Escaping the Environmental Crises: Online Escape Rooms for Evaluating Student Data Analysis Skills.

Summative lab assessments probe student mastery over concepts, but conventional ones often result in decreased student engagement and confidence. If conventional summative lab assessments are replaced by accessible gamified evaluations, such as online escape rooms, this leads to improved student engagement and confidence. In this work, we adapted two sustainability themed online escape room activities to increase student engagement and confidence in data analyses in Integrated Chemistry I (CHEM 381) over three semesters at CSU, Chico. Over 89.7% of students earned full credit. Further, 80.0% of the written comments included positive feedback. After the online escape room assessments, 60.0% of the students rated their confidence as "high" or "very high" in all categories assessed, compared to 25.6% before the experience. Students found that the online escape room assessments were more engaging than the traditional assessment and increased their confidence as they worked toward solving two sustainability crises and competed for the quickest time to complete the escape rooms.

From n- to p-Type Material: Effect of Metal Ion on Charge Transport in Metal-Organic Materials.

An intriguing new class of two-dimensional (2D) materials based on metal-organic frameworks (MOFs) has recently been developed that displays electrical conductivity, a rarity among these nanoporous materials. The emergence of conducting MOFs raises questions about their fundamental electronic properties, but few studies exist in this regard. Here, we present an integrated theory and experimental investigation to probe the effects of metal substitution on the charge transport properties of M-HITP, where M = Ni or Pt and HITP = 2,3,6,7,10,11-hexaiminotriphenylene. The results show that the identity of the M-HITP majority charge carrier can be changed without intentional introduction of electronically active dopants. We observe that the selection of the metal ion substantially affects charge transport. Using the known structure, Ni-HITP, we synthesized a new amorphous material, a-Pt-HITP, which although amorphous is nevertheless found to be porous upon desolvation. Importantly, this new material exhibits p-type charge transport behavior, unlike Ni-HITP, which displays n-type charge transport. These results demonstrate that both p- and n-type materials can be achieved within the same MOF topology through appropriate choice of the metal ion.

Layer-by-Layer Assembled Films of Perylene Diimide- and Squaraine-Containing Metal-Organic Framework-like Materials: Solar Energy Capture and Directional Energy Transfer.

We demonstrate that thin films of metal-organic framework (MOF)-like materials, containing two perylenediimides (PDICl4, PDIOPh2) and a squaraine dye (S1), can be fabricated by layer-by-layer assembly (LbL). Interestingly, these LbL films absorb across the visible light region (400-750 nm) and facilitate directional energy transfer. Due to the high spectral overlap and oriented transition dipole moments of the donor (PDICl4 and PDIOPh2) and acceptor (S1) components, directional long-range energy transfer from the bluest to reddest absorber was successfully demonstrated in the multicomponent MOF-like films. These findings have significant implications for the development of solar energy conversion devices based on MOFs.

Liquid-Phase Epitaxially Grown Metal-Organic Framework Thin Films for Efficient Tandem Catalysis Through Site-Isolation of Catalytic Centers.

A functional metal-organic framework (MOF) composed of robust porphyrinic material (RPM) based on the pillared-paddlewheel topology is prepared with large 3 D channels, and is used to perform a tandem epoxidation/CO2 insertion reaction. The designated system benefits from two metalloporphyrins: 1) a Mn-porphyrin, which catalyzes the epoxidation of an olefin substrate, and 2) a Zn-porphyrin, which catalyzes the epoxide opening. By using an automated liquid-phase epitaxial growth system, the RPM-MOF is also prepared in layer-by-layer fashion as an ultrathin film on a self-assembled-monolayer-coated silicon platform. Deployed as a tandem catalyst, the film version yields a substantially higher catalytic turnover number for tandem methoxy-styrene epoxidation followed by CO2 insertion than the bulk crystalline MOF samples.

A porous proton-relaying metal-organic framework material that accelerates electrochemical hydrogen evolution.

The availability of efficient hydrogen evolution reaction (HER) catalysts is of high importance for solar fuel technologies aimed at reducing future carbon emissions. Even though Pt electrodes are excellent HER electrocatalysts, commercialization of large-scale hydrogen production technology requires finding an equally efficient, low-cost, earth-abundant alternative. Here, high porosity, metal-organic framework (MOF) films have been used as scaffolds for the deposition of a Ni-S electrocatalyst. Compared with an MOF-free Ni-S, the resulting hybrid materials exhibit significantly enhanced performance for HER from aqueous acid, decreasing the kinetic overpotential by more than 200 mV at a benchmark current density of 10 mA cm(-2). Although the initial aim was to improve electrocatalytic activity by greatly boosting the active area of the Ni-S catalyst, the performance enhancements instead were found to arise primarily from the ability of the proton-conductive MOF to favourably modify the immediate chemical environment of the sulfide-based catalyst.

Metal-organic framework materials for light-harvesting and energy transfer.

A critical review of the emerging field of MOFs for photon collection and subsequent energy transfer is presented. Discussed are examples involving MOFs for (a) light harvesting, using (i) MOF-quantum dots and molecular chromophores, (ii) chromophoric MOFs, and (iii) MOFs with light-harvesting properties, and (b) energy transfer, specifically via the (i) Förster energy transfer and (ii) Dexter exchange mechanism.

Post-assembly transformations of porphyrin-containing metal-organic framework (MOF) films fabricated via automated layer-by-layer coordination.

Herein, we demonstrate the robustness of layer-by-layer (LbL)-assembled, pillared-paddlewheel-type MOF films toward conversion to new or modified MOFs via solvent-assisted linker exchange (SALE) and post-assembly linker metalation. Further, we show that LbL synthesis can afford MOFs that have proven inaccessible through other de novo strategies.

Directed growth of electroactive metal-organic framework thin films using electrophoretic deposition.

Electrophoretic deposition (EPD) is used to assemble metal-organic framework (MOF) materials in nano- and micro-particulate, thin-film form. The flexibility of the method is demonstrated by the successful deposition of 4 types of MOFs: NU-1000, UiO-66, HKUST-1, and Al-MIL-53. Additionally, EPD is used to pattern the growth of NU-1000 thin films that exhibit full electrochemical activity.

Layer-by-layer fabrication of oriented porous thin films based on porphyrin-containing metal-organic frameworks.

We report the synthesis and characterization of two thin films (DA-MOF and L2-MOF) of porphyrin-based MOFs on functionalized surfaces using a layer-by-layer (LbL) approach. Profilometry measurements confirm that the film thickness increases systematically with number of growth cycles. Polarization excitation and fluorescence measurements indicate that the porphyrin units are preferentially oriented, while X-ray reflectivity scans point to periodic ordering. Ellipsometry measurements show that the films are highly porous. Since there are currently few methods capable of yielding microporous MOFs containing accessible free-base porphyrins, it is noteworthy that the LbL growth permits direct MOF incorporation of unmetalated porphyrins. Long-range energy transfer is demonstrated for both MOF films. The findings offer useful insights for subsequent fabrication of MOF-based solar energy conversion devices.

Light-harvesting and ultrafast energy migration in porphyrin-based metal-organic frameworks.

Given that energy (exciton) migration in natural photosynthesis primarily occurs in highly ordered porphyrin-like pigments (chlorophylls), equally highly ordered porphyrin-based metal-organic frameworks (MOFs) might be expected to exhibit similar behavior, thereby facilitating antenna-like light-harvesting and positioning such materials for use in solar energy conversion schemes. Herein, we report the first example of directional, long-distance energy migration within a MOF. Two MOFs, namely F-MOF and DA-MOF that are composed of two Zn(II) porphyrin struts [5,15-dipyridyl-10,20-bis(pentafluorophenyl)porphinato]zinc(II) and [5,15-bis[4-(pyridyl)ethynyl]-10,20-diphenylporphinato]zinc(II), respectively, were investigated. From fluorescence quenching experiments and theoretical calculations, we find that the photogenerated exciton migrates over a net distance of up to ~45 porphyrin struts within its lifetime in DA-MOF (but only ~3 in F-MOF), with a high anisotropy along a specific direction. The remarkably efficient exciton migration in DA-MOF is attributed to enhanced π-conjugation through the addition of two acetylene moieties in the porphyrin molecule, which leads to greater Q-band absorption intensity and much faster exciton-hopping (energy transfer between adjacent porphyrin struts). The long distance and directional energy migration in DA-MOF suggests promising applications of this compound or related compounds in solar energy conversion schemes as an efficient light-harvesting and energy-transport component.