Stable Metal–Organic Frameworks with Group 4 Metals: Current Status and Trends

Abstract

Group 4 metal-based metal–organic frameworks (MIV-MOFs), including Ti-, Zr-, and Hf-based MOFs, are one of the most attractive classes of MOF materials owing to their superior chemical stability and structural tunability. Despite being a relatively new field, MIV-MOFs have attracted significant research attention in the past few years, leading to exciting advances in syntheses and applications. In this outlook, we start with a brief overview of the history and current status of MIV-MOFs, emphasizing the challenges encountered in their syntheses. The unique properties of MIV-MOFs are discussed, including their high chemical stability and strong tolerance toward defects. Particular emphasis is placed on defect engineering in Zr-MOFs which offers additional routes to tailor their functions. Photocatalysis of MIV-MOF is introduced as a representative example of their emerging applications. Finally, we conclude with the perspective of new opportunities in synthesis and defect engineering.

Pore‐Surface Engineering by Decorating Metal‐Oxo Nodes with Phenylsilane to Give Versatile Super‐Hydrophobic Metal–Organic Frameworks (MOFs)

“…[26][27][28][29][30][31] In addition, the intrinsic presence of metal-OH groups at metal-oxo nodes of MOFs enables af acile and direct decoration process, [30,32] offering advantages over the ligand modification process that requires extra functional groups as "tags" for post modification steps.Herein we initiated an attempt to prepare super-hydrophobic MOFs by modification of the metal-oxo nodes.N H 2functionalized MOFs have attracted interest owing to their unique properties distinguished from the bare MOFs.N H 2 -UiO-66(Zr) represents one of the most appealing MOFs showing great potential in different applications and was thus selected. [28,31,[33][34][35][36] Phenylsilane (PhSiH 3 )was grafted onto the Zr-O metal-oxo nodes of NH 2 -UiO-66(Zr) by allowing it to react with the Zr-OH groups,e xposing the hydrophobic phenyl groups to form the super-hydrophobic NH 2 -UiO-66(Zr) (NH 2 -UiO-66(Zr)-shp) with ah igh water contact angle of 1618 8 (Scheme 1). Thet hus obtained NH 2 -UiO-66(Zr)-shp shows excellent base resistance and holds great promise in versatile applications including organic/water separation, self-cleaning, and as liquid marbles.T his work demonstrates the first attempt at preparing super-hydrophobic MOFs by modifying the metal-oxo nodes.The precise modification on the metal-oxo nodes of MOFs without blocking the windows of the pores maximizes the preservation of the inherent accessibility of the pores,e nsuring their availability in practical applications.Thus,this work advances an ovel and effective concept for designing super-hydrophobic MOFs for practical use.Scheme1.…”

∞3[Cu2(mand)2(hmt)]–MOF: A Synergetic Effect between Cu(II) and Hexamethylenetetramine in the Henry Reaction

“…The synthesized MOF is completely recyclable as demonstrated for five successive cycles.Chemistry 2020, 2 51 resemblance with enzymes, such moieties can be effective in catalysis, influencing the overall catalytic selectivity due to the steric constraints introduced by the morphology of the channels [9].However, to be used as catalysts or adsorbents, MOFs should be firstly evacuated for the adsorbed guest molecules without any collapse of the structure [10]. To achieve such stability, the literature suggested the necessity of either M +III or M +IV nodes with a high polarizing capability [11][12][13] or organic linkers with high pKa values [14]. In the case of M +II -supported MOFs, the stability may be improved by framework interpenetration [15], yet this generates a noticeable decrease in the specific surface area.…”

Pore‐Surface Engineering by Decorating Metal‐Oxo Nodes with Phenylsilane to Give Versatile Super‐Hydrophobic Metal–Organic Frameworks (MOFs)

“…[5][6][7][8][9][10][11][12][13] Recent research has involved preparing hydrophobic MOFs,n ot only to combat their failure in applications under humid conditions,b ut also endow them with improved or even novel functional properties. [28,31,[33][34][35][36] Phenylsilane (PhSiH 3 )was grafted onto the Zr-O metal-oxo nodes of NH 2 -UiO-66(Zr) by allowing it to react with the Zr-OH groups,e xposing the hydrophobic phenyl groups to form the super-hydrophobic NH 2 -UiO-66(Zr) (NH 2 -UiO-66(Zr)-shp) with ah igh water contact angle of 1618 8 (Scheme 1). [25][26][27][28] Surprisingly,t here is no attempt to design the metal-oxo nodes for functional hydrophobic MOFs,i ns pite of their easily modified nature.…”

“…[28,31,[33][34][35][36] Phenylsilane (PhSiH 3 )was grafted onto the Zr-O metal-oxo nodes of NH 2 -UiO-66(Zr) by allowing it to react with the Zr-OH groups,e xposing the hydrophobic phenyl groups to form the super-hydrophobic NH 2 -UiO-66(Zr) (NH 2 -UiO-66(Zr)-shp) with ah igh water contact angle of 1618 8 (Scheme 1). [28,31,[33][34][35][36] Phenylsilane (PhSiH 3 )was grafted onto the Zr-O metal-oxo nodes of NH 2 -UiO-66(Zr) by allowing it to react with the Zr-OH groups,e xposing the hydrophobic phenyl groups to form the super-hydrophobic NH 2 -UiO-66(Zr) (NH 2 -UiO-66(Zr)-shp) with ah igh water contact angle of 1618 8 (Scheme 1).…”