documentclass{standalone}
usepackage[utf8]{inputenc}
usepackage{graphicx}
usepackage{floatrow}
usepackage{tikz}
usepackage{pgfplots}
usepackage{fixltx2e}
usepackage{siunitx}
usepackage{lscape}
usepackage{diagbox}
usepackage{caption}
usepackage{xcolor}
usepackage[version=4]{mhchem}
usepackage{subcaption}
usepgfplotslibrary{groupplots}
DeclareSIUnit{molar}{M}
pgfplotsset{compat=newest}



begin{document}

begin{figure}[h]
setlength{abovecaptionskip}{15pt plus 3pt minus 2pt}
begin{minipage}{columnwidth}
centering
begin{tikzpicture}[scale = .65, transform shape,trim left]
begin{groupplot}[
group style={
group size=2 by 3,
horizontal sep=0pt,
vertical sep=50pt
},
    scale only axis,
    xlabel={nm},
    ylabel={Abs},
    xmin=385, xmax=565,
    xtick pos=left,
    ytick pos=left,
    no marks,
    max space between ticks=1000pt,
    try min ticks=4,
    xlabel={},
    ylabel={}
]

nextgroupplot[title=textbf{(a)} $15:60$ (TPPStextsubscript{4}-ce{2Cl}:Lig{1})]
addplot  table [col sep=comma, x=nm, y=10] {ST053 1560 Por SG.csv};label{1560porsg1}
addplot  table [col sep=comma, x=nm, y=100] {ST053 1560 Por SG.csv};label{1560porsg2}
addplot  table [col sep=comma, x=nm, y=200] {ST053 1560 Por SG.csv};label{1560porsg3}

nextgroupplot[title=textbf{(e)} $60:15$ (TPPStextsubscript{4}-ce{2Cl}:Lig{1})]
addplot  table [col sep=comma, x=nm, y=10] {ST053 6015 Por SG.csv};
addplot  table [col sep=comma, x=nm, y=100] {ST053 6015 Por SG.csv};
addplot  table [col sep=comma, x=nm, y=200] {ST053 6015 Por SG.csv};

nextgroupplot[title=textbf{(g)} $60:15$ (TPPStextsubscript{4}-ce{2Cl}:Buffer)]
addplot table [col sep=comma, x=nm, y=10] {ST053 6015 Por blank SG.csv};
addplot table [col sep=comma, x=nm, y=100] {ST053 6015 Por blank SG.csv};
addplot table [col sep=comma, x=nm, y=200] {ST053 6015 Por blank SG.csv};

end{groupplot}
node at ($(group c1r2.west)!0.5!(group c1r2.west)$)[xshift=-1.5cm]{rotatebox{90}{large{Absorption}}};
node at ($(group c1r3.south)!0.5!(group c2r3.south)$)[yshift=-1.5cm]{large{Nanometer}};
end{tikzpicture}
end{minipage}
caption{Caption}
end{figure}

end{document}