpBZ-COF with moderate pore space showed the best separation performance. • The adsorption mechanism was investigated experimentally and theoretically. Adsorption is considered as a promising method to purify the mixed acetophenone (AP) and 1-phenylethanol (1-PE) that are generally difficult to separate. Many efforts have been made to improve the preferential uptake of AP over 1-PE in aqueous phase, but there exists a practical bottleneck associated with their limited aqueous solubility. Herein, we demonstrate unprecedented reversal of selectivity in the organic medium enabled by β-ketoenamine-linked covalent organic frameworks (COFs), which were fabricated successfully by polycondensation between 1,3,5-triformylphloroglucinol (Tp) and diamines. The dependence of selective adsorption ability toward 1-PE on pore size was firstly investigated experimentally, indicating that TpBZ-COF with moderate pore size outperformed other analogues. The adsorption behaviors of 1-PE and AP onto TpBZ-COF were examined systematically. The evaluation results revealed a strong affinity toward 1-PE versus AP as well as excellent stability in recycling experiments. Further, the dynamic breakthrough experiments confirmed the practical application potential and remarkable recyclability. To probe the mechanism and structure–activity relationship, an imine-linked COF possessing similar porous structure was used as a reference for comparison of separation performance both experimentally and theoretically. The occurrence of hydrogen bonding between the hydroxyl of 1-PE and β-ketoenamine-linkage as H-bond acceptor in suitable pore spaces endows TpBZ-COF a fantastic candidate for purifying 1-PE and AP from petrochemical by-products. [ABSTRACT FROM AUTHOR]

[Display omitted] • NH 2 -MIL(Ti)-125 was confined grown into via 'ship-in-the-bottle' synthesis approach by Ti-clusters anchored OMC. • Hydrophobic shell (OMC) enhanced surface non-polar and humidity resistance on MIL(Ti)@OMC Ti. • MIL(Ti)@OMC Ti achieved interconnected micro-/mesoporous networks and accelerated mass transfer. • MIL(Ti)@OMC Ti showed high moisture-resistance and adsorption affinity for toluene at ultra-low pressure. • the mechanism of selective toluene adsorption and recycling performance were deeply investigated. Competitive adsorption of volatile organic compounds (VOCs) under high humidity is a critical but challenging issue in the applications of metal–organic frameworks (MOFs). In this work, hydrophobic-shell structured NH 2 -MIL(Ti)-125@mesoporous carbon composite was designed to enhance selective adsorption towards VOCs under humid conditions via confined growth strategy. Ti-clusters were first anchored into pores of ordered mesoporous carbon (OMC), and then confined grown into NH 2 -MIL(Ti)-125 via 'ship-in-the-bottle' approach. Hydrophobic shell of OMC concurrently protected the adsorption sites on NH 2 -MIL(Ti)-125 from H 2 O occupation and enhanced affinity towards non-polar toluene. Moreover, the resulting composited supplied abundant diffusion channels for toluene thereby accelerated the mass transfer though mesopores (OMC) and micropores (MOFs). As expected, the hydrophobic-shell NH 2 -MIL(Ti)-125@OMC composite efficiently enhanced hydrophobic property and toluene adsorption affinity. It obtained a dramatical increase in toluene adsorption capacity (3.86 mmol/g at 0.001 P / P 0) about 7.4 times of NH 2 -MIL(Ti)-125, and a 29% decrease in water vapor adsorption capacity (0.30 g/g at 1 mbar), which much superior than many reported expensive adsorbents. In addition, the composite induced more confined micropores to mesopores interconnected structure in MIL(Ti)@OMC Ti , and hence facilitated toluene diffusion. The toluene rate constant of pseudo-second-order adsorption (k a) on the MIL(Ti)@OMC Ti was up to 0.12 g/(mmol∙min), which was 1.2–2.0 times higher than those of the MIL(Ti) species. Moreover, breakthrough curve indicated that MIL(Ti)@OMC Ti showed 1.5 times of toluene working capacity with faster diffusivity at 80% RH compared to pure NH 2 -MIL(Ti)-125, while the latter exhibited much lower value of Q w / Q e than that of the former. This work provides a novel composite strategy for hydrophobic MOFs construction, and deeper understanding for VOCs/H 2 O competitive adsorption on MOFs composites in large scale applications. [ABSTRACT FROM AUTHOR]

• NSAIDs construct imprinted pores in UiO-66s for enhancement adsorption of DCF. • NSAIDs imprinted UiO-66s exhibit larger pores and unique surface property. • Adsorbed DCF/Cu(II) act as new bridging sites for UiO-66@NAP to adsorb more DCF/Cu(II). • DCF shows stronger promotion effect of UiO-66@NAP for Cu(II) adsorption in binary system. • UiO-66@NAP shows high adsorbed uptakes for DCF/Cu(II) with 573/135 mg/g in binary system. [Display omitted] Competitive adsorption of complex nonsteroidal anti-inflammatory drugs (NSAIDs) from wastewater often reduces the adsorption capacity of object pollutants on most porous materials. To address this issue, NSAIDs molecules were proposed for engineering imprinted pores in UiO-66s to boost their adsorption capacity towards diclofenac sodium (DCF) and Cu(II) in a complex solution. Naproxen (NAP) with proper chemical structure was proved to introduce more imprinted pores (at ~19 Å) with enhanced mesoporous volume, abundant unsaturated metal sites, and terminal hydroxyl groups in UiO-66@NAP. These new intriguing properties awarded high adsorption affinity to UiO-66@NAP for DCF and Cu(II), and their adsorption capacities reached up to 385 and 52 mg/g for single DCF and Cu(II) components, respectively. When DCF and Cu(II) simultaneously appeared in an aqueous solution, DCF was proved to preferentially occupy adsorption sites on UiO-66@NAP with higher adsorption kinetics compared to Cu(II). Afterwards, these pre-adsorbed DCF acted as new adsorption sites to bridge more Cu(II) in the solution. Similarly, the adsorbed Cu(II) on UiO-66@NAP had the same reciprocal bridging effect towards DCF, which realized the synergistic adsorption of DCF and Cu(II) over UiO-66@NAP. Notably, DCF was found to greatly boost the synergistic effect of the Cu(II) adsorption. As a result, UiO-66@NAP exhibited 1.5 and 2.6 times higher uptakes for DCF (573 mg/g) and Cu(II) (135 mg/g) in the binary system compared to their single pollutant system, and its equilibrium adsorption capacity was much higher compared to several state-of-the-art adsorbents. The current work set out a new strategy to modify MOFs for enhanced adsorption of complex NSAID contaminants and revealed a deep understanding of the interactions between NSAIDs and heavy metals ions. [ABSTRACT FROM AUTHOR]

• Short-chains PEG is implanted into MIL-101 cage via coordination of –OH with Cr3+. • PEG is proved to form a hydrophobic barrier and raise H 2 O diffusion resistance. • Formed novel pore (11.2 Å) enhances dispersion force to toluene showing high uptake. • PEG restricts H 2 O diffusion in their implanted area but has less effect on toluene. • PEG 5 @MIL-101 shows 3.3 times of toluene working capacity than MIL-101 at 80% RH. Adsorption of volatile organic compounds (VOCs) under high humidity is crucial for metal–organic frameworks (MOFs) in practical applications. To enhance competitive adsorption of VOCs under humidity, polyethylene glycol (PEG) with hydrophobic short-chains was implanted as hydrophobic barrier into MIL-101(Cr). Characterization and simulation results showed that the terminal –OH groups of PEG chains were coordinated with the Cr sites in MIL-101(Cr) and formed a hydrophobic pore (11.2 Å) of "cage-in-cage" geometry. PEG chains significantly hindered the diffusion of water into the MOFs while allowed toluene molecules. The new hydrophobic pores of PEG 5 @MIL-101 enhanced adsorption capacity and diffusivity for toluene by 30.8% (4.68 mmol/g at 1 mbar) and 31.5% (1.88 × 10−2), while decreased adsorption capacity and diffusivity for water by 53.7% and 26.8% compared to primary MOF. Breakthrough curve showed 3.3 times of toluene working capacity on PEG 5 @MIL-101 at 80% RH compared to pristine MIL-101(Cr). [ABSTRACT FROM AUTHOR]

• pH-switchable UiO-66s were fabricated via three amino acids. • Asymmetric carboxylic coordination expanded pore size with –NH 2 surface in UiO-66. • UiO-66-Y realized 1.9 times higher adsorption uptake for SY than pristine sample. • UiO-66-Y exhibited > 10 times higher selectivity (>390) for SY/MB than pristine one. • UiO-66-Y realizes self-ad/desorption for 6 consecutive recycling via pH-switch. The pH-switchable UiO-66 were engineered via in-situ amino acids (AA) doping for the highly selective adsorption of anionic dyes (i.e. sunset yellow FCF (SY)). Three AA doped samples, i.e. UiO-66-V (valine), UiO-66-T (threonine), and UiO-66-Y (tyrosine), have fabricated hierarchical structure and endowed –NH 2 surface in framework structure concurrently. These AA doped UiO-66s awarded highly selective adsorption and fast diffusivity towards the mentioned anionic dyes. More interestingly, enriched –NH 2 groups endowed AA doped UiO-66s a significant pH-responsive character for selectivity of anionic/cationic dyes. Textural characterization and adsorption measurement confirmed that high surface areas (>1070 m2/g) with defected pores and –NH 2 surface significantly enhanced adsorption uptake (352.8 mg/g) and diffusion rate (168 × 10−3 min−1) for SY on AA doped UiO-66s, about 1.9 and 5.9 times respectively as that on pristine UiO-66. The AA doped UiO-66s exhibited one order of magnitude higher selectivity (>390) for SY against MB than that of original UiO-66. More importantly, the alteration in surface charge (–NH 2 H + ⇌ O H - -NH 3 +) endorsed a great variation in the selectivity of AA doped UiO-66s to dyes when adjusting pH from 4 to 8, showing an excellent pH on-off switchable property. Also, it realized a stable self-adsorption/desorption recycling process via pH-switching for 6 consecutive cycles. With these features, the pH-switchable defected UiO-66 realized highly efficiency adsorption and non-thermal separation/regeneration process for anionic dyes. [ABSTRACT FROM AUTHOR]