Footnote outside theorem environment

Question

I tried to add a footnote in a tcolorbox based theorem environment, which is showing right inside the theorem box. How to position footnote at the bottom of the page?

\documentclass[a4paper]{article}

% ------------------------------------------------------------------------------------------
%                                   Packages Required
% ------------------------------------------------------------------------------------------

\usepackage{amsthm}
\usepackage{tcolorbox}

% ------------------------------------------------------------------------------------------
%                           tcolorbox and theorem Environment
% ------------------------------------------------------------------------------------------

\tcbuselibrary{theorems}
\newtcbtheorem
  []% init options
  {theorem}% name
  {Theorem}% title
  {%
    colback=green!5,
    colframe=green!35!black,
    fonttitle=\bfseries,
  }% options
  {thm}% prefix

\makeatletter
% ------------------------------------------------------------------------------------------
%                                   User defined Commands
% ------------------------------------------------------------------------------------------

\newcommand{\reals}{\mathbb{R}}
\renewcommand{\qedsymbol}{$\blacksquare$}
\newcommand{\f}[1]{$f(#1)$}
\newcommand{\tcb@cnt@theoremautorefname}{Theorem}
\makeatother

% ------------------------------------------------------------------------------------------

\begin{document}

\begin{theorem}{Cauchy's Theorem}{}
Let C be a simple\footnote{A simple curve is one which does not cross itself.}. closed curve with continously turning tangents except possibly at a finite number of of points (otherwise curve must be smooth). If \f{z} is analytic on and inside C, then 
\begin{equation}
\oint_{C} f(z) \, dz = 0
\end{equation}
\end{theorem}

\end{document}

Answer 1

You can obtain what you want with etoolbox and the footnote package (from the mdwtools bundle):

\documentclass[a4paper]{article}

% ------------------------------------------------------------------------------------------
% Packages Required
% ------------------------------------------------------------------------------------------

\usepackage{amsthm}
\usepackage{tcolorbox}
% ------------------------------------------------------------------------------------------
% tcolorbox and theorem Environment
% ------------------------------------------------------------------------------------------

\tcbuselibrary{theorems}
\newtcbtheorem
  []% init options
  {theorem}% name
  {Theorem}% title
  {%
    colback=green!5,
    colframe=green!35!black,
    fonttitle=\bfseries,
  }% options
  {thm}% prefix

\makeatletter
% ------------------------------------------------------------------------------------------
% User defined Commands
% ------------------------------------------------------------------------------------------

\newcommand{\reals}{\mathbb{R}}
\renewcommand{\qedsymbol}{$\blacksquare$}
\newcommand{\f}[1]{$f(#1)$}
\newcommand{\tcb@cnt@theoremautorefname}{Theorem}
\makeatother

% ------------------------------------------------------------------------------------------

\usepackage{footnote}
\usepackage{etoolbox}
\BeforeBeginEnvironment{theorem}{\savenotes}
\AfterEndEnvironment{theorem}{\spewnotes}

\begin{document}

\vspace*{13cm}

\begin{theorem}{Cauchy's Theorem}{}
Let C be a simple\footnote{A simple curve is one which does not cross itself.}. closed curve with continously turning tangents except possibly at a finite number of of points (otherwise curve must be smooth). If \f{z} is analytic on and inside C, then
\begin{equation}
\oint_{C} f(z) \, dz = 0
\end{equation}
\end{theorem}

\end{document}