The cost-effectiveness of osteoporosis medications for preventing periprosthetic fractures following femoral neck fracture indicated hip arthroplasty: a break-even analysis.

Osteoporosis treatment following arthroplasty for femoral neck fracture (FNF) is associated with lower rates of periprosthetic fracture (PPF). Our study evaluated the economic viability of treatment in patients following arthroplasty and demonstrates that treatment with oral bisphosphonates can be cost-effective in preventing PPF. INTRODUCTION: Osteoporosis treatment following arthroplasty for femoral neck fracture (FNF) is associated with lower rates of periprosthetic fracture (PPF). Although cost-effective in reducing the rate of secondary fragility fracture, the economic viability of osteoporosis treatment in preventing PPF has not been evaluated. Therefore, the purpose of this study is to use a break-even analysis to determine whether and which current osteoporosis medications are cost-effective in preventing PPF following arthroplasty for FNFs. METHODS: Three-year average cost of osteoporosis medication (oral bisphosphonates, estrogen hormonal therapy, intravenous (IV) bisphosphonates, denosumab, teriparatide, and abaloparatide), costs of PPF care, and PPF rates in patients who underwent hip arthroplasty for FNFs without osteoporosis treatment were used to perform a break-even analysis. The absolute risk reduction (ARR) related to osteoporosis treatment and sensitivity analyses were used to evaluate the cost-effectiveness of this intervention and break-even PPF rates. RESULTS: Oral bisphosphonate therapy following arthroplasty for hip fractures would be economically justified if it prevents one out of 56 PPFs (ARR, 1.8%). Given the current cost and incidence of PPF, overall treatment can only be economically viable for PPF prophylaxis if the 3-year costs of these agents are less than $1500. CONCLUSION: The utilization of lower cost osteoporosis medications such as oral bisphosphonates and estrogen hormonal therapy as PPF prophylaxis in this patient population would be economically viable if they reduce the PPF rate by 1.8% and 1.5%, respectively. For IV bisphosphonates and newer agents to be economically viable as PPF prophylaxis in the USA, their costs need to be significantly reduced.

Correlation between research productivity during and after orthopaedic surgery training.

Background: Research experience is mandatory for all Orthopaedic Surgery residency programs. Although the allocation of required protected time and resources varies from program to program, the underlying importance of research remains consistent with mutual benefit to both residents and the program and faculty. Authorship and publications have become the standard metric used to evaluate academic success. This study aimed to determine if there is a correlation between the research productivity of Orthopaedic Surgery trainees and their subsequent research productivity as attending Orthopaedic Surgeons. Methods: Using the University of Mississippi Orthopaedic Residency Program Research Productivity Rank List, 30 different Orthopaedic Surgery Residency Programs were analyzed for the names of every graduating surgeon in their 2013 class. PubMed Central was used to screen all 156 physicians and collect all publications produced by them between 2008 and August 2022. Results were separated into two categories: Publications during training and Publications post-training. Results: As defined above, 156 Surgeons were analyzed for publications during training and post-training. The mean number of publications was 7.02 ± 17.819 post-training vs. 2.47 ± 4.313 during training, P < 0.001. The range of publication post-training was 0-124 vs. 0-30 during training. Pearson correlation between the two groups resulted in a value of 0.654, P < 0.001. Conclusion: Higher research productivity while training correlates to higher productivity post-training, but overall Orthopaedic surgeons produce more research after training than during. With the growing importance of research, more mentorship, time, and resources must be dedicated to research to instill and foster greater participation while in training.

Comparison of rerupture rates after operative and nonoperative management of Achilles tendon rupture in older populations: Systematic review and meta-analysis.

Background: This systematic review and meta-analysis investigated the treatment for Achilles tendon rupture (ATR) associated with the lowest risk of rerupture in older patients. Methods: Five databases were searched through September 2022 for studies published in the past 10 years analyzing operative and nonoperative ATR treatment. Studies were categorized as "nonelderly" if they reported only on patients aged 18-60 years. Studies that included at least 1 patient older than age 70 were categorized as "elderly inclusive." Of 212 studies identified, 28 were eligible for inclusion. Of 2965 patients, 1165 were treated operatively: 429 (37%) from elderly-inclusive studies and 736 (63%) from nonelderly studies. Of the 1800 nonoperative patients 553 (31%) were from nonelderly studies and 1247 (69%) were from elderly-inclusive studies. Results: For nonoperative treatment, the rate of rerupture was higher in nonelderly studies (83/1000 cases, 95% CI = 58, 113) than in elderly-inclusive studies (38/1000 cases, 95% CI = 22, 58; P<.001). For operative treatment no difference was found in the rate of rerupture between nonelderly studies (7/1000 cases, 95% CI = 0, 21) and elderly-inclusive studies (12/1000 cases, 95% CI = 0, 35; P<.78). Overall, operative treatment was associated with a rerupture rate of 1.5% (95% CI: 1.0%, 2.8%) (P<.001), which was lower than the 5% rate reported by other studies for nonoperative management (P<.001). Conclusion: Older patients may benefit more than younger patients from nonoperative treatment of ATR. More studies are needed to determine the age at which rerupture rates decrease among nonoperatively treated patients. Level of Evidence: 3.

Open Reduction Internal Fixation vs Primary Arthrodesis for Lisfranc Fracture-Dislocations: A Cost Analysis.

Background: Lisfranc fracture-dislocation is an uncommon but serious injury that currently lacks universal consensus on optimal operative treatment. Two common fixation methods are open reduction and internal fixation (ORIF) and primary arthrodesis (PA). The objective of this study is to analyze the cost difference between ORIF and PA of Lisfranc injuries, along with the contribution of medical services to overall costs. Methods: This was a retrospective cost analysis of the MarketScan database from 2010 to 2020. MarketScan is an insurance and commercial claims database that integrates deidentified patient information. It captures person-specific clinical utilization, expenditures, and enrollment across inpatient and outpatient services. Patients undergoing primary ORIF (CPT code 28615) vs PA (28730 and 28740) for Lisfranc fracture-dislocation were identified. The primary independent variable was ORIF vs PA of Lisfranc injury. Total costs due to operative management was the primary objective. The utilization of and costs contributed by medical services was a secondary outcome. Results: From 2010 to 2020, a total of 7268 patients underwent operative management of Lisfranc injuries, with 5689 (78.3%) ORIF and 1579 (21.7%) PA. PA was independently associated with increased net and total payment and coinsurance, clinic visits, and imaging, and patients attended significantly more PT sessions. Conclusion: Using this large database that does not characterize severity or extent of injury, we found that treatment of Lisfranc fracture-dislocation with ORIF was associated with substantially lower initial episode of treatment costs compared with PA. Specific excessive cost drivers for PA were clinic visits, PT sessions, and imaging. Level of Evidence: Level III, retrospective cohort study.

Perceptions of Racial and Gender Microaggressions in an Academic Orthopaedic Department.

Orthopaedic surgery consistently ranks last among all medical specialties in diversity and inclusion. While active efforts have recently been implemented to enact change, no study to date has explored the potential effects that social microaggressions have on an individual's career in orthopaedic surgery. The primary aim of this study was to investigate the influence of the perceived experiences of gender and race-based microaggressions on orthopaedic surgery residents, fellows, and attendings in their decision to pursue a career in orthopaedic surgery. Methods: A 34-question institutional review board-approved, modified version of the validated Racial and Ethnic Minorities Scale and Daily Life Experiences survey was sent to a total of 84 individuals at the University of Miami (UM) Department of Orthopaedics. Responses were anonymously collected from current UM orthopaedic residents, fellows, and attendings. Survey results were analyzed for the prevalence of microaggressions in the context of sex, race, ethnicity, academic goals, daily scenarios, and department support. p-Values less than 0.05 were considered statistically significant. Results: Fifty-four of 84 respondents (64%) completed the survey. Female respondents experienced significantly more gender-based microaggressions than male respondents. On average, male participants disagreed that their experiences with microaggressions made them doubt their ability to pursue a career in orthopaedic surgery while female participants responded they were neutral. In comparison with their White counterparts, non-White and Hispanic ethnicity participants demonstrated a statistically significantly greater frequency of race and ethnicity-based microaggressions. Conclusion: Our study demonstrates that female participants, non-White participants, and Hispanic minorities across all levels of training experience a higher frequency of microaggressions. The impact of these experiences on career decisions and goals for women and persons of color in orthopaedic surgery at this single institution is mixed. Experienced microaggressions should be further investigated as a potential barrier to recruitment and retention of under-represented minorities in orthopaedic surgery. Level of Evidence: III.

Trends in Racial, Ethnic, and Gender Diversity in Orthopaedic Surgery Adult Reconstruction Fellowships From 2007 to 2021.

BACKGROUND: Orthopaedic surgery has seen improvement in its representation of women, whereas the representation of racial/ethnic minorities has remained stagnant over the past decade. Overall, the surgical field lags behind other specialties in sex and racial/ethnic parity. Although demographic disparities within orthopaedics have been analyzed for both residents and faculty members, information for adult reconstruction fellows remains limited. METHODS: Sex and race/ethnicity demographics for adult reconstruction orthopaedic fellowship matriculants were collected via a database published by the Accreditation Council for Graduate Medical Education (ACGME) from 2007 to 2021. Statistical analyses, including descriptive statistics and significance testing, were performed. RESULTS: During the 14-year time frame, men trainees remained high with an overall average percentage of 88% and demonstrated increasing representation (P trend = .012). White non-Hispanics, Asians, Blacks, and Hispanics represented on average 54%, 11%, 3%, and 4%, respectively. White non-Hispanics (P trend = .039) and Asians (P trend = .030) saw increasing and decreasing representation, respectively. Women, Blacks, and Hispanics remained relatively stagnant throughout the observation period as no trends were appreciable (P trend >.05, each). CONCLUSION: Using publicly available demographic data from the Accreditation Council for Graduate Medical Education (ACGME) from 2007 to 2021, we found relatively limited progress in the representation of women and those from traditionally marginalized groups seeking additional training in adult reconstruction. Our findings mark an initial step in measuring the demographic diversity among adult reconstruction fellows. Further research is needed to ascertain specific factors likely to attract and retain members from minoritized groups into orthopaedics.

Trends in Racial, Ethnic, and Gender Diversity Among Hand Surgery Fellows From 2007 to 2021.

PURPOSE: There is a paucity of research on the demographic trends of orthopedic and plastic hand surgery fellows. The purpose of this study was to ascertain the current state of racial and gender demographic trends in hand surgery fellowship from 2007 to 2021. METHODS: We analyzed fellowship demographic data from the Accreditation Council for Graduate Medical Education public database from 2007-2008 through 2020-2021. The gender of hand surgery fellows was categorized as male, female, or not reported and their race/ethnicity as White, Non-Hispanic; Asian or Pacific Islander, Hispanic; Black, Non-Hispanic; American Indian or Alaskan Native; other; or unknown. We extracted the number of fellows per year for each category and calculated the percentage equivalents and average percentages. We performed the chi-square test for trend (Cochran-Armitage test) to identify any significant changes in the percentages of gender and race/ethnicity between 2007 and 2021. RESULTS: There was a significant increase in the percentage of hand surgery fellows who are women (20.7% to 30.7%) and Asian or Pacific Islander (13.3% to 25.3%). There was no significant change in the percentage of Hispanic or Black, Non-Hispanic fellows. CONCLUSIONS: Although there have been some increases, hand surgery fellows continue to be underrepresented by women and minorities, consistent with the demographic of orthopedic and plastic surgery residents. There have been increasing trends in the number of women and minorities in medical schools, which leaves room for improvement from the downstream prospective applicant pool. CLINICAL RELEVANCE: The physician-patient relationship can potentially be strengthened by race and gender concordance; however, many minority and female hand surgery patients do not have physicians who are women or of the same ethnic background. Patient satisfaction, trust, and potential health outcomes may be improved with a physician workforce that reflects the diversity of their patients.

Operative vs Nonoperative Management of Achilles Tendon Rupture: A Cost Analysis.

Background: Achilles tendon rupture (ATR) is a common injury with a growing incidence rate. Treatment is either operative or nonoperative. However, evidence is lacking on the cost comparison between these modalities. The objective of this study is to investigate the cost differences between operative and nonoperative treatment of ATR using a large national database. Methods: Patients who received treatment for an ATR were abstracted from the large national commercial insurance claims database, Marketscan Commercial Claims and Encounters Database (n = 100 825) and divided into nonoperative (n = 75 731) and operative (n = 25 094) cohorts. Demographics, location, and health care charges were compared using multivariable regression analysis. Subanalysis of costs for medical services including clinic visits, imaging studies, opioid usage, and physical therapy were conducted. Patients who underwent secondary repair were excluded. Results: Operative treatment was associated with increased net and total payments, coinsurance, copayment, deductible, coordination of benefits (COB) / savings, greater number of clinic visits, radiographs, magnetic resonance imaging (MRI) scans, and physical therapy (PT) sessions, and with higher net costs due to clinic visits, radiographs, MRIs, and PT (P < .001). Operative repair at an ambulatory surgical center was associated with a lower net and total payment, and a significantly higher deductible compared to in-hospital settings (P < .001). Both cohorts received similar numbers of opioid prescriptions during the study period. Yet, operative patients had a significantly shorter duration of opioid use. After controlling for confounders, operative repair was also independently associated with lower net costs due to opioid prescriptions. Conclusion: Compared with nonoperatively managed ATR, surgical repair is associated with greater costs partially because of greater utilization of clinic visits, imaging, and physical therapy sessions. However, surgical costs may be reduced when procedures are performed in ambulatory surgery centers vs hospital facilities. Nonoperative treatment is associated with higher prescription costs secondary to longer duration of opioid use. Level of Evidence: Level III, retrospective cohort study.

Trends in Racial, Ethnic, and Gender Diversity in Orthopedic Surgery Spine Fellowships From 2007 to 2021.

STUDY DESIGN: Descriptive. OBJECTIVE: The objective of this study is to analyze trends in racial, ethnic, and gender diversity in orthopedic spine surgery fellowship trainees. SUMMARY OF BACKGROUND DATA: Orthopedic surgery has consistently been labeled as one of the least diverse fields in Medicine. Although some effort has been made to combat this in recent years at the residency level, it is uncertain whether spine fellowships have had any changes in fellow demographics. MATERIALS AND METHODS: Fellowship demographic data were collected through the Accreditation Council for Graduate Medical Education. Data collected included gender (male, female, and not reported) and race (White, Asian, Black, Hispanic, Native Hawaiians, American Indian or Alaskan Native, other, and unknown). Percentage equivalents were calculated for each group from 2007 to 2008 to 2020 to 2021. A χ 2 test for trend (Cochran-Armitage test) was done to determine whether there was a significant change in percentages of each race and gender during the study period. The results were considered statistically significant at P <0.05. RESULTS: White, Non-Hispanic males represent the largest proportion of orthopedic spine fellowship positions each year. From 2007 to 2021, there were no significant changes in the representation of any race or gender of orthopedic spine fellows. Males ranged from 81% to 95%, Whites from 28% to 66%, Asians from 9% to 28%, Blacks from 3% to 16%, and Hispanics from 0% to 10%. Native Hawaiians and American Indians remained at 0% for all years included in the study. Females and all races, excluding Whites, continue to be under-represented in orthopedic spine fellowship. CONCLUSIONS: Orthopedic spine surgery fellowship programs have not made substantial progress in diversifying its population. More attention is needed to increase diversity in residency programs through pipeline programs, increased mentorship and sponsorship, and early exposure to the field. LEVEL OF EVIDENCE: 1.

Effect of Faculty Diversity on Minority Student Populations Matching into Orthopaedic Surgery Residency Programs.

Greater faculty diversity within orthopaedic residency programs has been associated with an increased application rate from students of similarly diverse demographic backgrounds. It is unknown whether these underrepresented student populations have an equitable likelihood of being highly ranked and matching at these programs. Thus, we sought to evaluate the relationship between faculty and resident diversity, with a specific focus on sex, racial/ethnic groups that are underrepresented in medicine (URiM), and international medical graduates (IMGs). Methods: The American Orthopaedic Association's Orthopaedic Residency Information Network database was used to collect demographic data on 172 US residency programs. Linear regression analyses were performed to determine the relationship between the proportion of female or URiM attendings at a program and the proportion of female, URiM, or IMG residents or top-ranked applicants (≥25 rank). URiM was defined as "racial and ethnic populations that are underrepresented in the medical profession relative to their numbers in the general population." Results: A mean of 13.55% of attendings were female and 14.14% were URiM. A larger fraction of female attendings was a positive predictor of female residents (p < 0.001). Similarly, a larger percentage of URiM attendings was a positive predictor of URiM residents (p < 0.001), as well as of URiM (p < 0.001) and IMG (p < 0.01) students being ranked highly. There was no significant association between URiM attendings and female residents/overall top-ranked applicants, or vice versa. Conclusions: Residency programs with more female attendings were more likely to match female residents, and programs with more URiM attendings were more likely to highly rank URiM and IMG applicants as well as match URiM residents. Our findings indicate that orthopaedic surgery residencies may be more likely to rank and match female or URiM students at similar proportions to that of their faculty. This may reflect minority students preferentially applying to programs with more diverse faculty because they feel a better sense of fit and are likely to benefit from a stronger support system. Level of Evidence: III.

Use of Commercially Produced Medical Education Videos in a Cardiovascular Curriculum: Multiple Cohort Study.

BACKGROUND: Short instructional videos can make learning more efficient through the application of multimedia principles, and video animations can illustrate the complex concepts and dynamic processes that are common in health sciences education. Commercially produced videos are commonly used by medical students but are rarely integrated into curricula. OBJECTIVE: Our goal was to examine student engagement with medical education videos incorporated into a preclinical Cardiovascular Systems course. METHODS: Students who took the first-year 8-week Cardiovascular Systems course in 2019 and 2020 were included in the study. Videos from Osmosis were recommended to be watched before live sessions throughout the course. Video use was monitored through dashboards, and course credit was given for watching videos. All students were emailed electronic surveys after the final exam asking about the course's blended learning experience and use of videos. Osmosis usage data for number of video views, multiple choice questions, and flashcards were extracted from Osmosis dashboards. RESULTS: Overall, 232/359 (64.6%) students completed surveys, with rates by class of 81/154 (52.6%) for MD Class of 2022, 39/50 (78%) for MD/MPH Class of 2022, and 112/155 (72.3%) for MD Class of 2023. Osmosis dashboard data were available for all 359 students. All students received the full credit offered for Osmosis engagement, and learning analytics demonstrated regular usage of videos and other digital platform features. Survey responses indicated that most students found Osmosis videos to be helpful for learning (204/232, 87.9%; P=.001) and preferred Osmosis videos to the traditional lecture format (134/232, 57.8%; P<.001). CONCLUSIONS: Commercial medical education videos may enhance curriculum with low faculty effort and improve students' learning experiences. Findings from our experience at one medical school can guide the effective use of supplemental digital resources for learning, and related evaluation and research.

Infrapatellar Fat Pad/Synovium Complex in Early-Stage Knee Osteoarthritis: Potential New Target and Source of Therapeutic Mesenchymal Stem/Stromal Cells.

The infrapatellar fat pad (IFP) has until recently been viewed as a densely vascular and innervated intracapsular/extrasynovial tissue with biomechanical roles in the anterior compartment of the knee. Over the last decade, secondary to the proposition that the IFP and synovium function as a single unit, its recognized tight molecular crosstalk with emerging roles in the pathophysiology of joint disease, and the characterization of immune-related resident cells with varying phenotypes (e.g., pro and anti-inflammatory macrophages), this structural complex has gained increasing attention as a potential therapeutic target in patients with various knee pathologies including osteoarthritis (KOA). Furthermore, the description of the presence of mesenchymal stem/stromal cells (MSC) as perivascular cells within the IFP (IFP-MSC), exhibiting immunomodulatory, anti-fibrotic and neutralizing activities over key local mediators, has promoted the IFP as an alternative source of MSC for cell-based therapy protocols. These complementary concepts have supported the growing notion of immune and inflammatory events participating in the pathogenesis of KOA, with the IFP/synovium complex engaging not only in amplifying local pathological responses, but also as a reservoir of potential therapeutic cell-based products. Consequently, the aim of this review is to outline the latest discoveries related with the IFP/synovium complex as both an active participant during KOA initiation and progression thus emerging as a potential target, and a source of therapeutic IFP-MSCs. Finally, we discuss how these notions may help the design of novel treatments for KOA through modulation of local cellular and molecular cascades that ultimately lead to joint destruction.

Spatial alignment of 3D printed scaffolds modulates genotypic expression in pre-osteoblasts.

3D printing, an advent from rapid prototyping technology is emerging as a suitable solution for various regenerative engineering applications. In this study, blended gelatin-sodium alginate 3D printed scaffolds with different pore geometries were developed by altering the spatiotemporal alignment of even layered struts in the scaffolds. A significant difference in compression modulus and osteogenic expression due to the difference in spatiotemporal printing was demonstrated. Pore geometry was found to be more dominant than the compressive modulus of the scaffold in regulating osteogenic gene expression. A shift in pore geometry by at least 45° was critical for significant increase in osteogenic gene expression in MC3T3-E1 cells.

Development of Tripolymeric Triaxial Electrospun Fibrous Matrices for Dual Drug Delivery Applications.

Since the first work by Laurencin and colleagues on the development of polymeric electrospinning for biomedical purposes, the use of electrospinning technology has found broad applications in such areas of tissue regeneration and drug delivery. More recently, coaxial electrospinning has emerged as an important technique to develop scaffolds for regenerative engineering incorporated with drug(s). However, the addition of a softer core layer leads to a reduction in mechanical properties. Here, novel robust tripolymeric triaxially electrospun fibrous scaffolds were developed with a polycaprolactone (PCL) (core layer), a 50:50 poly (lactic-co-glycolic acid) (PLGA) (sheath layer) and a gelatin (intermediate layer) with a dual drug delivery capability was developed through modified electrospinning. A sharp increase in elastic modulus after the incorporation of PCL in the core of the triaxial fibers in comparison with uniaxial PLGA (50:50) and coaxial PLGA (50:50) (sheath)-gelatin (core) fibers was observed. Thermal analysis of the fibrous scaffolds revealed an interaction between the core-intermediate and sheath-intermediate layers of the triaxial fibers contributing to the higher tensile modulus. A simultaneous dual release of model small molecule Rhodamine B (RhB) and model protein Fluorescein isothiocynate (FITC) Bovine Serum Albumin (BSA) conjugate incorporated in the sheath and intermediate layers of triaxial fibers was achieved. The tripolymeric, triaxial electrospun systems were seen to be ideal for the support of mesenchymal stem cell growth, as shrinkage of fibers normally found with conventional electrospun systems was minimized. These tripolymeric triaxial electrospun fibers that are biomechanically competent, biocompatible, and capable of dual drug release are designed for regenerative engineering and drug delivery applications.

HIV/AIDS and the African-American Community 2018: a Decade Call to Action.

HIV/AIDS disproportionately affects African-Americans more than any other racial or ethnic group in the USA. Currently representing only 12% of the US population, African-Americans now comprise close to half of the total reported HIV/AIDS cases in the USA according to the Centers for Disease Control and Prevention since the initial reporting of HIV/AIDS. In this paper, we examined the prevalence and current direction of the HIV/AIDS epidemic in the African-American community especially in comparison to our first call to action in 2008. The situation remains dire and broader attention is necessary from the public health and medical sectors who serve the majority of African-American populations and the community at-large to work towards closing this health disparity gap. This paper thus recommends an action plan for community leaders (i.e., the public health sector, policy makers, public health practitioners, and other stakeholders) to reduce the disparity.

Monolith-Supported Amine-Functionalized Mg2(dobpdc) Adsorbents for CO2 Capture.

The potential of using an amine-functionalized metal organic framework (MOF), mmen-M2(dobpdc) (M = Mg and Mn), supported on a structured monolith contactor for CO2 capture from simulated flue gas is explored. The stability of the unsupported MOF powders under humid conditions is explored using nitrogen physisorption and X-ray diffraction analysis before and after exposure to humidity. Based on its superior stability to humidity, mmen-Mg2(dobpdc) is selected for further growth on a honeycomb cordierite monolith that is wash-coated with α-alumina. A simple approach for the synthesis of an Mg2(dobpdc) MOF film using MgO nanoparticles as the metal precursor is used. Rapid drying of MgO on the monolith surface followed by a hydrothermal treatment is demonstrated to allow for the synthesis of a MOF film with good crystallite density and favorable orientation of the MOF crystals. The CO2 adsorption behavior of the monolith-supported mmen-Mg2(dobpdc) material is assessed using 10% CO2 in helium and 100% CO2, demonstrating a CO2 uptake of 2.37 and 2.88 mmol/g, respectively. Excellent cyclic adsorption/desorption performance over multiple cycles is also observed. This is one of the first examples of the deployment of an advanced MOF adsorbent in a scalable, low-pressure drop gas-solid contactor. Such demonstrations are critical to the practical application of MOF materials in adsorptive gas separations, as structured contactors have many practical advantages over packed or fluidized beds.

Boron Trifluoride Gas Adsorption in Metal-Organic Frameworks.

Coordinatively unsaturated metal-organic frameworks (MOFs) were studied for boron trifluoride (BF3) sorption. MOF-74-Mg, MOF-74-Mn, and MOF-74-Co show high initial uptake (below 6.7 × 10-3 bar) with negligible deliverable capacity. The BF3 isotherm of MOF-74-Cu exhibits gradual uptake up to 0.9 bar and has a deliverable gravimetric capacity that is more than 100% higher than activated carbon. Two other Cu2+ MOFs, MOF-505 and HKUST-1, have slightly lower deliverable capacities compared to MOF-74-Cu.

Direct Capture of CO2 from Ambient Air.

The increase in the global atmospheric CO2 concentration resulting from over a century of combustion of fossil fuels has been associated with significant global climate change. With the global population increase driving continued increases in fossil fuel use, humanity's primary reliance on fossil energy for the next several decades is assured. Traditional modes of carbon capture such as precombustion and postcombustion CO2 capture from large point sources can help slow the rate of increase of the atmospheric CO2 concentration, but only the direct removal of CO2 from the air, or "direct air capture" (DAC), can actually reduce the global atmospheric CO2 concentration. The past decade has seen a steep rise in the use of chemical sorbents that are cycled through sorption and desorption cycles for CO2 removal from ultradilute gases such as air. This Review provides a historical overview of the field of DAC, along with an exhaustive description of the use of chemical sorbents targeted at this application. Solvents and solid sorbents that interact strongly with CO2 are described, including basic solvents, supported amine and ammonium materials, and metal-organic frameworks (MOFs), as the primary classes of chemical sorbents. Hypothetical processes for the deployment of such sorbents are discussed, as well as the limited array of technoeconomic analyses published on DAC. Overall, it is concluded that there are many new materials that could play a role in emerging DAC technologies. However, these materials need to be further investigated and developed with a practical sorbent-air contacting process in mind if society is to make rapid progress in deploying DAC as a means of mitigating climate change.

Isostructural synthesis of porous metal-organic nanotubes.

Employment of semirigid double-hinged di-1,2,4-triazoles has led to the synthesis of an isostructural series of metal-organic nanotubes (MONTs). The ditriazole ligands adopt a syn conformation between rigid metal chains while an appropriate anion choice provides a "capping" of the metal ions, leading to MONT formation. This approach of utilizing a variety of both semirigid ligands and metals is the first general methodology to prepare this class of 1D nanomaterial. The local geometry at the metal center depends on the metal ion employed, with Cu(I) centers adopting a tetrahedral geometry, Ag(I) centers adopting a seesaw geometry, and Cu(II) centers adopting a square-pyramidal geometry upon MONT synthesis. The pore size of the MONTs is adjusted by changing the central portion of the double-hinged ligand, allowing for a predictable method to control the pore width of the MONT. The adsorption properties of MONTs as a function of pore size revealed selective uptake of CO2 and CH4, with copper MONTs exhibiting the highest uptake. In the case of the silver MONTs, an increase in pore width improves both gas uptake and selectivity.

Rotating phenyl rings as a guest-dependent switch in two-dimensional metal-organic frameworks.

A semirigid bis(1,2,4-triazole) ligand binds in a syn conformation between copper(I) chains to form a series of two-dimensional metal-organic frameworks that display a topology of fused one-dimensional metal-organic nanotubes. These anisotropic frameworks undergo two different transformations in the solid state as a function of solvation. The 2D sheet layers can expand or contract, or, more remarkably, the phenyl rings can rotate between two distinct positions. Rotation of the phenyl rings allows for the adjustment of the tube size, depending on the guest molecules present. This "gate" effect along the 1D tubes has been characterized through single-crystal X-ray diffraction. The transformations can also be followed by powder X-ray diffraction (PXRD) and solid-state (13)C cross-polarization magic-angle-spinning (CP-MAS) NMR. Whereas PXRD cannot differentiate between transformations, solid-state (13)C CP-MAS NMR can be employed to directly monitor phenyl rotation as a function of solvation, suggesting that this spectroscopic method is a powerful approach for monitoring breathing in this novel class of frameworks. Finally, simulations show that rotation of the phenyl ring from a parallel orientation to a perpendicular orientation occurs at the cost of framework-framework energy and that this energetic cost is offset by stronger framework-solvent interactions.